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.Privilcaed nnd Confidential Midlcnd Plcnt Units 1 and 2 Public Hearing Testimony Diesel GenDrctor Building CHRONOLOGICAL LIST OF EVENTS BEFORE AND AFTER ISSUANCE OF NRC STAFF ORDER MODIFYING CONSTRUCTION PERMITS Date Activity October 5, 1977 Begin pouring the diesel generator building foundations to el 630'-6" December 13, 1977 Begin pouring the diesel generator building walls to el 635'-0" January 6, 1978 Diesel generator pedestal foundation (bay 4) is poured January 25, 1978 Completed pouring the diesel genrator building foundations to el 630'-6" (see October 5, 1977)
February 14, 1978 Diesel generator pedestal foundation (bay 3) is poured February 20, 1978 Completed pouring diesel generator building walls to el 635'-0" (see December 13, 1977)
March 8, 1978 Diesel generator pedestal foundation (bay 2) is poured March 14, 1978 Begin pouring walls to el 654'-0" March 23, 1978 Diesel generator pedestal foundation (bay 1) is poured April 28, 1978 Completed pouring walls to el 654'-0" July 10, 1978 -
Placement of heating, ventilating, and air con-August 22, 1978 ditioning chamber slabs at el 656'-6" August 22, 1978 NRC inspector at Midland jobsite is informed of unusual settlement of diesel generator building
- August 23, 1978 Diesel generator building construction voluntarily halted (
Reference:
BEBC-2427)
August 25, 1978 Soil boring program initiated September 7, 1978 Management Corrective Action Report 24 (MCAR) is issued September 29, 1978 Interim Report 1 to MCAR 24 is forwarded to the NRC i
Sheetil.,
W IPriviledged rnd Confidantinl Midlend Plant Units 1 and 2
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Public Hmering Testimony Diccal Generator Building Chronological List of Events (Continued)
Date Activity November 7, 1978 Interim Report 2 to MCAR 24 is forwarded to the NRC November 16, 1978 Construction activities resume on the diesel generator building (
Reference:
BEBC-2547)
November 16, 1978 Isolate electrical duct bank from the diesel generator building in bay 3 November 18, 1978 Isolate electrical duct bank from the diesel generator building in bay 1 November 21, 1978 Isolate electrical duct bank from the diesel generator building in may 4 Nove'mber 24, 1978 Isolate electrical duct bank from the diesel generator building in bay 2 December 12, 1978 Placed mezzanine floor to el 664
'0" in bay 4 December 19, 1978 Placed mezzanine floor to el 664'-0" in bay 3 December 20, 1978 Placed mezzanine floor to el 664'-0" in bay 1 December 21, 1978 NRC is informed (Howe 267-78) of decision to preload diesel generator building December 28, 1978 Placed mezzanine floor to el 664'-0" in bay 2 January 5, 1979 Interim Report 3 to MCAR 24 is forwarded to the NRC January 5, 1979 Commence pouring walls of building to el 678'-3" (see February 20, 1979)
January 12, 1979 End of pond fill January 26, 1979 Beginning of surcharging (completed on April 6, 1979).
Surcharge is placed in accordance with Specification 7220-C-81.
January 31, 1979 Condensate lines 20"-1HCD-169, 6"-1HCD-513, and 6"-2HCD-513 were cut loose on the south side of the turbine building.
Horizontal movement of 3 to 4 inches to the west was observed (see October 22, 1979.
Refer-ence:
field report)
February 1, 1979 Condensate line 20"-1HCD-169 was cut loose on the south side of the turbine building (see October 22, 1979.
Reference:
field reports)
Sheet 2
Privilederd and Canfidnntial
.Midlcnd Plcnt Units 1 cnd 2 Public H3sring Tastimony Diosol Generator Building Chronological List of Events (Continued)
Date Activity February 15, 1979 Preparatory work for installation of strain gage monitors in the turbine buildi.ng wall started today.
Strain gages are being installed in accordance with Specifica-tion 7220-C-83.
February 16, 1979 First crack mapping of diesel generator building is completed February 20, 1979 Completed pouring walls to el 678'-3" (started on January 5, 1979)
February 23, 1979 Installation of strain gage monitors for "Q" line wall of turbine building is completed.
Installation is in accordance with Specifica-tion 7220-C-83 (see February 15, 1979)
February 23, 1979 Interim Report 4 to MCAR 24 is forwarded to the NRC March 5, 1979 All surcharge activities through -Step III of Table I on Drawing 7220-C-1141(Q) have been
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completed.
Surcharge placement is suspended until March 22, 1979, to observe effect of surcharge placed to~date (surcharge approxi-mate elevation is 644'-0")
March 8, 1979 Commence placing roof and parapet to el 681'-6" (completed on March 22, 1979)
)
March 21, 1979 NRC initiates 10 CFR 50.54(f) Requests l
Regarding Plant Fill March 22, 1979 Placing of surcharge resumes in accordance
.with Step V of Drawing 7220-C-1141(Q) (see
' March 5, 1979.
Reference:
BEBC 2806).
Roof and parapet completed i.e.,
last of diesel generator has been poured (See i
March 8, 1979) 1 April 6, 1979-Placement of surcharge is completed (began on January 26, 1979)
April 24, 1979 Applicant submits response to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f)
April 30, 1979 Interim Report 5 to MCAR 24 is forwarded to the NRC May 31, 1979 Applicant submits Revision 1 of Responses to NRC Requests Regarding Plant Fill, i
L Sheet 3 l
Priviledgad rnd Confidential Midlcnd Plant Units 1 cnd 2 Public Hacring Testimony Diesel Generator Building Chronological List of Events (Continued)
Date Activity June 25, 1979 Interim Report 6 to MCAR 24 is forwarded to the NRC July 9, 1979 Applicant submits Revision 2 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f)
August 15, 1979 Removal of surcharge commences August 22, 1979 Construction activities resume on the diesel generator building August 31, 1979 Removal of surcharge is complete i
September 5, 1979 Interim Report 7 to MCAR 24 is forwarded to the NRC September 13, 1979 Revision 3 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to NRC October 22, 1979 Ann Arbor office allows field to reweld the condensate lines at the turbine building (see January 31 and February 1, 1979.
Reference:
BEBC-3344)
November 2, 1979 Interim Report 8 to MCAR 24 is forwarded to the NRC November 13, 1979 Revision 4 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to NRC December 6, 1979 NRC Staff issues Order Modifying the Construction Permits December 1979 Crack mapping of diesel generator buil-ding is again performed February 29, 1980 Revision 5 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to NRC April 1, 1980 Revision 6 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to the NRC May 5, 1980 Revision 7 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to the NRC Sheet 4 1
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,Privilrdq7d rnd Confid3ntini Midlcnd Plcnt Unita 1 cnd 2 Public H;cring Tastimony Dicsal Genarctor Building Chronological List of Events (Continued)
Date Activity August 1, 1980 North half of el 634'-0" slab is poured in bay 2 August 12, 1980 South half of el 634'-0" slab is poured in bay 2 August 15, 1980 Revision 8 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to the NRC August 15, 1980 North half of el 634'-0" slab is poured in bay 1 August 22, 1980 South half of el 634'-0" slab is poured in bay 1 August 29, 1980 Begin grouting the gap between the diesel generator building footing and the mud mat (see September 11, 1980.
Reference:
REM C-2817)
September 11, 1980 Completed grouting of gap between building footing and mud mat (see August 29, 1980.
Reference:
REM C-2817)
September 14, 1980 Revision 9 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is forwarded to the NRC October 8, 1980 North half of el 634'-0" slab is poured in bay 4 October 14, 1980 South half of el 634'-0" slab is poured in bay 4 October 16, 1980 North half of el 634'-0" slab is poured in bay 3 October 23, 1980 South half of el 634'-0" slab is poured in bay 3 October 31, 1980 Diesel generator has been installed in bay 1 l
November 13, 1980 Diesel generator has been installed in j
bay 2 November 21, 1980 Revision 10 of Responses to NRC Requests i
Regarding Plant Fill, 10 CFR 50.54(f) is submitted to the NRC Sheet 5
A 'Priviledgad and C:nfidential Midltnd Plcnt Units 1 cnd 2 Public Bacring Testimony Diesal Gensrctor Building Chronological List of Events (Continued)
Date Activity December 15, 1980 Diesel generator has been installed in bay 3 February 5, 1981 Diesel generator has been installed in bay 4 February 27, 1981 Revision 11 of Responses to NRC Requests Regarding Plant Fill, 10 CFR 50.54(f) is submitted to the NRC April 20-24, 1981 NRC performs Structural Technical Audit of Midland Nuclear Power Project July 1981 Crack mapping of diesel generator building is again performed 1
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Midland Plant Underpinning Questions Regarding Service Water Pump Structure Based on Submittals by Consumers Power February 25, 1982 1.
Design 1.1 How are spring constants selected for each loading condition?
What values are being used?
1.2 How much differential settlement is assumed in design for long-term conditien?
1.3 What maximum difference between load on each adjacent pier is acceptable to avoid breaking the shear keys?
1.4 For what out-of-plane forces has the underpinning wall beedcdesigded?
1.5 How is the shear load in the bolts estimated?
1.6 What are the existing maximum stresses and where do they occur?
1.7 Can SWPS support between corner piers? How much soil support is assumed.
2.
Dewatering 2.1 Provide description of dewatering system.
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2.2 Provide location, depths, and types of piezometers for monitoring water levels.
2.3 How long in advance of first drift will dewatering be done?
State that dewatering will be done well ahead of drift and e6 bcT d44 e1Gh cy
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Monitoring and Acceptance Criteria 2.1 Provide a table and plan that shows which cracks, pier loads, movements, and concrete stress charges will be monitored. State frequency of readings before, during and after underpinning.
For critical stages of underpinning, for example when first drift passes under structure and during installation of piers 1, 2, 3, 4, 5, 6, state frequency. Select the critical measurements and detail-how they..will.be used to control construction.
3.2 Provide a limiting criterion for each measurement.
3.3 How much time will pass between the measurement of a limiting reading and the action to prevent further distress.
WW. d4 3.4 For each case state remedial actiona tiat are intended if a limiting measurement is reached or exceeded.
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3.5 The use of 75% of predicted settlement as a criterion for judging whether settlement is occurring at a satisfactory rate is not applicable, since prediction may not be correct. This criterion should be celeted.
3.6 Jack loads and differential movements must be watched when sump is filled with water before jack removal.
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Bearing Stratum
_ [F 4.1 Who will accept the bearing stratum?
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4.2 How will adequacy of alluvium as a bearing stratum be. determined in situ. Why is lean concrete to be used under piers?
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4.3 What is maximum elevation difference of adjacent piers?
4.4 In one place it is, stated that a penetiometer under 150 # load i
is to penetrat 1/2' n.,, and in another 3/4 in. Which is correct?
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'S 4.5 Is there, prevalent gravel in the hard clay bearing stratum? Is YtS the material stratified?
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5.
Drift and Jacking 5.1 Why is drift under the structure rather than alongside?
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t 5.2' One pier should be load tested in detail to a value above the maximum expected hearing pressure, 5.3 Why is initial jacking-load not equal to full final load? If full load is left in place as long as possible settlement will occur for a longer period before jack removal.
5.4 Why are piers 11 built after removal of Jacks?
5.5 How often will loads on pier jacks be checked during underpinning.
6.
Admi..!I:2 ation 6.1 What is schedule of construction.
6.2 How much time will elapse between a critical measurement and remedial action.
6.3 Please provide flow chart showing expected sequence of activities, fc6 - f 01'; h fwufu a
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SUBJECT:
Review of the Technical Report nderpinning of the Service Water Pump Structure submitte Q t, 1981.
PREL mu M The Corps of Engineers has reviewed the subject technical report and has dis-cussed its comments with applicant in a meeting on 17 hoteJber. 1981, held in NRC office, Bethesda, MD.- Subsequent to this meeting, the applicant responded to the Corps' and NRC comments through its submission of_6_Nove_mbsr,_1981_.
The-Corps has reviewed the applicant response and has raised following questions:
Q1.
(Pg. 9, Sect. 3.3, Para. 1) Please provide a section through the wall l
showing how the settlement dial indicators would be attached to the btilding,and their probes connected to the permanent bench mark.
Q2.
(Pg. 9, Sect. 3.3, Para. 1) How will the settlement markers be monitored?
Section 3.2, as stated in the paragraph, does not provide the details of monitoring 4
of settlement markers.
Q3.
(Pg. 9, Sect. 3.3, Para. 1, last sentence)
From the last sentence of paragraph 1, it is apparent that some building movement will be allowed during the construction. Please provide details: _ bow much building movement at the free end of the overhang you plan to permit, and what is your basis for choosing a particular value of permissible building movement.
Q4.
(Pg. 9, Sect. 4) Please provic'e the details of bearing capacity analysis, shear strength parameters used, and resulting factor of safety for static and dynamic loadings.
Since the soils are highly overconsolidated, bearing capacity analysis bas,ed on drained shear strength parameters are also required.
Q5.
(Pg. 10, Sect. 5.0) Please explain variation in deformations of 0.2" over entire foundation, and how do you plan to incorporate the effects of these variation of deformations on the behavior of the structure.
If the soil media under the foundation are to be represented by springs, please provide spring constants and the method used in their determination with the details of the analysis.
Q6.
(Pg. 10, Sect. 6.1, Para 2)
Section DD of Figure 5, Reference 1, does not show details at the top end of the rod. Please provide a sketch showing the instrumentations to be used at the top of the piers to measure deflections of 4
the soils and the total top of the piers deflections.
Q7.
(Pg. 10, Sect 6.1, Para 2) Please explain the statement made in the last sentence of paragraph 2.
In our opinion, the difference between the soil deflection and total deflection at the top of pier will represent the behavior of the concrete in the pier rather than behavior of the supporting soil.
. Q8.
(Pg. 10, 11, Sect 6.1, Para 3) The predicted consolidaticn settlement is reported to be between 0.4 and 0.5 inches. We understand from Figure 4 that the above values of settlement include primary as well as secondary settlements.
Please provide details how were the,two components (Primary & Secondary) determined.
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3 Q9. Figure 4 shows that initial jacking loadings on the underpinning walls
)f, are much less than the final jacking loadings.
We understand that final jacking
( w loadings correspond to the total load of the structure to be transmitted to the y,
underpinning wall. Please provide basis for selecting lower initial jacki loadings and methods used in determining their values.
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Q10.
(Pg. 11, Sect. 6.1, Para 2)
Since piers will be constructe sequenc-ially, the initial jacking loadings must.be applied $2W Ulff,. Also, 'this is our understanding that 90 days time interval between initial and final jacking g{
' loadings must be counted from the date when initial jacking has been applied to
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the last pier (pier No. 12). Please provide your discussion on this aspect.
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(Pg. 11, Sect. 6.1, Para 2) Please provide details to substantiate
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8 Q the statement, "At about 110 days, the curve will flatten so it will appear as D
a straight line,on this semi-log plotting." It appears that only 20 days (110-
~ 90) have been allowed for primary consolidation to complete after application of final jacking loadings.
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(Pg. 11, Sect. 6.2) What is acceptable limits of settlement rate?
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How have you determined these limits?
f; Q13.
(Pg. 12, Sect. 8.0) What is basis for selecting 2" of deflection at which soil indicate plastic behaviors. Also, provide basis for.01" settlement g.
in 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after 3 days of constant load, and.02" for interval 10 to 20 days under constant load.
p\\t5 Q14.
(Pg. 12, Sect. 9.0) Please provide plan showing the location of g piezometer to be installed for monitoring ground water levels during construction.
Q15.
(Pg. 13, Sect. 11) The soil spring constants have not yet been 4
received.
Q16.
(Pg. 8, Sect. 3.1.1)
By constructing first pier #4 and pier #5, and then preloading them with initial jacking' loads, the symmetrical application jacking loadings on the structure will be violated.
Please explain what will be the consequence $of unsymmetrically applied jacking loads?
Q17.
(Pg. 8, Sect. 3.1.2)
In our opinion, the measurement and the con-sideration of the loadings on pier Nos. 1, 2 and 3 alone would not provide sufficient information about structural problem encountered during construction.
The construction of tunnels from piers 3's to piers 4's would transfer.me addit-ional load to piers 1, 2 and 3 which ultimately be transferred to the structure by cantiliver action because of increased settlement of tops of piers 1, 2 and 3, and as such, the stress recording device placed on top of the piers may not be able to record these additional loadings.
Therefore, settlement of the piers must be monitor with utmost care and be used in determining the construction procedure.
Q18.
(Pg. 8, Sect. 3.1.3) The allowable bearing intensity for foundation should be determined using the test results of samples for COE-16.
Please revise and furnish the new values instead of 19.2 ksf bearing intensity and.1600 kips 6
bearing load for each pste group.
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(Pg. 2, Sect. 2.1.1.2, Para b) The long term shear strength parameter given in this paragraph is not consistent with,?ro,m zone of influence of the Woodward-Clyde consultants' test data. As'a matter of fact, no sample has been g foundation.
Q20.
(Pg. 3, Sect. 2.1.2.1)
Since the jacking used during the final load transfertuould only transfer the dead and the equipment load of the fill supported structure on the foundation media of the underpinning walls and those of structure originally founded on natural soil, it would not produce load on the foundation more than the total structure load of the overhang portion. Therefore, any load transfer caused by jacking should be considered as dead load and in loading com-bination'in design of foundation and structure should be considered as dead load.
Please explain why in one of the loading combination on page 3, it has been con-sidered separately.
Q21.
(Pg. 3, Sect. 2.1.2.2, Para c) Please explain the statement made in para. c.
It is not known why the foundation of underpinning wall would not carry the dead load and live load?
Q22.
(Pg. 4, Sect. 2.1.3.3)
Does the bearing pressure 8.12 ksf include the effects of post tensioning the overhang structure? How did allowable bearing pressure of 16.7 ksf was determined?
Q23.
(Pg. 4, Sect. 2.1.4.1)
Why other loading combinations as used for lower foundation slab have not been verified in this care?
Q24.
(Pg. 6, Sect. 2.1.6.2)
Please explain why Pt has not been considered as dead load in loading combination used and shown in paragraph c.
Q25.
(Pg. 6, Sect. 2.1.6'.3)
Please provide shear, capacity of each 2" dia.
rock anchors.
Please, also provide the magnitude of horizontal shear at the interface of underpinning walls and the bottom of the existing foundation slab.
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Q26.
(Pg. 7, Sect. 2.1.7.1)
Why appropriate load factor has not been used in design of underpinning walls?
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Subject:
Design Issues to be Audited by HGEB at February 3-5, 1982 Audit in Ann Arbor, Michigan Lic:nse Documentation Anticipated to be Condition No.
Review Issue Presented to HGEB Design Audit Feb. 3-5, 1982 Sa Auxiliary Building Plan and sectional views showing the locations Information was provided in Temporary Support in the structures and on the foundation bearing Dasgupta presentation and System During layer where temporary underpinning loads have handouts, but results are Underpinning resulted in the largest stresses.
Drawings impacted by the requested (EPA and Control should indicate assumed exc. conditions at sensitivity study on soil Tower) the various stages of construction, spring constant variations.
Calculations that provide the magnitude of Checked by SEB the above stresses.
Calculations providing the factors of safety Provided in Dasgupta against bearing failure.
Presentation 5b Auxiliary Building Sketches showing deformation measuring Provided by Bob Adler.
NRC Temporary Support instruments attached at top of pier at the needs to review System During selected locations.
Underpinning (EPA & Control Description of frequency of readings to be Provided on drawing entitled Tower) required.
" Instrumentation Matrix" Identification of the ALLOWABLE movements, Criteria given for FIVP strains or stresses at the selected monitoring piping. Tolerance criteria locations and CALCULATIONS which are the basis on movements is still for those allowable movements. What are required for both Phase II crack monitoring plans?'
and Phase III instrumentation.
Criteria to be followed for READJUSTING Criteria on jacking is jacking load (? Settlement).
controlled by both settlement and stress considerations CPC to provide drawings, procedures and criteria to NRC on Feb. 26, 1982.
a-Pagg 2 LicGnse Documentation Anticipated to be Csndition No.
Review Issue Presented to HGEB Design Audit Feb. 3-5, 1982 Sb This is ALLOWABLE movements. What valves Tolerance criteria will-(continued)
(limiting) of movement or cracking or stress identify both an action -
will require re-evaluation and stopping c' level and a stopping level.
underpinning? How established? Provide CPC still needs to address the time interval (maximum) between crack propagation. NRC observing limiting movement or stress needs to review criteria and time for action (re-evcluation or on cracking provided in stopping).
Auxil. Bldg. report and be prepared to discuss at Feb. 25, 1982.
Sc NRC Testimony Previous discuss (ons have resolved this Previously resolved.
(11/20/81) issue. 1, Q.6 Sc 1, Q.7 Provide explanation on how measured jacking By knowing the shape, load and pier settlement will be used in embedment, deflection -
NAV-FAC DM-7, Fig. 11-9 to establish Fig. 11-9 is used to i
equivalent soil modulus.
establish coefficient which i
permit 5 modulus ~to be l
computed.
Issue is resolved.
i Sc 1, Q.17 Provide CALCULATIONS which determined the 9 Pier W5, the Turbine Bldg i
k magnitude of the test' load for temporary support load is 878,
pier. What part of this load is due to Total load is 2513k Turbine Bldg. and what part is due to EPA?
(maximum).
i (Is this a location of large stress which has been covered in Lic. Cond. Sa?)
3 Sc 1, Q.18 Does previous discussion under license Refer to status of Sb.
condition 5b on ALLOWABLE movements cover Q.18?
Sc 1, Q.19 Question has been adequately addressed Previously Resolved.
including discussions at last audit of s
j Jan. 18-20, 1982.
4
Page 3 License Documentation Anticipated to be Condition No.
Review Issue Presented to HGEB Design Audit Feb. 3-5, 1982 Sc 1, Q.20 Previous discussions have resolved Previously Resolved this issue.
Sc 1, Q.21 Describe what makes up the working load Working load = DL + Eqpt.
and calculations that establish it.
loads + 25% LL + wt.
Explain basis for 1.25 times the block wall working load = Proof load.
Provide calculations on resistance capacity Proofload = Working load of the EPA.
+25% working load Capacity of pier W8 is 4000 Kips Sc 1, Q.22 Provide magnitude of jacking load for
~ Jacking loads provided in each control tower pier and ratiked Dasgupta presentation.
to establ.ish it.
Refer to CPC Auxil. Bldg testimony, Refer to previous response Pg. 24.
Describe criteria for monitoring to license condition no. Sb jacking loads on Control Tower (if not for jacking criteria, covered in 5b). What method will be used Anticipate maximum & minimum to assurance maintenance of jacking loads on loads will be provided by Control Tower? Request further discussion Feb. 26, 1982.
on load transfer beyond response to Q.22.
Load transfer to final underpinning wall to be covered in May 1982 Audit.
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.t CONSTRUCTION CONDITION 8
- PARAMETRIC STUDY e Effect of Soll Modulus Variation e All0WABLE SETTLEMENTS
- ADMINISTRATIVE PLAN OF ACTION
- GAP BETWEEN TURBINE AND AUXILIARY BUllDINGS o
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MOOLANO UellTS 1 ANO 2 AUMILIARY DUILDetfG UtetMPetsNf 980 2/23/02 G 198412
XUXILIARV BUILDING UNDERPINNING 2
3 EXISTING SOIL SPRINGS UNDER AUXILIARY BUILDING (concrete modulus =
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BIPE, MRJD, MAIHA - Determines necessity of corrective
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- BIC 'IM. PLEMENTS PROJECTENGINEERING (BIPE) DIRECTIVE I
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' AUXILI A RY SUILDING UN DE.RP'INNIN -
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ADMINI ST R ATIV E.
PLAN FOR XCTloN i.
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ADMINISTR ATIV E PLAN FOR ACTION (S U t LDING CRACK Mo M IT'o lt. ins)
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f MEMORANDUM FOR:
C. C. Williams, Chief, Plant Systems System
.2. d +e D/
FROM:
R. B._ Landsman, Reactor Inspector
SUBJECT:
INSPECTION PLAN FOR MIDLAND gg
- R*
Cy%
Ct4 "*w ~ol enw Observation of work, specifications, design drawings, work proce ures, refY/q QC inspection procedures and QA overinspection procedures will be reviewed-for the following:
MLMj V8's 5
? __.
Dewatering wells.
Drawdown - Recharge test.
/,
BWST surcharge program.
[
Benchmark installation.
p Freeze-wall installation.
D.G. building crack repair.
BWST remedial fix.
Underground pipes.
Service water pump structure remedial fix.
Auxiliary building remedial fix.
Furthermore, each item listed is many faceted requiring approximately two months each. For example, the auxiliary building fix includes access shafts, a tunnel under the turbine building, concrete support piers, horizontal drifts under the control building, grillage support beams under the control building, mass excavation, permanent foundation and backfill.
a
1
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Additionally, personnel' qualifications for QA/QC will be reviewed taking.
approximately one week. A month is required for audits of laboratories,.
underpinning contractors and Bechte'l Ann' Arbor.
Furtherrnore, around a month is needed for hearings and meetings.
1 l~
James W Cook Vice Pressdent - Projects. Engsneerrng and Constructson General offices: 1945 West Parnail Road. Jackson. MI 492o1 + (517) 788-o453 February 16, 1982 Harold R Denton, Director Office of Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 MIDLAND PROJECT MIDLAND DOCKET NOS 50-329, 50-330 EVALUATION REPORT FOR CONCRETE CRACKS IN THE DIESEL GENERATOR BUILDING FILE 0485.16 SERIAL 15978 ENCLOSURE:
EVALUATION OF THE EFFECT ON STRUCTURAL STRENGTH OF CRACKS IN THE WALLS OF THE DIESEL GENERATOR BUILDING.
~
On December 10, 1981 and January 11, 1982, meetings were held with the Staff and its consultants to discuss concrete cracks in the auxiliary building, the 9
service water pump structure, the diesel generator buildings and the feedwater isolation valve pits.
During the January 11, 1982 meeting, Consumers Power agreed to provide the NRC with an evaluation of the significance of concrete cracks relative to the design strength of the diesel generator buildings.
In response to this commitment, we are providing the enclosed report entitled
" Evaluation of the Effect on Structural Strength of Cracks in the Walls of the Diesel Generator Building" by Dr. Mete A Sozen, Professor of Civil Engineering at the University of Illinois-Urbana.
We also call your attention to of the enclosed report which was contributed by Messrs.
WG Corley and A E Fiorato of Construction Technology Laboratories, a Division of the Portland Cement Association.
Both Dr. M A Sozen and Dr W G Corley are members of the American Concrete Institute (ACI) Committee 318 on standard building code.
The enclosed report presents an evaluation of the significance of the cracks observed in the diesel generator building.
The information, measurements and test data presented in the enclosed report leans further support to our conclusion that:
9 1.
At an intermediate construction stage with'the foo' ting resting on the duct bank, normal horizontal tensile stresses in the walls would have caused the cracks near the duct banks, if those cracks had not occurred earlier in fresh concrete.
2.
There is no evidence to indicate that the strength of the building is less than that assumed in its design.
oc0282-0026a100 f EB 22 N l
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WP 3.
2
. Based upon the information contained in the enclosed report, we wish to emphasize that the function of the diesel generator building is well within the range of the experience which supports the theory and practice of
~ reinforced concrete building construction.
Therefore, there is no need to reanalyze the diesel generator building using a model to reflect the effects
-of tensile discontinuities implied by the concrete cracks.
MC4 Mooney Executive Manager Midland Project Office For J W Cook JWC/RLT/mkh CC Atomic Safety and Licensing Appeal Board, w/o CBechhoefer, ASLB, w/o MMCherry, Esq, w/o FPCowan, ASLB, w/o RJCook, Midland Resident Inspector, w/o RSDecker, ASLB, w/o SGadler, w/o JHarbour, ASLB, w/o GHarstead, Harstead Engineering, w/a DSHood, NRC, w/a (2)
DFJudd, B&W, w/o JDKane, NRC, w/a FJKelley, Esq, w/o RBLandsman, NRC Region III, w/a l
WHMarshall, w/o JPMatra, Naval Surface Weapons Center, w/a W0tto, Army Corps of Engineers, w/a WDPaton, Esq, w/o SJPoulos, Geotechnical Engineering, w/a FRinaldi, NRC, w/a HSingh, Army Corps of Engineers, w/a BStamiris, w/o i
4 oc0282-0026a100 f
PEgy.
~
+
ENCLOSURE EVALUATION OF THE EFFECT ON STRUCTURAL STRENGTH OF CRACKS IN THE WALLS OF THE. DIESEL GENERAT0h BUILDING MIDLAND PLANT UNITS'l AND 2 MIDLAND, MICHICAN l
l-A Report to BECHTEL ASSOCIATES PROFESSIONAL CORPORATION Ann Arbor, Michigan i
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by l
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Mete A. Soren 503 W. Michigan Urbana. IL 61801 11 February 1985 l
I kA wund 0
93 m.
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CONTENTS
SUMMARY
1 3-INTRODUCTION.
4 DIESEL GENERATOR BUILDING WALL STRESSES CAUSED BY TEMPORARY SUPPORT FROM THE DUCT BANKS 6
RESIDUAL STRESSES 10 EFFECT OF EXISTING CRACKS ON WALL STRENGTH.
14 FIGURES ATTACHMENTS 1.
Crack Development in Reinforced Concrete 2.
Effect of Existing Cracks en Strength of Reinforced Concrete Members 3.
Cracks in Concrete Walls 4.
Evaluation of Cracking in Diesel Generator Building at. Midland Plant by W. G. Corley and A. E. Fiorato s
6 0
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SUMMARY
This is a study of the eff ect on strength of the cracks on the walls of the Diesel Generator Building, a box-like reinforced concrete structure with overall dimensions of approximately 70
- 155 by 50 f t high.
The exterior walls are 30-in. thick. Three 18-in. thick interior walls with their longitudinal axes in the short plan dimension of the building divide the building into four cells of approximately equal size (Fig. 1 and 2. ).
In addition to typical volume-change cracking, some of the interior walls and the east exterior wall have been observed to contain systematic crack patterns (Fig. 6) near the locations of the duct ' banks (Fig. 4).
The duct banks had provided unintended temporary supports for the walls in construction because of settlement of the fill on which the building is founded.
Stress conditions in an interior wall during an intermediate construction stage are analyzed. Residual crack widths and patterns are evaluated.
Background information on cracking and strength of reinforced concrete structures is provided in Attachments 1 and 2.
The study concludes that:
(1) At an intermediate construction stage, with the footing resting on the duct bank, normal horizontal tensile stresses in the walls would have caused the cracks near the duct banks, if those cracks had not occurred earli'er in fresh concrete.
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2 (2) Residual tensile stresses'in wall reinforcement are likely to be less than 30 ksi and certainly in the linearly elastic range of the Grade 60 reinforcement.
(3)- There is no evidence to indicate that the strength-of the building is less than that ~ assumed in its design.
It should be emphasized that the function of the Diesel Generator Building is well within the range of the experience which supports-the' theory'and practice of reinforced concrete building construction.
The existence of discontinuities in the concrete is a condition
- anticipated by ordinary methods of design for reinforced concrete structures.
A crack in a concrete wall or beam is not comparable to a discontinuity in, for example, a steel plate girder. Continuity in tension of reinforced' l
concrete structures is effected not by the concrete but by the reinforcing l
bars. Therefore, there is no need to reanaly'ze the building using a model to reflect the effects of tensile discontinuities implied by the cracks.
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INTRODUCTION The walls of the reinforced concrete structure to house the emergency ' diesel generators for the Midland Power Plant Units 1 -and 2 have-been observed'to have developed cracks ranging in width up to a.
recorded maximum of 0.028 in.
The object of this report is to scudy the widths and arrangement of the cracks to determine the conditions -leading to cracking and the possible consequences of the existing cracks on the strength of the structure.
This report was written at the request of Bechtel Associates Professional Corporation, Ann Arbor, Michigan.
In addition to a visit to inspect the Diesel Generator Building, the writer had access to information provided in the following Bechtel documents:
(1) Crack mapping sheet 1, February 1980.
(2) Drawing showing cracks surveyed in July 1981.
(3) Drawing SKC-616 showing progress of concrete casting for the Diesel Generator Building.
(4) Drawings C-1001 through C-1039 showing concrete outlines and reinforcement details.
(5) Response to NRC Question 14, containing a figure showing crack patterns in the walls of the Diesel Generator Building (dated i
24 April 1979).
(6) Respons,e to NRC Question 28, containing a figure,differpntiating cracks surveyed during December 1978 a'd cracks surveyed after' n
September 1979 (dated February 1980).
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4 (7) ~ Response to NRC_ Question 40.
DIESEL GENERATOR BUILDING The Diesel. Generator Building is a stiff box-like structure cover-ing an area of approximately 70 x 155 ft.
Its plan and sections are shown in Fig. I and 2.
Exterior walls are 30-in. thick. The interior space is divided into four cells of approximately equal size by three 18-in. thick interior walls running north-south. All interior and exterior walls are supported by continuous strip footings (10 by 2 ft 6 in.
in cross section). The walls rise from an elevation of 628 (bottom of footing) to 680 (cop of roof slab). The long exterior walls on north and south sides of the building have various openings as in'dicated in Fig.
1.
The design compressive strength for the concrete in the walls was 4000 psi. Uniformly spaced wall reinforcement is provided by Grade 60 No. 7 (interior wall) and No. 8 (exterior wall) bars at 12 in. each way near each face of wall. The uniform reinforcement ratios in both the horizontal and vertical directions are 0.567. for the interior and 0.447 for the exterior walls.
Because it houses the generators to provide power in an emergency, the Diesel Generator Building is classified as being in Seismic Category I.
The building must maintain its integrity if subjected to an earthquake motion having an intensity equal to that of the motions postulated for the " safe shutdown earthquake (SSE)."
It must also resist forces and missiles generated by tornados.
The. building is founded on plant fill. Casting of the concrete structure was started in October 1977. Because the observec sectiement
+
5 of the building exceeded the estimated amount, construction was halted during August-1978. At the time the construction was stopped, walls had been completed to an elevation of approximately 662. Distribution of the settlement observations made indicated a slight " tilt" of the building, the southwest corner settling perceptibly more than the northeast corner. It was reported that the fill was settling away from the building under the footing of the east wall. These phenomena suggested that the duct banks (Fig. 3 and 4) had made contact with the footings of the interior walls and the east wall.
In November 1978 the duct banks were separated from the footings.
Changes in settlement are illustrated schematically in Fig. 5.
Construction was resumed in December 1978. To ameliorate future settl'ement of the fill.
a surcharge (approximately 20 ft of sand) was placed to cover the construction site. The structure was completed in April 1979. Surcharge i
was removed in August 1979.
l l
Figure 6 shows the cracks observed in December 1978 on the surfaces of the north-south walls up to an elevation of 664.
A cursory review of the crack patterns suggests their compatibility with the settlement history l
of the structure. Cracks on the west wall, which did not have a duct bank belcw it, are of the type clearly attributable to ordinary volume-i change effects of the concrete. On the other hand walls with duct banks beneath them have some cracks which imply a systematic stress pattern attributable,tg a support placed near.the position of the duct banks.
The cracks observed in the center wall provided the strongest indication i
of the pressence of such a support. The cracks shown in Fig. 6 are
6 those whica were measured-to,have widths of'at least 0.01 in.
Maximum crack width measured was reported to be 0.028 in.
After the duct banks were separated.from the footings there was observed a general' reduction in width of the larger cracks near the' duct banks.
Cracks on the north and south walls of the Diesel Generator Building were generally smaller in width. Their distribution indicates that they were caused primarily by volume-chan5e tendencies of the concrete.
WALL STRESSES CAUSED BY TEMPORARY SUPPORT FROM THE' DUCT BANKS A schematic representation of the-center wall is shown in Fig. 7 Soil reaction on the footings is represented by a series.of springs.
The effect of the duct bank, after it comes into contact with the bottom of the wall footing, is it.:erpreted as a reaction provided by a very stiff spring.
Consider a particular stage during the construction of the wall.
Concreting of portions A and B has been completed, in that order, within a few days of each other. Approximately two weeks later, after the concrete in portions A and B has hardened. Lifts C and D are placed in succession.
Because of the eccentricity of the reaction provided by the duct bank, the building is likely to tilt to the south as it settles. A ilmiting condicon is one in which the portion of the wall north of the duct spring is lifted off the springs representing soil reaction. Load-dependent stresses in
. the wall corresponding to this limiting condition may be estimate'd from an analysis of the stresses in a linearly clastic model of the " cantilevered" portion of the wall shown in Fig. 8.
y-7
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The elevation and section shown in Fig. 8 represent the hardened concrete in portion A of the center w.11 up to elevation 650 (Fig. 7).
It is assumed that the reaction of the duct bank may be concentrated as a line load at a point 22 ft from the inside face of the north wall, as shown in the lower left-hand corner of the wall elevation. The horizontal links represent the restraint of the rest of the w.11 to the south of the support.
The pressure of 12.5 psi on the upper surface of the wall represents the effect of the fresh concrete in lift C (Fig. 7).
The edge load represents part of the weight of the north wall. When included in the analysis, it was applied along the vertical edge uniformly
~
except for a heavier concentration at the top to represent the weight of fresh concrete above that level.
Young's modulus of the concrete was assumed to be 4
- 10 psi.
Poisson's ratio was taken as zero. Density of reinforced concrete was set at 150 lb/ cubic ft.
Internal stresses were analyzed for two conditions:
(a) for zero edge load and (b) for a nominal distributed edge load of 200,000 th.
In both cases self-weight and pressure on top surface were included.
Horizontal stresses calculated on a vertical plane one foot away from the left face of the wall segment (fixed edge) considered are plotted in Fig. 9 for both solutions.
The tendency of both tensile stress distributions to increase near.
the effective neutral axis is due the " bursting" stresses caused by the concentrated reaction at the bottom flange.
C w
8 The reason for showing two stress distributions in Fig. 9 is to emphasize the indeterminacy of the actual loading conditions on the wall.
The edge load could be considerably higher than that assumed. The range of the calculated tensile stresses suggests that stresses of a magnitude to cause cracks in the hardened concrete would have existed in the wall in the vicinity of the duct bank at a time when the concrete in lifts C and D (Fig. 7) was fresh.
It is important to note that the analysis above demonstrates that cracking would have occurred after casting of lifts C and D but it does l
not preclude the appearance of cracks to accommodate settlement deformations before that stage in construction.
In reference to Fig. 7, it will be appreciated that stress-related cracking depends on resis'tances and stiffnesses (strength and stiffness of the concrete as well as the stiffnesses of the duct banks and the supporting soil) which are all i
time-dependent. Complex as these combinations are, they are further complicated by construction events. To reconstruct the stress / strength interaction loading to cracking of the concrete is virtually impossible but also unnecessary.
If no cracks had formed before the construction stage considered, calculations indicate that cracks would have formed then and consistently with the observations of settlements and crack patterns.
In relation to the observed phenomana, it is of interest to investigate the progress of a crack in the wall once it is initiated.
Figure 10 shows the reinforcement in the wall segme't considered n
above. The relationship between crack height'and resisting moment was determined assuming a direct tensilestrengthof4/f[forthe4000 psi e
O
c
^
9 concrete. Yield stress of all reinforcement was assumed to be 60,000 psi. Calculations were made with the bottom edge of the wall in-compression.
The calculated relationship-is plotted in Fig. 11.
It illustrates two inherent' features of crack development in a reinforced section subjected to flexure.
It is noted that at'ter cracking occurs at a moment of approximately 8,500 kip-feet, there is a drop in resistance. Theoretically, the crack would penetrate almost to the flange (the footing) before the section redevelops a moment of comparable magnitude.
Even though the wall is adequately reinforced (o = 0.0056), the reinforcement is distributed over its height rather than'being concentrated near the extreme fiber in tension. Consaouently, the flexural crack penetrates deeply into the section before sufficient reinforcement force is mobilized to compensate fur the loss of the tensile strength of the concrete.
It may also be noted from Fig. 11 that after the crack penetrates about 12 ft into the section, the slope of the curve becomes positive.
Its progress is controlled after a penetration of approximately 17 ft.
Equilibrium of internal forces and external effects is re-established.
The extent of the cracks observed especially in the center wall is quite consistent with the expected behavior of reinforced concrete sections subjected to flexure.
It should, however, be remembered that the walls of the Diesel Generator Building are not likely to be subjected to O,
r 10 flexural stresses of this magnitude in their normal function because the duct banks have been separated from the footings and because the building is now complete. The overall depth of the section is now ever 50 fc rather than 22 ft as considered in the calculations.
RISIDUAL STRESSES Figure 10 shows the trajectories of the cracks recorded in July 1981 on east face of the center wall. Cracks shown are those having widths of 0.01 in. or larger. East face of the center wall was chosen for study because it had more and wider cracks than the other walls.
The maximum crack width at the time of the July 1981, survey was reported to be 0.02 in.
This is less than the maximum of 0.028 in.
observed earlier. The reduction in width is consistent with the result of the calculations in the previous section which supported the observation that bending stresses caused by the temporary concentrated support contributed to crack formation. Separation of the duct banks from the footings would cause the wall cracks in the vicinity of the duct banks to reduce in size. On the other hand, these cracks would not be expected to close completely because the concrete surfaces bounding the cracks are likely to fit perfectly ar.d because the foundation profile is not not likely to have returned to precisely the shape it had before opening of the cracks.
It should also be remembered that crack-width measor'ements made at
~
different times may differ.
In addition to the natural scatter in In a CTL survey made in February 1982 (Attachment 4) a maximum width of 0.025 in. was recorded on the center wall.
O
11 observation,' changes in temperature and humidity may affect the size of the cracks within a short period of time. The small variation in maximum observed crack width from 0.028 ro 0.02 in. is consistent with what would be anticipated, given the history of the building.
An estimate of the residual stress in the wall reinforcement may be obtained from the residual crack widths. A brief perspective of the information on the relationship between tensile reinforcement stress and crack width is provided in Attachment 1.
Crack width estimates or measurements are used typically to make judgments about serviceability _
i and/or durability of a reinforced concrete structure.
For that task, the role of the crack-width estimate as an index value is relevant and l
useful. But the relationships which yield an estimate o'f the crack width as a function of steel stress, concrete cover and other variables are F
not typically used in reverse to determine stress from width measure-ments. Used for that purpose, they may help provide information as to whether and to what extent yielding may have occurred at a given location.
l l
Any quantitative inference made on that basis must be treated as a very l
rough measure.
L It was stated in the previous section that the cracks related to the support from the duct bank could have occurred before concrete in portions A and B (Fig. 7) hardened.
In the following discussion, it will be assumed that cracks occurred in matu,re concrete'and within a short period of time, thus leading to upper-bound estimates of residual stress in the reinforcement.
O
12 i
The simplest and most direct method for estimating steel stress from crack-width data is to use the data simply as a measure of bar extension.
i l
Crack widths were measured at two levels on the east face of the-center wall (Fig.12). Widths measured at the upper level (elevation of approximately 645) are seen to add to a larger sum than those in l
l the lower level. Considering the sum of crack widths at the outer level-between two 0.02-in. cracks indicated by the letter B and assuming that l
f the one crack not measured at that level had a width of 0.01 in. as l
measured at the lower level, the total extension is found to be approximately 1/8 in.
The length, L, over which this extension is g
i assumed to have taken place is approximately 150 in.
T' e corresponding '
h strain, e,, is approximately 0.008 and the related steel stress 3
f, = c,
- E, = (.125/150)
- 29
- 10
= 24 ksi i
l Considering the reliability of the crack width measurements and t!1e probability of the very small cracks in this area not being reported, j
rhe plausible conclusion from this attempt is that the residual stress
(
would be in the range 20 to 30 ksi if the crack occurred in mature concrete.
1 The strong inference is that the reinforcement is in the linear (elastic) l range of response.
- To obtain another perspective of the residual sto'el stressos in l
1 relation to crack widths, it is instructive to attempt a calculation of t
i 13 the crack width using a predictor expression of the type described in.
The conditions under which stress-related cracking is
. assumed to have occurred in the walls of the Diesel Generator Building are not typical of conditions in beams. Therefore, the predictor expression chosen is one developed by Holmberg and Lindgren (Attachacet
- 3) from data obtained using wall elements in direct tension. Using the metre as a unit of length. Holmberg and Lindgren give the mean crack spacing.
L,. for a wall '(with all bars having the same diameter) as 1, = 0.055 + 0.144 (A,/db l
where i
A, = is the " effective" concrete area around the bar i
db = bar diameter Holmberg and Lindgren tested wall segments with centrally located l
reinforcement in a specimen thickness representing twice the cover of t
the bars in the wall. Adopting their approach, for bars spaced at 12 in.
with the distance from center of bar to near face of wall assumed to be i
2.5 in.,
l f
A, a 12
- 5 e 60 in = 0.039 m resulting in
&, = 0.055 + (0.144 *.039/0.022) = 0.31 m (ipprox. one'it) 9 O
0 4
14 To obtain an estimate of the characteristic crack spacing, Holmberg and Lindgren multiply the mean calculated crack width by 1.4 To obtain the corresponding maximum crack width, a magnification factor (based on statistical data on crack width distribution) of 1.7 is used.
For the walls of the Diesel Generator Building the maximum calculated crack width j
for a stress of 20 kai would be I
3
-3 1.7
- 1.4
- 0.31 * (20/29 = 10 ) = 0.5
- 10 m
w*
= 0.02 in.
l This result indicates that, on the basis of the experimental data obtained by Holmberg and Lindgren, the wall considered (for concrete l
cover and reinforcement amount specified) would be expected to develop i
a maximum crack width of approximately 0.02 in. for a bar stress of 20 kst.
/ i.
The calculations using the Holmberg-Lindgren expression confirm that a maximum residual crack width of 0.02 in. in the walls of the Diesel Generator Building implies a residual reinforcement stress of loss than 30 kat, well in the linear range of response of the Grade 60 reinforcement.
EFFECT OF EXISTING CRACKS ON WALL STRENGTH l
l Reinforced concrete structures are designed and built with the L
explicit assumption that concrete will crack. Appe4rance of cracks on structural components of a retnidrced concrete butiding provide no cause for re-evaluation of the strength of the structuro untoss the cracks 1
15 indicate general yielding or are related to imminent failure in shear or bond. Attachment 2 contains a discussion of the strength and behavior of "precracked" reinforced concrete structures, or elements with cracks which occurred before the application of a particular loading program.
Field observations and the analysis in this report indicate that cracks in the walls of the Diesel Generator Building were caused generally by ordinary volume change effects and locally, in some of the north-south walls, by tensile stresses resulting from temporary support of the duct banks.
Analysis of the stress conditions created by the temporary supports indicates that cracks could have occurred in fresh concrete during the setting of concreto in portions A and B of the center w'all (Fig. 7) or, if it did not occur then, in mature concrete after the casting of lifts C and D.
In either case, the cracks would be related primarily to bending deformation. There is no evidence, visual or analytical, to attribute the cracks to shear or bond-failure mechanisms.
All available evidence indicates that the residual stresses in the wall reinforcement are well within the linear (elastic) range of response of the material. Furthermore, residual reinforcement stresses associated with the existing cracks are on planes unlikely to be subjected to high normal tensile stresses under postulated design-load combinations.
.The function of the Diesel Cenorator, unlike that of a containment vessel, is within the experienco rocord which has lod to the theory and practice of reinforced concreto construction. There is no reasonable 4
e
16 cause for concern about the consequences of the cracks in question, except for protection of the steel from any unusual aggressive environ-Examples of the behavior of reinforced concrete elements subjected ment.
to axial load, bending, and shear after having been cracked as a result of other loading conditions are provided in Attachment 2.
Currently, there is no indication that the strength of the walls of the Diesel Generator Building is less than that assumed in the original design. Design methods for reinforced concrete structures have been based on the assumption that concrete does not provide resistance to normal tensile stresses. The presence of cracks in the walls of the Diesel Generator Building does not represent a condition which would' require l
special procedures for modeling the existing structure..
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ATTACHMENT 1 CRACK DEVELOPMENT IN CONCRETE Summary This attachment has been prepared to provide a perspective of the development and use of predictor expressions for crack width.
Derivations of the two common types of predictor expressions are described and a specific example of each type is used to calculate crack widths for a test beam.
Introduction Tensile strength of concrete made with normal weight aggregate is approximately a tenth of its compressive strength. The low strength in tension is not compensated by a low Young's modulus.
Initial modulus of concrete in tension is comparable to its modulus in compression.
Furthermore, the limiting strain in tension is also low, approximately 0.0002. These properties combine to make concrete quite susceptible to cracking.
Cracking is not necessarily related to stresses generated by loads or externally imposed deformations. Much of the cracking in elements having low apparent stress levels is caused by time / temperature dependent volume changes or by chemical reactions causing local deformations (such as rusting of embedded reinforcement or expansion of aggregates).
In general, cracks unrelated to load or imposed deformations are attributable to restraints on dimension change'resulting from heating / cooling or expanding / shrinking.
e 4
l i
1.2 Limiting the' perspective to phenomena in one dimension only, a qualitative understanding of events leading to a crack as a result of volume change may be obtained with the help of Fig.
1.1.
The concrete prism ABCD is assumed to be perfectly insulated on faces AD and BC as well as on faces parallel to the plane of the paper so that there is no loss of heat and moisture on those faces.
It is also assumed that there is no external restraint on any face of the prism.
At a given time after the concrete-is cast, the unreinforced concrete prism ABCD may be expected to assume the shape described by the broken lines. The change in shape is the result of differential shrinkage (moisture content in regions closer to the free boundary is expected to diminish at a faster rate) or thermal gradient (assuming in this case an ambient temperature on the free boundary lower than that at longitudinal axis of prism, a typical state during setting of cement).
Considering the thin planar element PQRS, it is concluded from the free-body diagram in Fig.1.lb that restraint forces along RS will result in a tensile force on edge QR.
Because it is produced by dimensional changes varying with time, the tensile stress on edge QR varies with time. The effective tensile stress, represented by the broken curve in Fig.1.2, is the result of a complex interaction among variations with time of shrinkage, temperature, stiffness modulus, and creep, the last two also varying as a. function of the s' tress level.
1The solid curve in Fig.1.2 represents increase in tensile strength with time.
Ideally, when the two curves intersect, the crack occurs.
w r
- 1. 3 Even if the events are limited to the simple one-dimensional environment considered here, it may be inferred from the figure that exactly when the crack would form would be very difficult to predict because of the typical scatter-band widths of the two tLae functions in Fig. 1.lc.
It should also be noted that, depending on the relative humidity and temperature on the free boundary, dimensional changes caused by shrinkage and ther=al effects may reverse.
It is a statistically established truth that hardened concrete is likely to contain cracks especially at planes not having sustained compressive stress. The mechanism described in reference to Fig. 1.1 simply. rationalizes in one dimension how cracking can occur without the necessity of stress generated by load or imposed deformation.
Relationship Between Crack Width and Reinforcement Stress General concepts used to relate crack width to steel stress in terms of propertiec of the concrete section refer to the simplified model in Fig. 1.3:
a concrete prism cast around a reinforcing bar.
It is assumed that the crack occurs in mature concrete and as a result of tensile stress in the embedded bar.
If a sufficiently large tensile force is applied at both ends of the bar, the prism will crack ideally at equal intervals. The interval (crack spacing) is denoted by the notation t.
e The width of the crack at steel surface can then be calculated using the usual definition of strain.
~
o w
v
1.' 4
,= [
(c,, - ccx) dx w
t (1)
C w
= crack width o
c,, = steel strain at point x c
= concrete strain at point x If c, is large compared with ccx, the variation of c may be cx neglected which also suggests that the crack width might as well be considered at the surface of the concrete, a more convenient location for measuring crack width. If the variation of steel stress over 1 is small, the elongation may be written directly in terms of c,,, the mean steel strain without introducing intolerable error.
w
=c t
o sm C (2)
As it would be expected, there is no controversy about the use of Eq. 2.
However, there are differert plausible approaches to organizing the variables in order to obtain the crack interval 1.
C One of the popular approaches to determining i from experimental data is very simple.
In essence, it is patterned af ter the problem of stress trajectories in a " semi-infinite" solid subj ected to a I
concentrated load on its boundary.
Consider the concrete cube in Fig.1.4 with concentrated colinear
~
. tensile forces applied.at.both ends of a central steel bar fully bonded to the concrete.
The distance from the. loaded boundary at which there l
l l
V
)
1.5 will be a surface crack depends on the dispersion race of the stresses within the cube. From this' idealization, the important variable determining crack spacing is seen to be the concrete cover, c.
- Thus, in evaluating experimental data, the basic equation may be set up as i
=ac (3) c a = constant to be determined experimentally Another approach to the interpretation of crack-interval observations is illustrated in Fig. 1.5.
Figure 1.Sa describes idealized conditions inmediately before cracking.
Bond between steel and concrete transfers the tensile force at a varying rate from the reinforcing bar to the concrete. At a point where the tensile strength of the concrete section is exceeded, the crack occurs.
For the hypothetical example considered, this point has been selected to be at the middle of the prism length.
Figure 1.5b shows ideally the stress conditions after development of the first crack. According to the assumptions made, development of other cracks depends on whether bond is sufficient to transfer the force necessary to crack the section in approximately half the length available for transfer.
For a dumber, m, of bars of equal diameter, d,
nditi ns leading b
to cracking according to this hypothesis may be expressed symbolically as'.shown below.
Tensile force transferred to concrete by bond over a length Ec" tensile force necessary to crack concrete section.
i l
I 1
1.6
- [ /2)
.m w d u dx = A f*
(4)
(Ec where m = number of bars
-d
= bar diameter u = bond stress A = area of concrete section f = tensile strength of Concrete Introducing the definition of reinforcement ratio as mwd b 4A e and assuming that bond stress is uniformly distributed along the length of the bar, d
f*
t (5) e o
2u Assuming further that f and u vary similarly with concrete strength, the following equation may be used to evaluate observation of 2.
d i,.gh
( 6) '
c p
1
- 1. 7 Recognizing that the experimental constants a and 8 are dominant and that both mechanisms described may aff ect the physical phenomenon, Eq. 3 and 6 may be combined 1
i
=ae+8 (7) c o
with the understanding that a and 8 are evaluated for the combined ferm.
Application of Predictor Expressions for Crack Width To demonstrate the physical significance of predictor expressions for crack width, it is instructive to apply th.am to a case for which crack-width data are available.
Crack widths measured in the central constant-flexure span of a girder (G141) measuring 14.75
- 28-in. deep in section and spanning 30 f t were reported in Reference 1.1 The dimensions of the girder which was reinforced in tension with three Grade 60 No. 14 bars are shown in Fig. 1.6.
Side cover for the reinforcement was 2-1/4 in.
Measured crack width distributions at various steel stresses f rom 10 to 42 ksi are illustrated in Fig. 1.7.
Widths shown are those measured at the level of the reinforcement on the sides of girder C141.
It is to be noted that the number of cracks incre'ased with steel stress as did the difference between minimum and maximum values. These are typical characteristics of crack-width distributions. They emphasize that a reference to or predic' ion of a crack width for a given structural t
element should never be treated as, say, a beam-depth measurement but always as an index to a distribution of measurements.
,---,-,-r-.v.
1.8 The arrows in the figure indicate magnitudes of the sum (mean
_plus two standard deviations).
It is seen that this sum agreed quite consistently with the maximum width measured at each stress level.
A predictor expression based on the approach described by Eq. 3 is the one used in Reference 1.1.
It is reproduced below as Eq. 8.
cf 8 (8) w =
r 5
, = reference crack width, defined as the sum of the mean w
crack width plus two standard deviations (effectively the maximum crack width), in 0.001 in.
c = concrete cover in in.
f, = steel stress in kai Applying it to girder G141 with f, = 14.0 kai and c = 2.25 in.,
-3 w = (2.25
- 31)/5 = 14
- 10 in.
r The European Concrete Committee (1.2) uses a predictor equation based on Eq. 7.
It is reproduced below in its original units.
16 db (9) w = (1.5 e +
o, ) f
- 10 m
s w = maximum crack width, in cm c = concrete cover in cm d = bar diameter in cm b
C
- 1. 9 o, = percentage of reinforcement in the " tributary" area (area of concrete having its centroid coinciding with the centroid of the steel area) f, = steel stress in newtons /cm Using Eq. 9 for G141, it is first necessary-to evaluate o, in percent:
o, = [(3
- 2.25)/(6.2
- 14.75)]
- 100
= 7.4%
Substituting the relevant data in Eq. 9 for f, = 31 ksi = 21000 2
N/cm,
c = 2.54
- 2.25 = 5.7 cm d = 4.3 cm b
= [(1.5
- 5.7) + (16
- 4.3/714)]
- 21000 wm
= 0.038 cm
~
= 15
- 10 in.
Equations 8 and 9, based on dif ferent behavioral models give comparable results for the case considered. Considering that ene two predictor expressions have been calibrated to approximately similar populations of data, it is not surprising that they lead to similar estimates of crack
~ width.
It is'also noteworthy that both overestimate the measured crack" width. There are two main reasons for the overestimate.
Both expressions ol
1510 were calibrated to ignore the variation of steel strain between cracks.
(Steel strain is assumed to be constant even though it reaches a lower value between cracks.) Expressions derived for general application tend
~' to be conservative even in relation to the observed extremes and are likely to overestimate crack widths by varying margins in most cases.
The important feature of these predictor expressions is that, despite their differences, they emphasize that the quantitative relationship between maximum crack width and steel stress is not constant and that it depends on other variables.
G 4
9 S
9 W
1.11 i
REFERENCES d>
1.1.
M. A. Sozen and W. L. Gamble, " Strength and Cracking Characteristics of Beans with No. 14 and No. 18 Bars," ACI Journal, December 1969, pp. 949-956.
4
~
1.2.
Comite Europeen du Beton, " International Reconsnendations for the Design and Construction of Concrete Structures," Information Bulletin No. 72, June 1970, p. 46.
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Unit Stress Change of Strength i
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Crack Occurs
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Local Tensile Stress i
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Time 1
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Fig.l.2 Variation of Concrete Strength and Internal Tensile Stress with Time i
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f Steel N
5 Stress (o)
________J
~
gTensile Strength of Concrete Concrete Stress
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4 Steel N
N Stress 3
(b) l Fig.1.5 Tensile Stress Distributions t
1
,w w
-,,-----.----e,e.,,
,--m-,
,,,,----,--,,-,..,-.-e.,--a.,,--,-----
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l' 9' (274.3 cm) 12' (365.8 cm) 9'
' l'_
(30.S cm) f rain Measurement Levels St (2.5 cm) 1"
( 7.6 c m) 3" I
(10.2 cm ) 4" D
En 28.0" IIII**I G l4I i
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m Crack Measurement 1
W Locotions l
- 14.75" M i
(37.5 cm) i Fig.1.6 Test Girder C141 i
l i
8
l 10 -
c Steel f
Stress
[
5-4 ksi O
I 5
10 15
{
10 -
f 5-c 31 ksi 0
5 1
5 10 15 E.
2
[
10 -
Z 5-
/
7 4 -
21 ksi O
I 5
10 15 10 -
( Mean + 2 Std. Dev.)
5-7 10 ksi O
~-
1 5
10 15 Crack Width x 1000, in.
Fig.l.7 Measured Crack-Uldth Distribution in Girder G141 at Reinforcement Level
..-.,,w-,
n...
ATTACHMENT 2 EFFECT OF EXISTING CRACKS ON STRENGTH OF REINFORCED CONCRETE MEMBERS-Summary Do existing cracks affect the strength of a' reinforced concrete structure? Attachment 2 was prepared to provide information in answer to this question.
f Referring specifically to the size and type of cracks in the Diesel Generator Building, the concern is whether such cracks would reduce the strength of the structure below the '.evel of nominal strength assumed in design methods.
Examples of basic internal-resistance mechanisms are' considered individually. Cracking in surrounding concrete certainly does not affect the strength of the reinforcement in tension. Test results from Richart and Brown (2.1) and Vecchio (2.4) are invoked to demonstrate that strengths in compression and shear are also insensitive to existing cracks.
s Bending resistance may be considered as being made up of flanges working in essentially axial compression and tension. Evidence from the Richart and Brown (2.1) tests would suffice to conclude that flexural strength would be insensitive to existing cracks.
Behavior of a beam subjected to cyclic loading (2.2) is shown to be consistent with this conclusion.
Cyclic loading data from a test of a box-like specimen with wall's similar to the Diesel Generator Building are also discussed with the same
~ -
y
- 2. 2 conclusion: -existing' cracks o'f the type' observed in the Diesel-Generator Building would not reduce the strength of the bu'il' ding below, that assumed in its original design.
It is concluded.that overwhelming evidence exists from laboratory experiments.and experience with actual buildings to demonstrate that "precracks" of the type considered do not affect significantly the strength of a concrete structure'which has been properly reinforced for the design load combinations.
Introduction Reinforced concrete structures are often cracked before application of a load for which the structure has been proportioned. This note has been prepared to discuss the influence of such "precracks" on structural strength and behavior. Widths of cracks envisioned are assumed to be typically less than one quarter of an inch and never of a size that can lead to instability of a compressed reinforcing bar crossing the crack.
Initially strength of precracked reinforced concrete members subjected to four simple loading conditions are considered:
(1) axial tension, (2) axial compression, (3) bending, and (4) shear. Discussions of behavior under these four " pure" loading conditions are followed by a description of the behavior of a box-like reinforced concrete specimen subjected to cyclic lateral loading.
Axial Tension The condition of axial tension is considered not because it requires discussion but because it represents a fundamental case of loading and O
- 2. 3 because it helps illustrate directly the basic premise of design in reinforced concrete.
l A hypothetical case of a single reinforcing bar embedded along the l
longitudinal axis of a prism of concrete is considered in Fig. 2.1.
l Application of an axial tension on the bar will eventually cause cracking of the concrete at a number of sections as shown.
The basic premise of design in reinforced concrete is that all normal tensile forces are resisted entirely by reinforcement.
If the element in Fig. 2.1 had been designed to carry a certain axial tensile j
force, all the force would have been assigned to the reinforcement.
l l
Consequently, whether these cracks form as the tensile force is applied or whether they had occurred earlier as a result of vol'ume-change or stress effects is of no consequence to the proper functioning of this structural element. Cracking of the concrete would affect only the initial slope of the force-extension relationship.
Axial Compression It is of interest to consider the strength of the same prism (with existing cracks) subjected to axial compression as shown ideally in Fig. 2.2.
The prism is assumed ca be loaded axially through stiff bearing plates so that the overall deformations in the concrete and the steel are the same.
Given that the existing cracks are not so wide as to lead to local instability of the bars or overall instability of the entire element.
it can be inferred from a knowledge of the stress-strain properties of I
,1 L_ _
1
- 2. 4 i
the materials involved that the reinforcement at the cracks will eventually be strained sufficiently to close the cracks. After that event, large compressive stresses will be developed in the concrete leading typically to failure initiated by spalling of t e concrete. Whether this S
" reseating" process affects the strength of the concrete or of the reinforced concrete section can best be determined by experiment.
Several series of tests of reinforced concrete columns were reported by Richart and Brown (2.1) in :he course of an experimental study which was to lead to the fundamental principles of reinforced concrete column design used today. One of these deries, Series 3, was dedicated to the investigation of the effect of sustained loading on column strength. A group of tied and spirally reinforced columns, 5 ft long by 8-in. round (Fig. 2.3), were subjected to a sustained service load for approximately one year. A parallel group of columns were stored for the same period without any load. Changes in steel stress, calculated from measured strains, observed for the loaded and unloaded columns are illustrated in Fig. 2.4 The accumulated strain at the end of the observation period was approximately 0.008 in the loaded columns.
"because of the arrangement of the time-loading rigs, it was necessary to release the loads and to remove the columns from the rigs before placing them in the testing machine. This release of load permitted a recovery of the large elastic strains in the steel and resulted in the formation of tension cracks in the concrete, generally 10 to 12 in apart. The columns were tested at once, and strain measurements showed that when the applied load had reached the value of the one-year sustained load, the cracks had closed, and the steel and concrete strains corresponded. closely with those measured under the spring (previous sustained] loading."
B e
fiS t
yt 4
, * ~. w-
](--
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+.
AA, cu
-&{,
- f.
- 2. 5 l
t Richart and' Brown did~not report crack widths. The widths may be
+
.-+
s.
Jg 4
s Ll3 inferred to be_approximately 0.01 in. from the strains indicated in 3
, w s
Fig.l2.4iand the reported crack spacing. No cracks were observed in the "C N colbans without'. load.'
. Measured) strengths of the columns with and without sustained loading
~
are compared th Table.2.1 reproduced directly from Reference 2.1.
The
.w-last cold $n in the table indicates the ratios of the' observed strengths N
of columns with~ sustained load (which had cracks) P t the observed T
strengths of comparable columns which had not been previously loaded (and which did not have cracks) P. The ratio is observed to vary from N
0.86 to 1.15 with anioverall mean value of 1.0 with a coefficient of variationof6.2per2ent. Richart and Brown concluded'that, a a,ains t the
~'
t background of expected scatter in such test data, there was no significant s
. difference between the strengths of the two groups of columns.
~
Bending A simple and practical model to understand the flexural strength mechani'sm'of a reinforced concrete section is provided by analogy to a
~
structural steel wide-flange section with a thin web.
Resisting moment is generated by a coupie formed by tensile and compressive forces in the 3, '-'
" flanges" of the section as shown schematically in Fig. 2.5.
The censile s -
'e force is provided by.che steel and the compressive force by a concrete-
~
steel composite, quite similar to the idealized element in Fig. 2.2.
From'this interpretation of the flexural-s'trength mechanism and the' 3
information supplied above, it follows that existence of cracks
-e
+
t n
perpendicular to the bars, whatever the cause, would not reduce the flexural strength of the section'.
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s?
~. -
s 6
7 y
b
-,,y r
.m
2.6 The same conclusion may be reached by recognizing that the flexural strength of' reinforced concrete sections reinforced in tension only with typical amounts of reinforcement is insensitive to changes in concrete strength.
Influence of the concrete strength on flexural capacity is even less if the section has compression reinforcement. Thus, any reduction in compressive strength because of local spalling during the reseating of the crack is likely to have negligible effect on flexural strength.
A common experimental demonstration of the trends discussed above is provided by response of reinforced concrete beams to load reversals.
Consider the measured relationship between force and mid-span deflection of a test beam reported in Reference 2.2.
The first loading to over 10 kips would cause a pattern of cracks as shown ideally in Fig. 2.7d.
Return to zero load would leave a " residual" crack pattern as shown in Fig. 2.7e.
Clearly, the concrete to work in compression when the load is increased in the opposite direction is cracked at zero load.
But it is seen in Fig. 2.6 that the cracks do not prevent the beam from developing its strength in the opposite direction.
Shear Vecchio (2.4) reported a series of 30 tests to investigate the force-deformation properties of reinforced concrete laminae subjected to h-plane forces. The results of this investigation' permit a comparison of the strength of reinforced concrete laminae which have been cracked i
~\\
j
5-2.7 before shear loading with the strengths of laminae which had no visible cracks before loading.
(The term " lamina" is used here for a slab to avoid association with " slab shear strength" which refers typically to out-of-plane forces.)
To approximate the conditions of a " pure" shear loading, Vecchio used the mechanism shown in Fig. 2.8 to apply reasonably uniform shear forces along the edges of a reinforced concrete lamina (Fig. 2.9) measuring 35
- 35
- 2-3/4 in.
Reinforcement was provided by two layers of annealed welded wire fabric mats.
Twelve specimens, with properties listed in Table 2.2, failed in shear under " shear loading" before reinforcement in both directions had yielded. Of this group, only ten with concrete strength in the range 2300 to 3100 psi are considered here in order to be able to discuss the results directly, without normalizing the data to account for changes in concrete strength.
Measured unit shear strengths of the specimens loaded monotonically to failure are plotted using open circles against the product a f in Fig. 2.10.
(The term o refers to the lower of the reinforcement ratios g
in the two orthogonal directions.)
One specimen, PV 26, was cracked in biaxial tension before loading in shear. The cracks were obtained by applying forces equal to 60 percent of the calculated yield stress of the reinforcement simultaneously in each direction (of the reinforcement parallel t.o the edges of the specimen). Shear forces were applied after release of the tensile forces.
As represented in Fig. 2.10 by a solid circle, this specimen developed a strength comparable to that of the monotonically loaded specimens.
4
+,
- 2. 8 Another spectmen,.PV 30, was also initially cracked in biaxial tension in the same manner as PV 26 was cracked. However, PV 30 was increased in 100-psi increments starting from 125 psi. At each stress level, the stress was cycled ten times. The maximum shear stress developed by PV 30 is also shown by a solid circle in Fig. 2.10.
It is evident that the strength of PV 30 was not perceptibly affected by
. existence of initial cracks and by the stress reversals.
The observed results can be anticipated by interpreting the response of the lamina in terms of the simple " truss mechanism" illustrated in Fig. 2.11.
The diagonal truss elements operate in a manner similar to the tension and compression elements shown in Fig. 2.1 and 2.2.
The stiffness of the lamina would be expected to decrease because of cracks existing before load application, and it does. But given that the "precracks" do not affect strength in cases illustrated in Fig. 2.1 and 2.2, it follows that precracks would not change strength significantly in the case of a lamina subjected to shear forces.
Behavior Under Cyclic Loading of a Reinforced Concrete " Box" The observed behavior of a stubby box-like reinforced concrete structure subjected to lateral-load reversals at the structural engineer-ing laboratory of the University of Tokyo (2.5) is of interest for two (a) the specimen is a low-rise (stubby) reinforced concrete reasons:
box with uniformly reinforced walls similar to the Diesel Generator Building and (b) the loading conditions in its walls combine the types of loadings considered individually in the preceding sections.
3-
-,n.-
_._.,~c.
y 2.9 Plan and. elevation of the specimen considered (B6) is shown in Fig. 2.12 which also describes the test rig.
Plan dimensions, out-to-out of walls, of the specimen were 0.83
- 0.83 m (approx. 2.7 ft). ' Wall thickness was 0.08 m (approx. 3 in.).
Lateral loads were applied at a
level 0.8 m (approx. 2.6 ft) above the top of the base slab.
Concrete strength was reported to be 256 kg/cm (3600 psi) at time of test.
As shown in Fig. 2.13 walls were reinforced with 6-mm bars (corresponding approx to No. 2 bars). Vertical and horizontal bars were spaced at 13.2 cm, except near the corners, resulting in a reinforce-ment ratio of 0.5 percent in the wall sections away from the corners.
Yield stress of the reinforcement was 3910 kg/cm (56 ksi).
Umemura, et al, calculated the maximum value of the applied lateral load to be 34.3 tons (75.7 kips) corresponding to the development of the calculated flexural capacity. The curve identified by the legend "e-function method" shows the calculated response of the specimen for
- monotonically increasing lateral load.
The lateral load was applied alternately in opposite directions using the arrangement of hydraulic jacks shown in Fig. 2.12.
The loading history is documented in Fig. 2.14 Specimen B6 was loaded initially to 30 tons (66 kips). The load was then reduced to zero. At that time the walls parallel to the axes of the jacks would have been cracked as shown ideally by the sketch in the figure. The specimen may then be considered as one having "precracks" because the existing cracks were caused by a loading direction radically different from the one it is to sustain. As the load is applied in the y n
,r.,-.-_-
--cw,-
,s,,,,--r gr v -w
-y 9-vr
+-
e v-
2.10 reverse direction (negative values of load in Fig. 2.14), compressive stresses act on the crack planes while tensile stresses develop parallel to the crack planes. But the-strength of the specimen is not reduced.
' '.This observation can be rationalized on the basis of the loading conditions described earlier. Flexural-strength is developed primarily by forces
.on the " flange" walls which are subjected essentially to alternating axial and tensile forces.
It was discussed that there should be no
' critical decay in axial compressive strength of the flange walls under the loading conditions considered.
It can also be inferred from Vecchio's test results (2.4) that the " web" walls carrying the shear would not be affected critically by the existence of "precracks" at the beginning of loading in each direction in each cycle.
Final states of cracks in the web and flange walls are illustrated in Fig. 2.15.
Concluding Discussion Internal resistance mechanisms in reinforced concrete members may be described by combinations of three simple conditions:
axial compression.
axial tension, and shear.
In fact, the last condition has to be treated independently only because the principal stress directions corresponding to the shear stress are not usually colinear with the directions of reinforcement.
It has been shown, by example where necessary, that existing cracks do not affect significantly the strength in tension, co'pression, and m
shear of properly reinforced concret*c elements.
d i
2.11 Overwhelming evidence from the field and fro:n the laboratory indicates that reinforced cor. crete structures will develop their design strength even if they do have "precracks", provided the structure has been proportioned and detailed to resist the design load combinations.
The examples discussed rationalize the experience.
e i
e 9
e 9
9 e
- n-~r-
--m,-
w--
y e
y 4
-w--.---
,----gy 9-,,-
2.12 REFERENCES 2.1 F. E. Richart and R. L. Brown, "An Investigation of Reinforced Concrete Columns," Bulletin No. 267, University of Illinois Engineering Experiment Station, June 1934, pp. 48-54 2.2 J. A. Blume, W. M. Newmark, and L. H. Corning, " Design of Multi Story Reinforced Concrete Buildings for Earthquake Motions,"
Portland Cement Association, Skokie, 1961, p. 130.
2.3 M. A. Sozen, " Hysteresis in Structural Elements," Applied Mechanics in Earthquake Engineering, ASME Proc. of Winter Annual Meeting, 1974, pp. 63-98.
2.4 F. Vecchio, "The Response of Reinforced Concrete to In-Plane Shear and Normal Stresses," Ph.D. Thesis submitted to the School of Graduate Studies, University of Toronto, December 1981, 332 pp.
2.5 H. Umemura, H. Aoyama, and H. Noguchi, " Experimental Studies on Concrete Members," Faculty of Eng., Dept. of Architecture, University of Tokyo, December 1977, pp. 32-48.
A I
6 O
O
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m.
+,,.,r--
s
- ----------.--+.-y--.m-
- - - --, -, - - -yr -
c TABLE 2.1 (Reproduced from Reference 2.1)
SrnaxOru or Col.cune or Smarts 3 Arian Oxs YEAR UNDER SestAixso IAAntNo Eneh value ropeseente the test resules fresa two solemas. Colume asetaan. 30.2 for aperal eulurans.
33.4 fee ned solumns.
Nesnimal Deussa Columna Afase One Year Columna Aftee One Yeme Under russassed Landene Under.No Loadnas Pereentase
/.,
of itmeaforos.
L*ltammae lead, fr L34smate land, fs bt88 Ib. pee eneas ps/Pr 4'
versica! l spiral th-lb.pae I,b,. per an. sa.
Ib.
I.annaaTome Are Stemmes 2000 1.3 2
234 nin 7483 3 244 fa) 4 sAS 0 07 4
0 237 11:59 44.13 244 !ssa 4 //a4 1.04 4
2 3Ji f4n AAS/.
Jrl fort a 440 0.93 6
2 343 aliO 7030 344 fllu 7 073 1.08 3J00 3.3 0
225 an0 422n 4
0 3rJ Gul samt 3r10 **
4 Ski
- 0. 7) 4 2
4srs laut sea.us 394 ULM 7 MO U.v4 4
0 JI4 enn tema 6
8.2
.'864 800 7323
- in00 1.3 2
Im3 2fM 76AS 304 runs 7 40 8,og 4
0
- leo 7fWl 6915 485 ene 7 763 1.32 4
2
.9st gras ipes) 454 ldag 3 ann o.g7 4
2 41PD 70ft U9484 353 Te10 [ 10 fMiG 1.01 Aversee j l.08 Slotse 2tTna4esa f 222 ruus 2000 4
0 48?.
I'JO 'sen h
3 370 i
1.2 0M s
277 '.ul 4415 Jim less a a J4o n.wT 4
2 341 Jist Ngn J2.1 was l a 440 8.ul Jfat 4
0 268 fees 4wa J02 IDus p a n,%e 1.85 4
1.2 454 asse en64
- 427 tesi
) n ;esa
- o. ru 4
2 581 J A) 79.N) irJ6 TdM
{
7 >*Jt)
U. !/W A
SUUG 4
{
O' 358.*nt j tt373
.fla samt 3 AOS O. t 4J 4
8.2
- 4Altaas l 4t's esag 4 ALS
, it 47 4.88 dent blami 4
2 18410 4=J. ins, '
9 503 1.tM Averase,
p.us Grand Average Value of Itatte P./Pr i 3.eA)
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10 TABLE 2. 2 Properties and Test _Results of Laminae Subjected to Shear and Failing before Yielding of Longitudinal Reinforcement Reinforcement Long.
Transv.
Shear Stress l
- c u
g g
Mark psi y
y psi PV 9 1680 1.79-66.0 1.79 66.0 542 PV 10 2100 1.79 40.0 1.79 40.0 575 PV 12 2320 1.79 68.0
.45 39.0 454 PV 13 2640 1.79 36.0 0
0 292 PV 18 2830 1.79 62.5
.32 59.7 440 PV 19 2760 1.79 66.4
.71 43.4 573 PV 20 2840 1.79 66.7
.89 43.1 617 PV 21 2830 1.79 66.4 1.30 43.8 729 PV 22 2840 1.79 66.4 1.52 60.9 880 PV 26 3090 1.79 66.1 1.01 67.1 784 PV 27 2970 1.79 64.1 1.79 64.1 920 PV 30 2770 1.79 63.3 1.01 68.4 744 Note: Data from Reference 2.4 2
g e
--e w,-
-,,,w,.-----,w
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,-. ~, - -- ~ -- - - - - +
I 2.1 Reinforced Concrete Element Resisting Axial Tension Very Stiff Bearing Plate
~
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- .: y
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' Denixo.5csvia.s to buoixo 2.4 Stress Redistribution in Columns (Richart and Brown, 2.1) 9 G
Concrete Stress
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2.10 Variation of Measured Shear Strength (2.4) i 4
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" Diagonal" Truss Elements) 1 2.11 Idealized Mechanism for Resistance Mechanism of a Lamina Subjected to She.ar Stress 1
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Im in ee 2.13 Dimensions and Reinforcement for Test Structure B6 O
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Fig 2.1 Load-Deflection Curves 7
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4, C ress.4rea 2.14 Load-Displacement History for Test Structure B6 6
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.i 2.15 Crack Patterns for Test Structure B6 i
ATTACIDENT 3 CRACKS IN CONCRETE UALLS Reprint of an article by Ake Holmberg and Sten Lindgren S
O
Cracks in concrete walls Nati:nal Swedish Building Research umma es Ake Holmberg & Sten Lindgren D7:1972 A a earlier investigation. " Crack Spacing be unreliable. All the data that were now Key words:
and Crack Widths Due to Normal avadable have been analysed agam. and crack spactng. crack width. concrete force or Bending Moment"(Document this analysis resulted m a new formula.
walls, rigidity. imposed deformauons D211970). published by the same which is similar in principle to that de.
authors, has led to fundamental con-duced by Efsen and Krenchel. This new clusions regarding the distrrbution and formula involves a slightly higher cottTs.
the width of stable cracks in concrete cient of variation than tne previous for.
structures. The arailable data on crack mula in its range, but covers the totality spacings was summarized m a crack of the test results under consideratson.
formula The present report however, The new formula was furthermore veri.
rejects thisformula and presents a new lied by applying it to extensive results one which takes into account the full obtained by Nawy. et al. from tests on range of experimental material avail.
two.way slabs. This venlication indicat.
able, including material contained in ed that the formula in question might this report. The new crackformula has also be applicable to judscious predsc.
a wider range of applicatson. covering tion of crack widths in such slabs.
as it does walls havung different types The new formula is of reinforcement and also to a certain extent slabs wtth two.way reirtforcement s,., = 0.0$$ + 0.1 as,,*
The present investigation was made on O3 the walls shown in FIG. l. which were where 0.2 m in thickness. The undisturbed area of observation on each face of the wal!
- e. =
the Gnal fsmaHat) mean crack was 1 x 3 m. Apart from a single excep.
spacing, m metres, reached at tion. this investigation confirmed the high values of the stress, a,.
earlier observations. The walls were in the remforcement m a crack strained in the test set up shownin FIO.2.
p the diameter of a reinforcing They were restrained so as to remam bar plane in the cases where the tensde force the diameter of that remforcing was eccentric. The mean strain over a t
bar in a group which has the length of 3 m was increased in steps'.
and was maintained constant at the re smallest concrete cover' and specuve values. viz 0.125 per md. 0.2 P'
per mil. 0.35 per mil. 0.65 per mil. and d minant effect on crack form.
l 1.25 per md. The time interval between ation two consecutive steps was I day, but the A,
that maximum portion of the Document 07:1972 has been supported last interval was almost 2 days.
gross cross. sectional area of the by Grant C 599 from the Swedish As the field of application was extend.
concrete whose centre of grav.
Council for Building Research to Cen-ed, the previous formula for the calcu.
ity coincides with that of the teridf &.Holmberg.1.td Consultmg lauon of the crack spacmg was found to reinforcement En gmeers. Lund. Sweder.,
==
=
4 i
UDC 69.022.e91.32 t- -
624.044
,t 69.059.2 Srn A 7
.4
(:1),(::)
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ISBN 91-340-2027-1
.1 Summary of:
-.e u.
-, e,
.e Holmberg. A & Lindgren. 5.1972.
M C/acks in concrete isolls. (Statens insti.
as.'"
- m..m
- e..e m.
- e. e a.
.n e
n
- e..=
tut fue byggnadsforskning) Stockholm.
Document D7:1972. 70 p.. dl. IS m
e-r S w, g,*
1lI:
7 1 f rw. 1M 10 19 1}
o7 f t 1A
- g. g t i.,'.
i.
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t *.t-
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$**(
The document is in English with Swed.
i
I ish and English summanes, iW &c
.g.
4 4.. 43 4 ;;
l,',j L ;,: ad
'd 4c.
i-w e
e a
e e
e e
.ea...a.
FIC. l. Watts sub rered to the tests. includsng ss' alls Nos. Il to 16, whrch mere used for Dsstribution:
t shrmange measurements. The eenee posses on the renerrte un the end surfisces of the lat.
Svensk Dngtssnst ter mults are murard w. Att Jimenssons ure nommuk Jamensions in mas Q.') Ks4U.
Dos 1403. S~ lIL 84 Stockholm Type Kum swel rebed bu. l3 mm in diumerer. peat stress of reenfureement ubt 400 stNim3 Sweden r
$s?!s.o 1.spe Pl.,on, rwnJ sessi.su,.et.*ny st.% r.,a p.14 ser,n ysk).. ns.e pervem a,eset r
b r.
h.*tAl st.% m; ps:J roress
C c cracn.
n The final crack width approaches as s
a limit the crack spaans miniciplied
{
q by c, = a/E,. where E, is the modie.
l $
lus of elasocity of the reinforcement.
O O
i This statement holds good even if the 4
i 7 action has not led to the final crack J
.. - --- ---- g
/
spacmg. The vanation in the crack width in a vertical direcnon, at right
-.gW- --
ag W
u angles to the reinforcement, is consid-ered to be a short-time edect.
The coefficient of variation in s,.. is 0.2. and hence a reasonable maximum value is I.4 times the calculated value of 8,..
s -........
__..,=@'
The maximum crack width m. walls.
etc., which are sufficiently long to
C contain the crack havmg a manimum width is about I.7 times the calculat.
ed value of the crack width, and, for the magmfication factor 1.7. the coef.
ficient of vanation is about 0.25.
If 1 wall is reinforced at one face FIG. <1. Machine saedfor the tensson tests on the walls, wnth controlled elongatson.
only, and if A, is smaller than the total cross sectional area of the wall.
then the crack formation on the face
- e e e.........
that is adjacent to the reinforcement
~~N
~'"
will be in accordance with the above-iiiiii. i a i+
.c irii i i a mentioned formula. On the other
~
hand. if the eccentricity of the reinforce.
5 N
a ment is great, then the erack devel-
- -._l d
opment on the opposite face of the I '''''''' ' '
I wall rnay be considered to be entirely uncontrolled. With a slight exaggera-
- L a.
1 tion, such a wall may be regarded as a reinforced wall that is conuguous to a non-reinforced wall. see FIG. 3.
_ ' A The formula for the calculation of the
_, _,,,,, P " " 8 f e ! 1 PS -*' * *""' p.pZ t _J crack spacing and the above state-g ; '-
m i
N,.
ment involve by implicauon certain
,,,.jy,y
.,)
,,,, 33, i.,
practical recommendations for design.
t %
- e ^% wa # -
^
^t q.s
..a,i
!i p. i < e i The rigidity of the wall varies in
--~
.E such a way that it undergoes abrupt 4 s,,,,
e, changes within extreme limits which are determined by the untracked con.
FIG..l. Cracks be wall der completson of test.
crete and by the bare remforcement in the crack, respectively. The present
/,.
investigauon alTords a basis for esti.
mating the actual limits of the rigidity K a at a defined stress.
FIG. 4 shows in terms of numencal J
values the decrease in the rigidity with increase in the mean strain. C
?,=0005 expressed by the factor ar in the re-2 e
lation l
l a,. E,Cs, S* 00(*
I where g
y gg g
a, the stress in the reinforcement s en in a crack.
G o E,
the modulus of elasticity of the tesnforcement.
M. 4. Rel.onen berwun en und E,CJer, Lonnie nehses et #s = MJ und M/J, C.
the mean stram of the wall, deep I
beam, stab.etc
"'#"""M a,
the stress in the reinforcement at the instant of appearance of the first crack.
As may be seen from FIG. 4. the effect of the ratio of reinforcement g on the ngsdity is slight. On the other hand. the elTect of the tensale strength of the concrete. which is in itself dilii.
cult to determme and liable to vary.
is by no means slaght. If a system is
)
highly staucally mdetermmate, then the design probicm is to a certain es.
tent transferred from stauca to statantics.
o t'rdes te r si trest ese rt'i' r 6.ie ev.*etw in.enes. s.w
- ~ - -
r i
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l-ATTACEMENT 4 l
i EVALUATION OF CRACRING IN DIESEL GENERATOR i
BUILDING AT MIDLAND PLANT I
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,,,,,,,_,,.._,y,,.m,m._
.,,,___.,_, _. _,,..,, ~ ~,,_r,,,_m._.
..r.,,,_,,,,,,-..,.-....-m.#,,_.
TABLE OF CONTENTS Faqe INTRODUCTION.
4.1 DESCRIPTICN OF STRUCTURE.
4.1 EVALUATION OF CRACKING.
4.11 Bechtel Crack Mapping.
4.14 CTL Observations.
4.27 RECOMMENDED PROGRAM FOR MONITORING STRUCTURAL INTEGRITY.
4.30 Displacement Monitoring 4.30 Crack Monitoring.
4.33
SUMMARY
AND CONCLUSIONS 4.34 a
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conetruction technology laboratortee O
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EVALUATION OF CRACKING IN DIESEL GENERATOR BUILDING AT MIDLAND PLANT by W. G. Corley~and A. E. Florato*
s INTRODUCTION This report presents an evaluation of the significance of cracks observed in the Diesel Generator Building located at Midland Nuclear Power Plant Units 1 and 2.
Observed cracks in this structure are described.
A program for future monitoring of structural integrity is described.
DESCRIPTION OF STRUCTURE A site plan for the Midland Nuclear Power Plant is shown in Fig. 4.1.
The Diesel Generator Building is located directly i
south of the Turbine Building.
The building is a two-story reinforced concrete structure.
It is partitioned into four bays by load-bearing reinforced concrete walls.
Elevations, plans, and sections of the Diesel Generator Building are shown in Figs. 4 2 and 4.3.
Diesel generators housed in the building are used to provide power to attain safe shutdown of the plant in case of a design l
Respectively, Divisional Director, Engineering Develo'pment Division, and Director, Construction Methods Department, t
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basis accident, and to operate the plant in case of power outages.
Because of its safety-related functions, the Diesel Generator Building is designed as a Seismic Category 1 struc-ture.
As such, it must maintain its structural integrity during and after a design basis accident, including a postu-lated safe shutdown earthquake.
As shown in the elevations in Fig. 4.2, overall length of the Diesel Generator Building is 155 ft.
Overall width, excluding external enclosures, is 75 ft-4 in.
The basic layout of walls in the Diesel Generator Building is shown in Fig. 4.4.
Table 4.1 contains details of selected walls designated in Fig. 4.4.
Exterior walls of the structure running in the north-south and east-west directions are 2.5 f t thick.
Primary vertical and horizontal reinforcement in these walls is No. 8 bars at 12 in, on centers a't each face.
Interior walls of the structure run in the north-south direction and are 1.5 ft thick.
These walls contain No. 7 bars at 12 in. on center, each direction at each face.
Specified concrete strength for walls of the Diesel Gener-3 ator Building is 4000 psi.
Grade 60 reinforcement is used in the walls.
i Table 4.2 contains a listing of Bechtel drawings that were used to obtain data on member dimensions, and on amounts and arrangement of reinforcement.
The Diesel, Generator Building was founded on plant fill and constructed between the summer of 1977 and the spring of 1979.
It has been reported that settlement of the Diesel Generator
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TABLE 4.1 - DETAILS OF SELEpTED WALLS IN, DIESEL GENEPATOR BUILDING Wall Primary Primary Wall Thickness, Vertical Horizontal Description ft.
Reinforcement
- Rein forcement
- North Wall 2.5 No. 8 9 12" No. 8 0 12" South Wall **
2.5 No. 8 9 12" No. 8 9 12" West Wall 2.5 No. 8 9 12" No. 8 9 12" West Center Wall 1.5 No. 7 9 12" No. 7 9 12" Center Wall 1.5 No. 7 9 12" No. 7 9 12" East Center Wall 1.5 No. 7 9 12" No. 7 9 12" East Wall 2.5 No. 8 9 12" No. 8 9 12"
- Reinforcement each face
- Reinforcement layout varies because of numerous wall openings.
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TABLE 4.2 - DIESEL GENERATOR BUILDING DRAWINGS
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Bechtel Revision Drawing Date Title go, No.
C-140 14 2/14/81 Prcject Civil Standards.
Rein-forced Concrete General Notes and Details Sheet No. 1 C-1001 12 10/28/81 Concrete Outlines - Plan at El. 634'-6" Sheet No. 1 C-1002 14 10/28/81 Concrete Outlines - Plan at El. 634'-6" Sheet No. 2 C-1003 9
6/26/80 Concrete Outlines - Plan at El. 664'-0" Sheet No. 1 C-1004 10 7/13/81 Concrete Outlines - Plan at El. 664'-0" Sheet No. 2 C-1005 4
1/31/80 Concrete Outlines
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C-1006 3
2/28/79 Concrete Outlines - Roof Plan at El. 680'-0" Sheet No. 2 C-1007 6
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Concrete Outlines - Longitudinal Section C-1008 10 4/22/80 concrete Outlines - Cross Section C-1013 6
3/20/80 Reinforcing Details - Foundation Plan Sheet No. 1 C-1014 3
1/13/78 Reinforcing Details - Foundation Plan Sheet No. 2 C-1015 4
9/26/80 Reinforcing Details - Floor Plan at El. 634'-6" Sheet No. 1 C-1016 5
1/5/81 Reinforcing Details - Floor Plan at El. 634'-6" Sheet No. 2 C-1017 2
8/6/79 Reinforcing. Details - Floor Plan at El. 664'-0" Sheet No. 1 l
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C-1018 2
8/6/79 Reinforcing Details - Floor Plan at El. 664'-0" Sheet No. 2 C-1019 2
9/10/79 Reinforcing Details - Roof Plan at El. 680'-0" Sheet No. 1 C-1020 3
9/10/79 Reinforcing Details - Roof Plan at El. 680'-0" Sheet No. 2 C-1021 4
1/6/78 Reinforcing Details - Wall Elevation Sheet No. 1 C-1022 4
1/6/78 Reinforcing Details - Wall Elevation Sheet No. 2 C-1023 4
1/9/79 Reinforcing Details - Wall Elevation Sheet No. 3 C-1024 4
1/9/79 Reinforcing Details - Wall Elevation Sheet No. 4 C-1025 3
1/6/78 Reinforcing Details - Wall Elevation Sheet No. 5 C-1026 4
3/30/79 Reinforcing Details - Wall Elevation Sheet No. 6 C-1027 4
3/30/79 Reinforcing Details - Wall Elevation Sheet No. 7 C-1028 4
4/25/79 Reinforcing Details - Wall Elevation Sheet No. 8 C-1029 4
4/27/78 Reinforcing Details - Wall Elevation Sheet No. 9 C-1030 2
1/6/78 Reinforcing Details - Sections Sheet No. 1 j
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1/9/78 Reinforcing Details - Sections Sheet No. 2
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TABLE 4.2. - DIESEL GENERATOR BUILDING DRAWINGS (Continued)
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7/21/77 Reinforcing Details - Sections and Details Sheet No. 3 C-1033 0
7/21/77 Reinforcing Details - Sections and Details Sheet No. 4 C-1034 0
7/21/77 Reinforcing Details - Sections and Details Sheet No. 5 C-1035 1
4/27/78 Reinforcing Details - Sections i
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C-1036 4
8/13/80 Reinforcing Details - Sections and Details Sheet No. 7
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Building exceeded the estimated settlement value given in the Midland Plant Final Safety Analysis Report.
It has also been reported that the excessive settlement was caused by plant fill
'having a different compaction from that assumed in design.
Footings of the north-south walls of the Diesel Generator Building are penetrated by electrical duct banks as shown in Figs. 4.5 and 4.6.
It has been reported that when settlement of the buildings occurred, these duct banks were in contact with the footing.
It is postulated that this support restrained vertical movement of the north-south walls.
Contact between the duct banks and footings was eliminated in November 1978 by removing concrete at the duct bank-footing interface as illus-trated in Figure 4.5.
EVALUATION OF CRACKING During construction of the Diesel Generator Building, cracks were observed in the concrete walls.
It has been hypothesized that these cracks are related to two factors.
The first is the normal cracking that can occur from restrained volume changes in reinforced concrete.
The second is cracking that can occur 4
because of dif ferential settlement such as that reported in the I
Diesel Generator Building.
In this report, evaluation of crack-ing is based on crack mapping reported by Bechtel, and on over-all visual observations of the building made by Construction
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Bechtel Crack Mappinq Cracks in walls of the Diesel. Generator Building were mapped by Bechtel personnel at several stages of construction.
. Figures 4.7 through 4.11 show cracks observed in the north-south walls of the Diesel Generator Building between elevations 630 ft-6 in. and 664 ft-0 in.
A key to wall designations is shown in Figure 4.4.
In Figs. 4.7 through 4.11 only cracks with widths of 0.010 in or greater are shown.
Numbers show measured crack widths in thousandths to the nearest five thou-sand th.
The drawings are based on cracks mapped in July 1981.
Maximum reported crack width is 0.020 in.
Cracking in the vicinity of duct banks is particularly evident in the center wall as shown in Fig 4.9.
Cracks observed in north-south walls of the Diesel Generator I
Building between elevations 664 ft-0 in, and 681 ft-6 in, are shown in Figs. 4.12 through 4.16.
These figures are taken from Bechtel drawing SK-C-669.
Cracks shown in this drawing were j
mapped in January 1980.
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Figures 4.17 and 4.18 show cracking observed in the north wall of the Diesel Generator Building.
These figures are taken I
from Bechtel drawing SK-C-659.
The cracks were mapped in February 1980.
Cracks in this wall were remapped by Bechtel personnel in July 1981.
Results of the remapping are shown in Bechtel drawing SK-C-770, Revision A dated February 9, 1982.
Although a few addition'al cracks with widths of 0.010 in. or greater were observed in July 1981, no significant differences in overall crack patterns were noted.
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i Figures 4.19 and 4.20 show cracks mapped in the south wall of the Diesel' Generator Building. These figures were taken from Bechtel drawing Number SK-C-658. Based on _overall review of Bechtel drawings, it appears that many of..the cracks shown are attributed to restrained volume changes that occur in concrete during curing and subse-4 quent drying. However, the patterns observed in several north-south walls of the Diesel Generator Building indicate that cracks could have resulted from differential settlement of the walls between the duct banks and the north and south portions of the structure. It is possible that differential settlement was caused by extra support provided by the duct banks when they came in contact with the wall footings. CTL Observations visual observations of cracking in walls of the Diesel Gen-erator Building were made by CTL personnel on January 12, 1982 and February 9,1982. Construction Technology Laboratories personnel did not do detailed mapping of cracks. CTL inspec-t tions were made to obtain an overall impression of cracking in the structure and to correlate this impression with that obtained from review of Bechtel crack mapping drawings. In general, impr s ie s ons obtained from the visual inspection at the site were consistent with those obtained from review of the Bechtel drawings. Because the observed pattern of cracks in the center north-south wall of the Diesel Generator Building was most indicative j of cracks caused by differential settlement, one face of this -4.27-construction technology laboratories --n ---,-m, -,-,v., ,_,,-w. .n- ,,-,,r,-e,- - - -, - -,,,, -,, -, - .-....,,,---e_,--n_,, .g.--
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wall was remapped by CTL personnel on February 9,1982. Figure 4.21 shows cracks observed in the center wall on the east face. ~ . Maximum measured crack width was 0.025 in. The pattern of cracks at the electrical duct penetration is consistent with a pattern that could occur because of differential settlement about the duct. Development of settlement cracks is discussed by. Dr. M. A. Sozen in the main body of this report. RECOMMENDED PROGRAM FOR MONITORING STRUCTURAL INTEGRITY It-is recommended that future integrity of the Diesel Gen-erator Building be monitored by periodic measurements of dis-placements of the structure and by periodic inspection of cracks. Displacement Monitorinq Displacement measurements should be made periodically to monitor absolute and relative movement of walls of the Diesel Generator Building. _ Figure 4.22 shows approximate locations of recommended displacement measurement points. These measurements will confirm that current estimates of settlement limits are not exceeded and will provide a means to verify structural integrity. Measured displacements should be recorded as a func-tion of time.- The frequency of measurements will be selected in relation to the observed rate of displacement. .It is also. recommended that the time history of displace-ments be submitted.on a regular basis to qualified e'ngineers familiar with reinforced concrete behavior and design. The qualified engineer will provide recommendations on whether wall 4.30-construction technology Isboratories ~ O m.- m.m -22..~.. m ..-,---n
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displacements are of significance with regard to structural integrity of the building. Crack Monitoring As a supplement to the displacement monitoring program, periodic visual inspections of the Diesel Generator Building should be made to determine if new cracking has developed or if existing cracks have changed in width or length. Crack inspections should be conducted by qualified personnel. Because the Diesel Generator Building is not being under-4 pinned, it is not anticipated that the crack monitoring program will be as rigorous as that for the Auxiliary Building. However, as a minimum, the following steps should be included. Initially a crack survey should be made for the entire g structure. This will provide a base for future evaluation of changes in crack patterns or crack widths. All visible cracks should be marked and recorded. Selected cracks should be measured to obtain an estimate of maximum crack widths. If displacement measurements indicate that building settle-t ment. exceeds the predicted values, cracks in the structure should be remapped. Within four weeks after observation of the cracks, an engineer f amiliar with reinforced concrete behavior and design'should provide a t:ritten report that describes significance of o$ served cracks and~ recommendations for main-taining structural integrity of the building. -4,33 construction technology laboratories
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- o, UNITED STATES e#
e NUCLEAR REGULATORY COMMISSION kG N j_L.4 ,g. t WASHINGTON, D. C. 20555 %p**ww*,/ e DEC 2 81981 PRIrCTPAL STAFF Docket Nos.: 50-329/330 OM,' OL D/n clo I A/n
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Mr. J. W. Cook " ?7 - W DE&TI W D NU Vice President Consumers Power Company DEP W" 1945 West Parnall Raod Jackson, Michigan 49201
Dear Mr. Cook:
Subject:
Announcement of Geotechnical Engineers Inc. as WRC Staff Consultant for Underpinning of Auxiliary Building Area and Service Water Pump Structure The NRC Staff's review of the geotechnical engineering aspects of the underpinning of the Auxiliary Building and Service Water Pump Structure for Midland Plant, Units 1 and 2 is being performed with the contractual assistance of: Geotechnical Engineers Inc. ATTN: Dr. Steve J. Poulos 1017 Main Street Winchester, Massachusetts 01890 The principal investigator and Vice President of Geotechnical Engineers Inc., Dr. S. Poulos, is also being assisted by Nr. Reuben Samuels, Vice President of Crintnint Contracting Company in New York. This team adds extensive underpinning expertise to the NRC's geotechnical review of Midland and is in addition to our continuing contract with the U.S. Army ~ Corps of Engineers. The hRC's technical coordinator for this additional contract will also be Hr. Joseph Kane. We request that Geotechnical Engineers Inc. be added to your mailing service list for all technical documents, drawings or other correspondence dealing with the ' nderpinning of the Midland Auxiliary Building, Feedwater Isolation u Yalve Pits, and the Service Water Pump Structure. We understand that Mr. Kane has made verbal requests regarding the transmittal of certain existing documents to Geotechnical Engineers Inc. and plans further discussions with your staff to this end. We believe this addition will provide NRC with the increased expertise and experience needed to review Consumer's pending underpinning submittals 9 v pu p JM a
r ..? Mr. J. L Cook e in a timely and effective manner. Your prompt attention in forwarding information to our consultants is appreciated. Sincerely, MMM S~ Elinor G. Adensam, Chief Licensing Branch #4 Division of Licens,ing cc: See next page ' e e D 9 6 9 e e 9
4 . MIDLAND Mr. J. W. Cook Vice President Consumers Power Cogany 1945 West Parnall Road Jackson. Michigan 49201 cci Michael I. Miller. Esq. Mr. Don van Farrowe. Chief Ronald G. Iamarin. Esq. Division of Radiological Health Alan S. Farnell. Esq. Department of Public Health Isham, Lincoln & Beale P.O. Box 33035 Suite 4200 Lansing. Michigan 48909 1 First National Plaza Chicago. Illinois 60603 William J. Scanlon. Esq. i 2034 Pauline Boulevard James E. Brunner. Esq. Ann Arbor. Michigan 48103 Consumers Power Cog any 212 West Michigan Avenue U.S. Nuclear Regulatory Commission Jackson. Michigan 49201 Resident Inspectors Office Route 7 Myron M. Cherry. Esq. Midland. Michigan 48640 1 IBM Plaza Chicago, Illinois 60611 Ms. Barbara Stamiris 5795 N. River I Ms. Mary Sinclair Freeland. Michigan 48623 1 5711 Summerset Drive Midland. Michigan 48640 Mr. Paul A. Perry. Secretary Consumers Power Company Stewart H. Freeman 212 W. Michigan Avenue Assistant Attorney General Jackson Michigan 49201 State of Michigan Environmental Protection Division Mr. Walt Apley 720 Law Building c/o Mr. Max Clausen Lansing. Michigan 48913 Battelle Pacific North West Labs (PNWL) Battelle Blvd. Mr. Wendell Marshall SIGMA IV Building Route 10-Richland. Washington 99352 Midland. Michigan 48640 Mr. 1. Charak. Manager Mr. Roger W. Huston NRC Assista'nce Project Argonne National Laboratory Suite 220 7910 Woodmont Avenue 9700 South Cass Avenue Bethesda. " Maryland 20814 Argonne. Illinois 60439 Mr. R. B. Borsum Nuclear Power Generation Division Babcock & Wilcox 7910 Woodmont Avenue. Suite 220 Bethesda. Maryland 20814 f 9 ,e ...,-,---..-,-._.,-.r-.,----,,--,,--..--,+.,.,-,.e,.,mm,- +,,.. - -,,,, w..__--,,4%,---..---,..m, e -m., w a----,-,,,,--.-,,w%w
Mr. J. W. Cook * ~ cc: Commander, Naval Surface Weapons Center ATTN: P. C. Huang Whitee 0ak Silver Spring, Maryland 20910 Mr. L. J. Auge, Manager Facility. Design Engineering Energy Technology Engineering Center P.O. Box 1449 Canoga Park, Californ.ia 91304 Mr. William Lawhead U.S. Corps of Engineers NCEED - T 7th Floor 477 Michigan Avenue Detroit, Michigan 48226 Charles Bechhoefer, Esq. Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. Ralph S. Decker Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C. 20555 ~ Dr. Frederick P. Cowan Apt. B-125 6125 N. Verde Trail Boca Raton, Florida 33433 Jerry Harbour, Esq. Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C. 20555 e 5 ~
!r ue .[ [,s E o,, UNITED STATES NUCLEAR REGULATORY COMMISSION f o .i WASHINGTON, D. C. 20555 N PRIF U PAL STAFF ,,.....,o m o mi m i ms i Docket Nos: 50-329 > /0 l' and 50-330 ~ 'ro \\ DE6TT APPLICANT: CONSUMERS POWER COMPANY D FACILITY: Midland Plant, Units 1 and 2
SUBJECT:
SUMMARY
OF MEETING TO DISCUSS REMEDIAL PLANS FOR AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PIT FOUNDATIONS On November 4,1981, the NRC staff and their consultants met in Bethesda with Consumers Power Cocpany (CPC) representatives and their consultants to discuss remedial plans for auxiliary building and feedwater isolation valve pit founda-tions. A list of attendees is attached as Enclosure 1 and the meeting agenda is attached as Enclosure 2. The following provides a summary of the meeting. E. Adensam stated that the Midland project manager and his backup were not available, and therefore, K. Jabbour would coordinate the meeting. OELD stated that the hearing testimony for Midland should be in the mail by November 17, 1981. Discussion of the seismic model is scheduled for December 14 - 18, 1981. It is expected that, during the hearings, the NRC staff will inform the Licensing Board on areas of agreement between Consumers and the staff. CPC stated that they started procurement for freeze wall hardware and access shaft. They invited the NRC staff to visit two work sites in Philadelphia and Louisiana where freeze wall technology is applied. A schedule of CPC work pro-gress is provided as Enclosure 3. Representatives of Mergentime and Ground Water Technology, Inc., discussed their plans for the Midland site, the freezing and grouting operations, and their experience in this area. They provided sketches of the access shaft, frozen earth membrane, proposed freeze wall locations, typical freeze element, and typical pressure and temperature monitor location. The sketches are attached as. They also stated that there is no problem with frost heaving and committed to produce data on heaving. D b Ol M &:uy,
1 2-Following the presentation above, the attendees discussed the staff questions as stated in Enclosures 5 and 6. The NRC Structural Engineering Branch offered to provide their questions to Consumers on November 5,1981. At the conclusion of the meeting, Consumers committed to provide written responses to the questions in. These responses were provided in a letter from CPC to H. R. Denton dated November 16, 1981. h4 M-Kahtan Jabbour. Project Manager Licensing Branch No. 4 Division of Licensing-
Enclosures:
As stated cc: See next page j I i 2 1
i MIDLAND L Mr. 'J. W. Cook Vice President Consumers Power Cogany 1945 West Parnall Road Jackson. Michigan 49201 ,,'j cc: Michael I. Miller. Esq. Mr. Don van Farrowe. Chief Ronald G. Zamarin. Esq. Division of Radiological Health 3 Alan S. Farnell Esq. Department of Public Health ,j Isham. Lincoln & Beale P.O. Box 33035 '1 Suite 4200 Lansing. Michigan 48909 1 First National Plaza Chicago. Illinois 60603 William J. Scanlon. Esq. 2034 Pauline Boulevard ,1 James E. Brunner. Esq. Ann Arbor. Michigan 48103 j Consumers Power Cogany 212 West Michigan Avenue U.S. Nuclear Regulatory Connission ~1 Jackson. Michigan 49201 Resident Inspectors Office Route 7 Myron M. Cherry. Esq. Midland. Michigan 48640 1 1 IBM Plaza Chicago Illinois 60611 Ms. Barbara Stamiris 5795 N. River a Ms. Mary Sinclair Freeland.' Michigan 48623 5711 Summerset Drive Midland. Michigan 48640 Mr. Paul A. Perry. Secretary Consumers Power Company Stewart H. Freeman 212 W. Michigan Avenue Assistant Attorney General Jackson. Michigan 49201
- i State of Michigan Environmental
- j Protection Division Mr. Walt Apley l
720 Law Building c/o Mr. Max Clausen i Lansing. Michigan 48913 Battelle Pacific North West Labs (PNWL)
- I Battelle Blvd.
l Mr. Wendell Marshall SIGMA IV Building ili Route 10 Richland. Washington 99352 Midiand Michigan 48640 Mr. I. Charak. Manager Mr. Roger W. Huston NRC Assistance Project Suite 220 Argonne National Laboratory
- l 7910 Woodmont Avenue 9700 South Cass Avenue l'
l Bethesda. " Maryland 20814 Argonne. Illinois 60439 Mr. R. B. Borsum Nuclear Power Generation Division i Babcock 8 Wilcox 7910 Woodmont Avenue. Suite 220 Bethesda. Maryland 20814 .i
I' ' - il 5 List of Attendees 6 l November 4. 1981_ J NRC Consumers Power Company .I-j K. Jabsour K. Razdan E. Adensam* G. Keely i I J. Kar,e N. Ramanujam i A. Hodgdon W. Paton* Bechtel 1 F..Rinaldi G. Lear B. Dhar i F. Schauer* S. Afifi M. Blume* N. Swanberg NRC Consultants Hanson Engineers H. Singh D. Bartlett i : J. Matra
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F. Williams Mergentime C. Gould Ground Water Tech. Inc. i D. Maishman 'I H Mueser Rutledge I I i; J. Gould il 1
- Denotes part-time participation 1
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4 4.,. A i e s 3 November 4, 1981 it Meeting with NRC Staff g on Midland Plant Auxiliary Building !i !
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~ MILESTONES POR AUXILIARY BUILDING AND PEEDWATER ISOLATION VALVE 4 i PIT Ut'DERPINNING 9 ITEM START DATE L1. s 1. Procurement of Pressewall Bardware In Process ii l 2. Award of subcontract for Underpinning 12/15/81 (three phases of work) 3. Start installation of Freesewall 12/29/81 (Phase 1 of subcontract) !) 4. Mobilise and start installation of access 1/15/82 i shaft to el. 609 feet (Phase 2 of subcontract) 5. Complete structural analysis for construction 1/1/82 underpinning 6. Award of subcontract for Instrumentation 12/1/81 )', (Design, furnish, install and monitor) j : 7. Start drifting for Underpinning 2/15/82
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(Phase 3 of subcontract) }# 8. Drill and develop additional 44 permanent In Process wells 9. Start Recharge Test 11/25/81
- 10. Structural Acceptance Criteria for 2/15/82 long term settlement
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l RECORD OF TELEPHONE CONVERSATIONS Date: October 30, 1981 Project: Midland 50-330 Recorded by: Joseph D. Kane Talked With: CPCo Bechtel NRC COE D. Budzik A,. Boos R. Landsman H. Singh G. Keeley N. Swanberg F. Rinaldi D. Hood J. Kane l Route To: For Information i i G. Lear i L. Heller j D. Hood i W. Paton i F. Rinaldi R. Landsman, I&E, Region III H. Singh, COE, Chicago J. Kane l Hain Subject of Call: Remedial Underpinning of Auxiliary Building and l Feedwater Isolation Valve Pits Items Discussed: i
- 1. to CPCo September 30,1981. submittal from J. W. Cook to H. R. Denton entitled " Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits". During the October 30, 1981 conference call CPCo was requested to respond to the following questions which had been developed in the COE/NRC review of Enclosure 3.
relative to geotechnical engineering aspects in underpinning the Auxiliary Building. Q.l. (Pg. 2 Sect. 4, 2nd Para.) Please define " design jacking force," how established and the duration that it will be held? Q.2. (Pg. 2. Sect. 4, 3rd Para.) Discuss and provide detail of dowel connection. (Diameter,howdistributedalongwall,lengthof embedment,etc). Q.3. (Pg.3. Sect.5.1,lastpara) The agreed upon acceptance criteria i for soil particle monitoring during dewatering requires 0.005 m and not 0.05 m. Correction by CPCo required. l o
e E !q l Q.4. (Pq. 3 Sect. 5.1, Para. b) Installing the frozen cutoff membrane wi'1 cause expansion and possibly increase the soil voids. When* ultimately unfrozen, what is the effect (e.g., further settlement) on safety related structures, conduits and piping. Provide discussion on the basic system of the frozen membrane [ size and spacing of holes to be drilled, method for pumping brine into foundation layers, range of temperatures that are critical to wall stability which are to be monitored, decomissioning (e.g., grouting, etc)]. il Q.5. (Pg. 3. Sect. 5.2) C1arify the procedure to be used in post tensioning i! the Electrical Penetration Area. Where will the buoyancy force be transmitted to the foundation and in what manner?
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Q.6. (Pg. 4 Sect. 5.6, 2nd Para.) Please explain the meaning of " failure nearing capacity factors" and the basis for "the nine times the shear strength for the cone"? Q.7. (Pg. 4 Sect. 5.b. 4th Para.) How will the equivalent soil modulus be detennined? What is the depth that the measured settlement will lI be distributed over and what is the area to be used in determining the stress? ll il Q.8. (Pg. 4 Sect. 6) Presently, this paragraph implies that crack monitoring will not be performed on the existing structure. Please correct. Before remedial underpinning begins an accurate and up-to-date record of cracks should be developed for those safety related i structures which could potentially be affected by the underpinning operations. This background record should be verified by 18E inspection and could serve as the basis for evaluating any changes in cracks due l to underpinning operations. i Q.9. (Pg.5. Sect 6.1.1and6.1.2) When will the acceptance criteria for .l the differential and absolute settlement be provided to the NRC7 Q.10. (Pg. 5, Sect. 6.2) Provide the basis for establishing the crack width of 0.03 inch. Appendix D should also address crack monitoring requirements during underpinning (frequency of reading, format for l presenting observations, action levels etc). 1 Q.ll. (Pg. 6. Sect. 7.2.1,'last Para.) Provide discussion why the drained shear strength is not required to be considered in analyzing for adequate bearing capacity. Also in the last paragraph in Section 7.2.1, Pg. 7 indicate the basis for the 2 days and what would be required if the settlement rate does not reach a straight: line trend ) in 2 days. j q Q.12. (Pg.7. Sect.7.2.2) Where are the WCC controlled rebound-reload cycle soil test results? What is the corresponding stress level with j a secant modulus of elasticity equal to 3500 KSF? 1 s.
,-.g Q.13. (Pg. 8. Sect 7.2.3, 1st Para.) The estimates of settlement using the referenced NAVFAC DM-7 do not include secondary consolidation. What secondary consolidation would be indicated if the consolidation test results using the appropriate load increment were used? Compare this estimate with valves for pennanent wall conditions "after jacking, long term". Please provide basis for the three estimated settlement valves for " Load transfer points for temporary load to reactor footing".at the bottom of pg. 8 and discuss any effects of this settlement on the reactor and pipe connections. il Q.14. (Pg A-1, Sect.1, 2nd Par.) Please indicate how the soil spring !l constants were established for long tenn loads. N Q.15. (Pg C-2, last Par. and Pg. C-6 Par. 8) What are the protective 1 construction measures planned for the Turbine Building and Buttress
- 1 Access Shafts and when will they be placed? Please provide discussion on the sequence of operations to complete the drift beneath the
- I Turbine Building and show sectional views of this work with respect to the Turbine Building foundations and affected piping and conduits.
Q.16. (PgC-3, Par.A.1.a) Please explain what is meant by minimizing the amount of concrete to be removed. Q.17. (Pg. C-3, Par. A.1.c. and A.1.d) What is the magnitude of the load for testing the temporary support pier and how was it established. and how will it be applied? Is the EPA foundation slab capable of supporting this load at this time? Q.18. (Pg. C-4, Sect. A.1.f.,1st complete para.) Provide discussion on monitoring of the control tower behavior at this time. What criteria will be used to decide if preload should be stopped and support capacity should be~added to the control tower? Q.19. (Pg.C-4, Sect.A.2.) What are the reasons why the three temporary supports under the EPA should not be completed before the pennanent li support at the control tower is initiated? Q.20. (Pg.C-4. Sect.A.3.a) Questions are raised as to whether the EPA structure can withstand the overhang condition which results if the initial temporary supports is assumed to fail. What is the basis and n! need for this extreme assumption? Is the EPA structure capable of 'j withstanding this loading condition? Q.21. (Pg.C-4,SectA.3.bandA.3.c) The distinction between 3.b and 3.c j is unclear. What is the magnitude of the load for testing and how j established? Is there a problem with the EPA foundation slab providing a sufficient reaction load? 3 Q.22. (Pg. C-5, Sect.14 and 15) It appears the operations described in l these items are intended only for the wings and not the control tower. How is the load test and load transfer for the control tower to be completed. For the long term load test on the wings, what is the load magnitude and how was it established? What is the final s -r .,-,---.,----__-~_.._,.,-._,_,x.-_.
g 3 e. y \\ ~ 4 N-sequence of operations in transferring the structure load to the pemanent underpinning. - Q.23. (Pg. D-1 Sect 1.0, 2nd Par) Describe the procedure that relates allowable stresses and allowable strains with structure movements that are being monitored. Q.24.; (Pg D-2, Sect.1, 3rd Par.) Please clarify the distinction between the first and second layer systems for detecting structure movement. 3j' Q.25. (Pg D-2 Sect.1, 4th' 6th, and 7th Para.) Please provide elevations and sectional views with typical details for the deep seated bench i, mark and the instrumentation for monitoring relative horizontal ] movement and absolute horizontal movement. j Q.26. (Pg. D.3, Sect. 2, 2nd Par.) Please clarify the explanation why the hydraulic pressure data cannet be used to measure load. i y Q.27. (Pg.D-3, Sect.2,3rdPar.) Provide sectional view of set up for p measuring difference in relative position. How does this procedure S address the possibility of both the underpinning element and structare a settling? Provide the basis for maintaining the jack / hydraulic system for 1 hour and for establishing the 0.01 inch movement.
- f 0.28.
(Pg.D-4, Sect.2,4thPara.) When will the modeling and critical d structural stresses and strains be detemined and furnished to the NRC7 Q.29. (Pg D-5, Sect. 2, 2ad and 3rd Para.) Provide sketch and locations with typical details of instrumentation for measuring concrete e, stress, tell tale devices and predetermined points for monitoring g vertical movement-u P] 0.30. (Pgs. D-5 and D-6. Sect. 3. Par. 3A.1, 3A.2, 3A.3) For the various types of monitoring described in these paragraphs provide an example i of the fonas to be used for plotting the recorded data. What are the predetermined levels of movements which would require adjustments and/or action by the onsite geotechnical engineer. Identify any L specific instrumentation which would be continued to be read during q~ plant operation and which eventually will be addressed by a Technical Specification. 2. C6nsumers was notified that the above questions do not contain the COE/NRC review consnents on the labcratory test results for foundation soils beneath ( the Auxiliary Building. The COE/NRC coments on the test results will be furnished at a later date following CPCo submittal of the Part II lab test report which is expected to be submitted to the NRC the week of November 2,1981, n ~ 4 3. Consumers indicated the questions asked in the conference call of October 30,1981 L would be addressed as far as possible in the upcoming meeting with NRC in h Bethesda on November 4, 1981. n L ?
y Staff Questions from 10/30/31 Telecon I. 1. Paranraoh 4.0. name 2 h e is design jacking force; how i established; how long held? 2. What are details of dowels; dia., 6 spacing, and embedaant length? 3. Para 5.1. pane 3 Shouldn't 0.05 be M 7 I h e are consequences of settling of structure in region of freesewall when it is " thawed"? Basic description of system, e.g. layout, i asterials, temperatures, decommissioning. u Il 4. Para 5.2. osse 3 h re will the buoyancy forces be transmitted to structure? i } 5. Pars 5.6. name 4 Define failure bearing capacity and how j. was value of 9 established. I i-Bow will equivalent soils modulus be computed? At what depth will equivalent strain be calculated and what is corresponding stresa at that level? 6. Para 6.0. osse 4 h e is date for last auxiliary building i, crack mapping? ht are the plans for crack monitoring during construction and will be establish a baseline? }' How are we going to monitor cracks in inaccessible areas? I s Pers 6.1.1 osse 5 h e will the program for differential and absolute settlement of structures be established including acceptance criteria? 1 Para 6.1.2. pane 5 h n will the program for monitoring under-pinning during jacking be established including acceptance criteria? Para 6.2. pane 5 Justify crack widths stated. Para 7.2.1. pase 6 Justify why drained shear strengths were l j not used to determine bearing capacity. i l Para 7.2.1. name 7, h e are the plans if rate doesn't reach a l l straight line after 2 days? i t \\l
Staff Questions Page 2 ~ ~ i 7. Para 7.2.2. page 7 Where is cyclic testing reported? How was the modulus of 3500 ksf obtained? I 8. Para 7.2.3. Dage 8 What settlement is to be attributed to secondary consolidation (NAVAC reference is elastic; it does not cover effects of secondary consolidation)? f How were settlements after jacking values given 'in table determined?
- g How were settlement values during temporary 1.uding on reactor buliding estimated?
l: What is effect on reactor building and pipe connections? 9. Appendix A How were static long-term springs established?
- l Para 1.0. page A-1 i'
- 10. Appendix C What are protective construction details; Last para, page C-2 where support placed; when installed?
What about details of turbine building underpinning and its effect on buried Category I utilities in this area?
- 11. Page C-3 Discuss turbine building underpinning.
12. Item 1-a What is meant by " minimizing" concrete removal? 13. Item 1-c Give details of load test (what is load; how arrived at; and how applied). P 14. Item 1-d Justify your statement about building performance as propped cantilever. f
- 15. Page C-4 What are we doing to monitor performance Item 1-f of control tower? What are the criteria and if a problem occurs, then what action j,
is taken? tI 16. Item 2 Rationale behind not completing all 3
- j needle beams on electrical penetration area before starting pit control tower 1
area.
- 17. Item 3 Can electrical penetration area support an assumed failure of the end beam?
Cive details of test load and relate it to the design load. What are differences between 3b and 3c?
.. f. g.* ' Staff Questions Page 3
- 18. Pane C-5 What is load test and load transfer program Item 4 for control tower?
19. Item 14 What is the load, how established, settlement acceptance criteria?
- 20. Appendiz D State program for correlating allowable Page D-1, 2nd para strains and stresses.
23. Page D-2 Discuss first layer and second layer
- j movement monitoring.
Give details of deep benchmark datum. Provide details of horizontal movement monitoring. J,.l'
- 22. Page D-3. para 2.0 Need better definition of hydraulic jacking j.
program. 'l Want sketch of setup for overall (building and underpinning) settling monitoring setup. What is basis for 1 hour and 0.01 inch?
- 23. Page D-4 How will stress and strain be correlated?
- 24. Pane D-5 Give details on telltale setup and Carlson e
stress meters. Give details of settling monitoring points at and of electrical penetration area. ~
- 25. Para 3.0 (A)
For each of 3A1, 2, 3, indicate:
- i Data to be taken, what are predetermined allowable limits, how these limits are I.'
established, and action to be taken if these limits are reached. lfle Which measurements will be included in technical specs? I 1'i i o I ~
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C
t / C011SumBIS Power - w c.* Vice President - Projects, Engineen'ng and Construction General offices: 1945 West Pernell Road, Jackson, MI 49201 + (517) 788 o453 December 3, 1981 1 PRINCIPAL pTAFF _] [bic Ju !nn j ,in i l S ' '...w$'. O I E P! Harold R Denton, Director 3'[L RfbillG R vbTI Office of Nuclear Reactor Regulation {ppy US Nuclear Regulatory Commission
- 713, Washington, DC 20555 MIDLAND PROJECT MIDLAND DOCKET NOS 50-329, 50-330 UNDERPINNING OF THE AUXILIARY BUILDING - CALCULATIONAL RESULTS FILE 0485.16, B3.0.1 SERIAL 14899
REFERENCE:
JWC00K TO HRDENTON, SERIAL 14110, DATED SEPTEMBER 30, 1981 ENCLOSURE: ADDENDUM TO TECHNICAL REPORT ON UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS Attached to the above-referenced correspondence of September 30, 1981, e submitted a design report entitled, " Technical Report on Underpinning t! e Auxiliary Building and Feedwater Isolation Valve Pits." We are providing as an enclosure to this correspondence twenty-five (25) copies of an addendum to the above-referenced technical report. The purpose of the enclosed addendum is to supplement Section 7.5 of the above-referenced technical report and Appendix A of the same document. The enclosed addendum contains the following information: 1. Soil pressure data under the auxiliary building and the feedwater isolation valve pits underpinning area. 2. Load combinations used for preliminary design of the underpinning reinforcement walls and the connection joints of the underpinning walls to the auxiliary building. 3. Design forces and moments at the critical sections. 4. Reinforcement details provided in the underpinning walls. <[ \\ oc1181-0495a100 Eh MCOH e IG,& l
2 ~ 5. A summary of results from recent preliminary auxiliary building structural analyses which reflect the modified' dynamic model of the structure, actual natural soils properties and the proposed underpinnings. These results identify certain areas within the structure which may require some modification in order to meet design requirements. As further analyses are completed, we will forward our proposed plans for any additional remedial actions to the Staff for their review and concurrence. The material presented in this addendum is based on preliminary analyses of the-permanent underpinning configuration. Detailed calculational checks will be performed as a part of the final analysis to verify the design adequacy. ~ We are also currently performing analyses and design checks for the auxiliary building construction condition for various construction stages. The results of these detailed design checks for both the permanent underpinning configuration and the construction condition will be available to the NRC Staff for their audit in accordance with agreements reached at our November 17, 1981 meeting in Bethesda. This addendum along with our previous submittals and discussions with the NRC Staff should adequately respond to the concerns identified by the Staff. We believe this information continues to support our conclusion that the design of the auxiliary building and feedwater isolation valve pit structures combined with the proposed underpinning remedial actions are adequate and appropriate for these structures. JWC/WJC/RLT/dsb [ AtomicSafetyandLicensingAppealBokrd,w/o CC CBechhoefer, ASLB, w/o MMCherry, Esq, w/o FPCowan, ASLB, w/o RJCook, Midland Resident Inspector, w/o RSDecker, ASLB, w/o SGadler, w/o i JHarbour, ASLB, w/o DSHood, NRC, w/a (2) DFJudd, B&W, w/o JDKane, NRC, w/a FJKelley, Esq, w/o RBLandsman, NRC Region III, w/a WHMarshall, Esq, w/o JPMatra,' Naval Surface Weapons Center, w/a W0tto, Army Corps of Engineers, w/a WDPaton, Esq, w/o FRinaldi, NRC, w/a HSingh, Army Corps of Engineers, w/a BStamiris, w/o i oc1181-0495a100 ., _._ _ - - _ -- -.-..--~-_.--._ _.-- - - - - - - -
c. l l ADDENDUM TO TECHNICAL REPORT ON UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS s' CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 AND 2 DECDGER 2,1981
- '! l,' 5 7 -
a
MIDLAND PLANT UNITS 1 AND 2 ADDENDUM TO TECHNICAL REPORT-CN UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS CONTENTS
1.0 INTRODUCTION
1 -2.0 SOIL PRESSURES 1 3.0 UNDERPINNING WALL DESIGN 3 4.0 STABILITY 4 5.0 CONNECTION DETAIL 4 6.0 EXISTING STRUCTURE 4 REFERENCES ii
\\ i MIDLAND PLANT UNITS 1 AND 2 ADDENDUM TO TECHNICAL REPORT ON UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS k ' l.0 INTRODUCTION The purpose of this addendum is to supplement Section 7.5 of the - Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits (Reference 1) with the following i information: l a. Soil pressure data under the auxiliary building, 1 feedwater isolation valve pits (FIVPs), and auxiliary building underpinning b. Load combinations used for preliminary design of the underpinning reinforcement and the connection of the underpinning to the auxiliary building c. Design forces and moments at the design sections d. Reinforcement provided in the underpinning walls e. Identification of the areas of potential overstress in j the auxiliary building as indicated by the preliminary analysis The material presented herein is based on preliminary analyses and design for the permanent underpinned configuration of the auxiliary building and the FIVPs. Detailed checking will be performed after final analysis to verify the design adequacy. The results of this detailed check will be provided later in an audit scheduled for May 17, 1982. The results of the analysis for the construction condition with temporary support piers are not included. This analysis is in progress and the results will be provided later for the audit scheduled January 15, 1982. 2.0 SOIL PRESSURES 2.1 AUXILIARY BUILDING UNDERPINNING Table.1 and Figure 1 show the magnitudy and location of the net soil pressure under the main auxiliary building and underpinning under the control tower and the electrical penetration area. The soil pressures were computed for the following load combination considered to be critical for preliminary analysis. D + L + R + E' + Pg where D = dead load i 1
Midland Plant Units 1 and 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits L = live load R = pipe break load E' = safe shutdown earthquake (SSE) loads corresponding to the ground acceleration given in the Midland FSAR Section 3.7 This load combination corresponds to the 19th load combination in Table 1 of Reference 1 without the thermal loads which are neglected in the preliminary design. The allowable net bearing pressure is based on the allowable values submitted to the NRC in Subsection 7.2.1 of Reference 1 and Midland FSAR Section 2.5. 2.2 FEEDWATER ISOLATION VALVE PITS The FIVPs will be supported on engineered sand backfill. A 3-foot thick concrete slab will be provided between the bottom of j the pit and the top of the sand, as shown in Figure 2. The sand will be confined between the reactor building, electrical penetration area underpinning wall, turbine building j underpinning, and buttress access shaft. The slab at the top of the engineered backfill will be jacked against the existing FIVP base slab. This jacking will minimize any future settlement due to compaction of the engineered backfill ~from the weight of the 4 FIVP. After jacking, the space between the 3-foot slab and the bottom of the pit will be filled with concrete grout. The maximum bearing pressures on the engineered backfill are shown in Table 2. .The soil pressures (shown in Table 2) were computed for the j following critical load combination considered in the preliminary analysis: I D+L+E' +P I' L This load combination corresponds to the 19th load combination in Table 1 of Reference 1 without the thermal loads which are neglected in the preliminary design. 2 ~.
~ Midland Plant Units 1 and 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits '3.0 UNDERPINNING WALL DESIGN 3.1 LOADS The preliminary wall design is based on the following loads and load combinations: a. U = 1.4D + 1.7L + Pn(corresponds to the fifth case in Table 1 of Reference 1) b.- U = D + L + R + 1.5E' + Pg For the above load combinations, the following loads have been considered: a. Dead load - Includes soil pressure loads. b. Jacking load applied as uniform load along the length of the underpinning c. Live load d. Seismic loads e. Pipe break loads 3.2 UNDERPINNING BELOW THE ELECTRICAL PENETRATION AREA The underpinning wall under the electrical penetration areas will carry the vertical loads which will be transferred to clay till at el 571'. The walls will also carry lateral loads due to seismic forces, soil pressure, and surcharge from the turbine building. These lateral loads will be resisted by the engineered sand backfill placed between the underpinning wall and the reactor building, as shown in Figure 4, and the friction between the concrete wall and the soil underneath (clay till). The net lateral loads in the second load combination exceed the available friction between the wall and soil. For this reason, an ll-foot wide, horizontal beam has been provided to resist the bending due to the net lateral loads (Figure 4). i The critical section for the wall is near column lines 5.3 and 7.8 (see Figure 3). The design forces are shown in Table 3 and reinforcement is presented in Figure 3. 3
Midland Plant Units 1 and 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits '3.3 ' UNDERPINNING BELOW THE CONTROL TOWER -The underpinning wall will be embedded in natural clay till between elevations 571 and 562, and will be restrained by a new slab at el 583'-6" to be constructed as shown in Figure 4. The space between el 571' and the slab at el 583'-6" will be backfilled with engineered granular material. Part of the lateral loads will be resisted by the clay till between elevations 571 and 562, and the balance will be transferred to the main building by the slab at el 583'-6". The critical section for the wall is at column line 7.8. The location of the critical sections and reinforcement are presented in Figure 3. Design loads at the critical section are presented in Table 3. 4.0 STABILITY The factors of safety against sliding and overturning are shown in Subsection 3.8.6.3.4 of the Midland FSAR (Reference 2). In the underpinned condition, the overall safety factors against sliding and overturning are expected to reduce or remain unchanged from the values shown in the Midland FSAR. l-5.0 CONNECTION DETAIL The connection of the underpinning to the auxiliary building will be designed to transfer shear and tension resulting from the seismic lateral loads and other concurrent loads. The design loads are presented in Table 3. The type and arrangement of dowels required for the connection are being finalized and i will be provided during the structural audits. At first, the dowels will be grouted only on one side, either at the building or the underpinning. The other side will be grouted i only after jacking loads are applied and held. To achieve this for the horizontal dowels, the end portion of the underpinning wall will be poured after jacking loads are applied and held long enough for the till to be within secondary compression. 6.O EXISTING STRUCTURE Based on a preliminary analysis, the following areas between column lines G and H appear to be overstressed: a. Slab at el 659' 4
~ Midland Plant Units 1 and 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits b. Shear walls on column lines 5.6 and 7.8 between elevations Sb4' and 614' c. West staircase wall on column line 5.3 between elevations 646' and 685' d. Walls on column lines 5.8 and 7.2 from elevations 659' to 699' The above mentioned areas will be structurally upgraded to withstand all loads including 1.5 x E' if the more rigorous final analysis still indicates that these areas are overstressed. 5
AUXILIARY BUILDING UNDERPINNING ~ ~ ~ e ~ R i /J u / Y,,.7,2$// hk9 h,,,, ) Q )77/ /// //D7'? l ""1T'*g l ef(,. i cof l g s oo reme CONSUMERS POWER COMPANY l C MIDLAND PLANT UNITS 1 & 2 S OIL PRESSURE DA TA POINTS FIGURE 1 1
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aan. AREA .+. .m-. m we,,g 7.- ,,e, - hee. h / asefsot TthaER We.seet C AdasuARY /mamam mm.. ei.e wa6L l r EL. 4 6410' SL.8 I4'-8"2 [ fSL 680'.0" ,,,,/,..~u~-~ ~- s m 5,..** .e:**.:..: s l peLL h tassesLAR tacmHLL
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NET Soll PRESSURE fcSF) ULT. NET D+ L+ R + E% P D+L+R+Pu BEARING POINT CAPACITY y m) EL. CASE 1 CASE 2 (KSF) A 609'-0 .... -3.4
- 0. 8,
-1.3 30 B 609'-0 -2 4_ -0.3 -1.3 30 1 .C 630'-6" ~ 1.Y " -3.7, -1.2 15 D 562'-0 -7.1 -5.3. -6.2 44 E 562'-0 -7.9 -3.9 -5.9 44 ~ D1 562'-0 -6.5 -2.3 -4.4 44 El 562'-0 _9,q _s.3 _4.1 44 i ' 6.6 44 D2 562'-0 -10.2 -3.0 E2 562'-0 44 -5.8 -6.8 -6.3 F 571'-0 -18.2 1.6(-3.0) -8.3 44 F1 571'-0 -15.3 -0.7 -8.0 44 F2 571'-0 .12.8 -2.8 -7.8 44 C 562'-0 -15.3 -4.7 -10.0 44 j H 562'-0 -12.7_ -7.3 -10.0 44 H1 562'-0 -7.6 -5.0 -6.3 44 J 562'-0 -9.9 ' -9.9 -9.9 44 ~ K 571'-0 -2.5 -13.5. -8.0 44 K1 571'-0 -7.8 44 . -5.2. - -10.4 K2 571'-0 -7.5 . -7.9 -7.7 44 l 1. Case 1 corresponds to maximum compression @ PT. F 2. Case 2 corresponds to minimum comp'ression @ PT. F 3. Gross soil pressure is given in parenthesis 4. Comprassion is negative Note: Net pressure is total pressure CONSUMERS POWER COMPANY l MIDLAND PLANT UNITS 1 & 2 l minus the pressure due to the AUX BLDG UNDERPINNING SOIL PRESSURE TABLE-1
~ 4 W B SOIL PRESSURE (KSF) D + L+ E' D+L POINT CASE I CASE 2 CASE 3 A 2.54 2.96 -3.07 B -7.16 -6.52 -4.68 C -10.83 -10.12 -5.27 D -7.41 -6.78 -4.68 E 0.39 0.85 -3.40
- 1) CASE 1 CORRESPONDS TO MAX. COMPRESSION
- 2) CASE 2 CORRESPONDS TO MIN. COMPRESSION
- 3) COMPRESSION IS NEGATIVE l
l
- 4) ULTIMATE BEARING CAPACITY = 25 KSF IESTIMATED MINIMUM VALUE)
CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 FIVP SOIL PRESSURES TA B L E - 2
l' W UNDERPINNING WALLS in pt,ng L OCATION LOAD A XIA L ' MOM'T MOM'T SHEAR SHEAR P P (SEE FIG. 3) COMB. K/FT K-FT/FT TJp K/FT ffp; M I 358 -387 1 816 22.6 1278 gg i M 1 -48.5 -27.4 1 968 22.6 1318 g 7 h 1 278 370 t 969 -29.8 t358 3g I h I -122. 30.1 .t1100 -29.8 1318 g INTERFA CES <t..d ca.b. 2> LOCATION A XIA L SHEAR SHEAR C A P. INTERFACE K/F T K/F T K/F T M (FIG. 3) HOR IZ 15.7 117 VERT 12.7 79.7 2 (FIG.1) LOAD COMBINATIONS: ~ 1. U = 1.4 D + 1.7 L +Pu 2. U = D + L + R + 1.5 E% P NOTEd)THE CAPACITIES CORRESPOND TO THE EXISTING AXIA L L OADS. 2)+VE AXIAL 1.0AD IS TENSION 3)THE CRITICAL OUT OF PLANE SHEAR IN THf UNDERPINNING WALL IS 21.3k/ft WHILE THE CAPACITY IS 94k/ft
- THE TYPE AND SPACING OF DOWELS WILL BE FINALIZED I CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 Aux. Bldg. Underpinning Design Loads Table 3
TG /gf *Uu y g UNITED STATES gnw 8 NUCLEAR REGULATORY COMMISSION /7 o b+" S .j WASHINGTON, D. C. 20555 m \\...../ NOV 2 41981 c2gT Docket Nos: 50-329 OM, OL '^U and 50-330 o/D UD. W i/FI Mr. J. W. Cook L Vice President 3,3 71 Consumers Power Company 1945 West Parnall Road
- PFE,
-g,1 Jackson, Michigan 49201
Dear Mr. Cook:
Subject:
Staff Concurrence for Construction of Access Shafts and Freeze Wall in Preparation for Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits During several meetings with the NRC staff, including more recently those on October 1 ano November 4,1981, members of Consun'ers Power Company (CPCo) and consultants have described the underpinning planned beneath the electrical penetration areas and the. control tower portions of the.
- s auxiliary building and beneath the adjacent feedwater isolation valve pits for Midland Plant, Units 1 and 2.
These discussions have included the fact that in order to prepare for implementing the underpinning scheme, vertical access shafts on the east and west ends of the auxili.ary building and ad acent J to each feedwater valve pit and the turbine building must first be constructed fro,a plant grade (elevation 634 feet). down to elevation 609. In adaition, a freezewall is necessary to augaent the present consi.ruction desatering sche;n. The general locations of the access shafts and freezewall are shown on Enclosures 1 and 2. Your letters of October 28 and November 16, 1981 have responded to rMC requests for additional information and have requested staff concurrence to proceed with construction of the access shafts and freezewall. Our review recognizes ~tnat tne vertical portion of the access shaf t will not undermine any existing structure. The shafts and the freezewall can be abandoned at any time and will be backfilleo with concrete or soil upon completion of the underpinning activity. Accordingly,4.nis activity does not represent an irre-versible commitment. It also has no effect on any other remedial action that may be required as a result of the staff's continuing review of subsequent phases of the underpinning scheme or as a result of the staff's OL review or the OM-OL hearing. Our review furtner recognizes the commitment of your staff that Region III personnel will be notified prior to drilling near seismic Category I underground utilities an,d structures. In view of the above, the NRC staff concurs with your plans to begin construction of the vertical access shaft down to elevation 609_ and installation of the freeze wall hardware. D 3 01981 e.o v ~wo Q, N' p' 1
e Mr. J. ' W. Cook' - A later phase of your underpinning work is understood to involve excavation beneath the valve pit structures, and extending the access shaft deep r to permit excavation along the turbine building for eventual access beneath the - auxiliary building. However, this later phase requires submittal of further information for staff review and approval and cur above concurrence does not authorize excavation directly beneath any structure. Similarly, our review of the effects of operation of the freezewall involves submittal of adoitional information (e.g., potential heave and resettlement) and our above concurrence is limited to installation of the freezewall, and does not include its activation. The additional infonnation associated with these later phases will be discussed by tne staff during the 014-0L hearing session beginning December 1981. Sincerely, ~ d%g Rooert L. Tedesco, Assistant Director for Licensing Division of Licensing Enclosure (s): As stateo cc: See next page M f 6 e
4 MIDLAND - Mr. J. W. Cook Vice President Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201-cc: Michael I. Miller, Esq. Mr. Don van Farrowe, Chief Ronald G. Zamarin, Esq. Division of Radiological Health Alan S. Farnell, Esq. Department of Public Health Isham, Lincoln & Beale P.O. Box 33035 Suite 4200 Lansing,, Michigan 48909 1 First National Plaza
- Chicago, Illinois 60603 William J. Scanlon, Esq.
2034 Pauline Boulevard James E. Brunner, Esq. Ann Arbor, Michigan 48103 Consumers Power Company 212 West Michigan Avenue U.S. Nuclear Regulatory Commission Jackson, Michigan 49201 Resident Inspectors Office Route 7 Myron M. Cherry,- Esq. Midland, Michigan 48640 1 IBM Plaza Chicago, Illinois 60611 Ms. Barbara Stamiris 5795 N. River ,s,. '.Ms. Mary Sinclair Freeland, Michigan 48623 5711 Summerset Drive Midland, Michigan 48640 Mr. Paul A. Perry, Secretary Consumers Power Company Stawart H. Freeman 212 W. Michigan Avenue Assistant Attorney General Jackson, Michigan 49201 State of Michigan Environmental Protection Division Mr. Walt Apley 720 Law Building c/o Mr. Max Clausen Lansing, Michigan 48913 Battelle Pacific North' West. Labs (PNWL) Battelle Blvd. Mr. Wendell Marshall SIGMA IV Building Route 10 Richland, Washington 99352. Midland, Michigan 48640 Mr. I. Charak, Manager Mr. Steve Gadler NRC Assistance Project 2120 Carter Avenue Argonne National Laboratory St. Paul, Minnesota 55108 9700 South Cass Avenue Argonne, Illinois 60439 Mr. Roger W. Huston Suite 220 Mr. R. B. Borsum 7910 Woodmont Avenue Nuclear Power Generation Division Bethesda, Maryland 20814 Babcock & Wilcox 7910 Woodmont Aver.ye, Suite 220 Bethesda, Maryland 20814 l e g .-r., ,g_.., 9 .mm ,__y,- ,,._,gy,-,,, , _, -., -y,_,._
Mr. J., W.' Cook, .cc: Commander, Naval Surface Weapons Center ~ ATTN: P. C. Huang White Oak 511ver Spring, Maryland 20910 Mr. L. J. Auge, Manager - Facility Design Engineering Energy Technology Engineering Center P.O. Box 1449 Canoga Park, California 91304 Mr. William Lawhead U.S. Corps of Engineers NCEED - T 7th Floor 477' Michigan Avenue Detroit, Michigan 48226 Charles. Bechhoefer, Esq. Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission
- ": Washington, D. C.
20555 Mr. Ralph S. Decker Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C. 20555 Dr. Frederick P. Cowan Apt. B-125 6125 N. Verde Trail Boca Raton, Florida 33433 ~' Jerry Harbour, Esq. Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C. 20555 ~ M e e H q ~-,c. ,, - +,. - -,, - .,--------+-m, ,,.,,, - -,, ~ - - - - -,, - -,,,, -, -, -, -,,, -,, -- -w.,n,a m--nw,-
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