ML20030B585
| ML20030B585 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 08/14/1981 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Clark R, Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20030B586 | List: |
| References | |
| IEB-80-11, TAC-42896, TAC-42897, NUDOCS 8108180323 | |
| Download: ML20030B585 (61) | |
Text
,
WISCORSin Electnc POWER COMPANY 231 WEST MICHIGAN, MILWAUKEE, WISCONSIN 53201 August 14, 1981 Mr. H.
R.
Denton, Director Office of Nuclear Reactor Regulation 81/g'(
U. S. NUCLEAR REGULATORY COMMISSION 9
Washington, D. C.
20555 g
Attention:
Mr.
R.
7..
Clark, Chief Operati ng Reactors Branch 3 2p; AUS 1 i1981>
Gentlemen:
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DOCKET NOS. 50-266 AND 50-301 hA ADDITIONAL INFORMATION p
IE BULLETIN NO. 80-11, MASONRY WALLS y
POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 On June 9-11, 1981, members of your Staff met with W.";onsin Electric and our consultants at the Point Beach Nuclear Plant to conduct an on-site review and audit of our responses to IE Bulletin No. 80-11, Masonry Walls.
Discussions were held during this meeting to resolve differences between the NRC Staff's design criter.i a and the criteria used by Wisconsin Electric in evaluating the Point Beach masonry walls.
An end result of these discussions was the formation of 21 action items which would resolve the NRC's concerns regarding the analysis of masonry walls at the Point Beach Muclear Plant.
These action items were formally transmitted to us with Mr. Colburn's summary of meeting minutes dated July 1, 1981.
A number of these action items requested that information be provided to your Staff by August 15, 1981.
The enclosures to this letter provide our responses to action items 8, 15, 18, 19, and 20 of Mr. Colburn's summary.
Please contact us if you have say questions regarding this information.
Very truly yours, C/
/
}g C. W.
Fa,
irector Nuclear Power Department Enclosures g6 cn m, fn Nne Re sident Inspector I
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8108180323 810814 PDR ADOCK 05000266
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4 ACTION ITEM NO. 8 Walls subject to flexure in vertical direction shall be provided with positive anchor or equivalent at top and bottom or justification for no*: doing so will be provided for review by 08/15/81.
Also inicude the maximum tensile stresses normal to the bed joint due to out-of-plane loads for each wall.
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RESPONSE TO ACTION ITEM #8 In the plate analysis of the masonry walls, flexure requires cut-of-plane shear transfer along the boundaries of the wall.
When the plate analysis assumes support along the top edge and sides, positive anchorage is provided.
This is considered necessary oecause the mortar joint along these masonry-concrete interfaces are susceptible to shrinkage cracking.
Therefore these mortar joints may not be reliable for shear transfer.
When the plate analysis assumes support along the bottom edge, positive anchorage is not considered necessary for two reasons:
(1) This masonry-concrete interface is not likely to develop shrinkage cracks.
The dead weight of the wall prohibits the wall from shrinking away from its bottom boundary.
In-spection of the Point Beach masonry walls found no evidence of shrinkage cracks in these joints.
The adequacy of the mortar joints in transferring oct-of-plane shears is shown in Table 1, which lists the maximum shear stress in each wall.
(2) While the shear capacity of the mortar joints alone is con-sidered sufficient to resist the out-of-plane shear loads at the bottoms of masonry walls, an additional factor of safety is available through frictional resistance.
The dead weight of the wall produces enough friction to resist the shears even if the mortar joint was completely cracked.
Table 2 lists the factors of safety between out-of-plan?
shear loads and the available frictional resistance for each wall.
Also requested in action item #8 is a listing of the maximum tensile stresses normal to the bed joint due to out-of-plane loads for each wall.
Table 3 provides this information.
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- A ACTION ITEM NO. 15 The licensee will provide an assessment of the possible impact on wall capacity / behavior for neglect 4.ng the presence of an undefined amount of reinforcement in the masonry and assuming the walls as unreinforced in the analysis by 08/15/81.
RESPONSE
Computech Engineering Services Report No. R553.04,
" Assessment of Reinforcement on the Capacity and Behavior of Masonry Walls", is offered in response to Action Item No. 15.
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ACTION ITEM NO.
1_8_
With regard to Wall 19, the licensee shall evaluate out-of-plane drift effects resulting from the addition of knee braces at the top, provide the information for URC review by 08/15/81.
RESPONSE
Computec Engineering Services Report No. R553.03, "Out-of-Plane Drift Effect on Wall 19/9"j is offered in response to Action Item No. 18.
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4 ACTION ITEM NO. 19 With regard to..- I 5-5, the licensee shall clarify the applicable piping loads, manner of attachment, and their use in analysis by 08/15/81.
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Response to Action Item #19 to develop pipe loads on masonry walls and The assumptions used the method of their inclusion in the masonry wall analyses have been reviewed and are described below.
Piping loads consist primarily of dead loads and horizontal' SSE loads.
All pipe loads were included on a tabulation shown to the NRC staff during the June 9, 1981 audit.
The dead loads in the tabulation are those that would be trans-ferred to the masonry walls if the pipes were grouted into the However,most of the pipes penetrating masonry walls have walls.
in the walls.
The masonry gaps between the pipes and the sleeves include piping dead loads if the pipes were wall analysis did not Dead loads from grouted-in pipes were included in the sleeved.
masonry wall analyses when the dead loads were significant (greater than 100 lbs).
Horizontal SSE pipe loads are those that would be transferred to the masonry walls if the pipes were grouted into the walls.
Since the pipes may deflect significantly in the horizontal direction during an SSE, the pipes may contact the masonry walls Therefore, the horizontal SSE even when the pipes are sleeved.
pipe loads were always included in the wall analyses, regardless of the grouting condition.
In cases when the pipe stress analysis indicated a need for a pipe support at a block wall, a pipe support anchored to rein-forced concrete was designed and installed.
Wall #5-5 is a typical case which did not include piping dead Horizontal loads due to the gap between the pipes and the wall.
SSE loads, for which wall #5-5 was analyzed, will not be resisted attached to an ad-by the masonry wall because a pipe support, jacent reinforced concrete wall, has been installed.
110/20 J
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ACTION ITEM NO. 20 F
The licensee shall revise the criteria submitted on 11/14/81 to reflect the agreements reached in this meeting including deletions of positions on reinforced masonry and alternate I
acceptance criteria by 08/15/81.
i
RESPONSE
I The " Criteria for the Re-evaluation of Concrete Masonry I
Walls for Point Beach Nuclear Plant" has been revised to l
reflect the agreements reached in the June 9, 1981 NRC staff meeting.
The justification for the criteria has also I
been revised accordingly.
Revised copies are attached.
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APPE!1 DIX B CRITERIA FOR Tile RE-EVALUATIO!i OF COtJCRETE MASO!!RY WALLS For Point Beach fluclear Plant Revision 1, August 15, 1981 l
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CONTENTS Page I
1.0 GENERAL..............................................
1 1.1 Purpose.........................................
1 1.2 Scope...........................................
1 2.0 GOVERNING CODES......................................
1 3.0 LOADS AND LOAD COMDINATIONS..........................
1 3.1 Se rv ice Load Cond i t ions.........................
2 3.2 Factored Load Conditions........................
2 3.3 Definition of Terms.............................
2 4.0 MATERIALS............................................
2 4.1 Concrete Masonry Units..........................
3 4.2 Mortar..........................................
3 4.3 Grout...........................................
4.4 Horizontal Joint Reinforcing....................
3 3
4.5 Bar Reinforcement...............................
3 4.6 Pacing Brick....................................
3 5.0 DESIGN ALLOWABLES....................................
3 5.1 Stresses........................................
4 5.2 Damping.........................................
4 6.0 ANALYSIS AND DESIGN..................................
6.1 Structural Response of Unreinforced Masonry Walls 4
6 6.2 Accelerations...................................
6 6.3 Interstory Drift Effects........................
6 6.4 In Plane Effects................................
7 6.5 Out of Plane Effects 7
6.6 Equipment 6.7 Distribution of Concentrated Out of Plane Loads..
7 7.0 (Deleted) 8.0 ChITERIA FOR CVALUATION OF MASONRY BLOC KOUTS..........
8 8
8.1 Blockouts Spanning Horizontally..................
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CRITERIA FOR TIIE PE-EVALUATION OF CONCRETE MASONRY WALLS FOR TIIE POINT BEACll NUCLEAR PLANT 1.0 GENERAL 1.1 Purposc These criteria are provided to establish design re-guirements and criteria for use in re-evaluating the structural adequacy of masonry walls as required by URC IE Bulletin 80-11, Masonry Wall Design, dated May 8, 1980.
1.2 Scope The re-evaluation shall determine whether the masonry walls will perform their intended function under loads and load combinations specified herein.
Masonry walls not supporting safety systems but whose collapse could result in the ioss of required function of safety re-lated equipment or systems shall be evaluated to demon-strate that an SSE, accident or tornado load will not cause failure to the extent that function of safety rela ted items is impaired.
Verification of wall adequacy shall take into account support condition, global response of wall, and local transfer of load.
Evaluation of anchor bolts and embedments are not considered to be within the scope of IE Bulletin 80-11.
2.0 GOVERNING CODES For the purposes of re-evaluation, the American Concrete Institute " Building Code Requirements for Concrete Masonry Structures" (ACI 531-79) is used except as noted herein.
3.0 LOADS AN? LOAD COMBINATIONS The walls shall be evaluated for the following loads.
3.1 Service Load Conditions D+R+T+E R3/6
T_......v._._.._..._.
3.2 Factored Load Conditions 1.25 D + 1.0R + 1.25E + 1.0P
- 1. 2 5D + 1. 2 5T + 1. 2 5E + 1. 0P 1.0D + 1.0R + 1.0E' + 1.0P 1.0D + 1.0T + 1.0E' + 1.0P
- 1. 0D + 1. 0T + 1. 0W '
3.3 Definition of Terms D - Dead loads or their related internal moments'and forces including any permanent equipment loads.
R - Pipe reactions during normal operating or shutdown conditions, based on the most critical transient or steady-state conditions.
T - Thermal effects and loads during normal operating or shutdown conditions, based on the most critical.
transient or steady-state conditions.
E - Loads generated by the operating basis earthquake.
E'- Loads generated by the safe shutdown earthquake.
W'- Loads generated by the tornado specified for the plant (due to depressurization).
P - Force or pressure due to pipe rupture.
i 4.0 MATERIALS The project specifications indicate that materials used for the performance of the work were originally specified to l
meet the following requirements.
4.1 Concrete Masonry Units l
I Hollow Concrete Blocks:
ASTM C-90 Grade U-l with linear shrinkage limited to 0.05 percent.
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4.2 Mortar Mortar and mortar materials: ASTM C -270 Type N.
4.3 Grout Materials proportioned to produce a grout having a minimum compressive strength of 2500 psi at 28 days.
4.4 llorizontal Joint Reinforcing "Du-ro-wal" standard truss type (or equal).
4.5 Bar Reinforcement ASTM Designation A15, intermediate grade, deformed bars por ASTM 305.
4.6 Facing Brick ASTM designation C216-6 5, Grade SW, Type FDX.
1 5.0 DESIGN ALLOUABLCS 5.1 Stresses Allowable stresses for the loads and load com-binations given in Section 3.1 will be as given i
l in this section based on the following compres-sive strengths or as amended by action item #1 of the June 9, 1981 NRC staff meeting:
Hollow Concrete Ugits f'
= 1000 psi Hollow Concrete Units f'm = 1000 psi Grouted Solid Solid Concrete Units f'm = 1000 psi Stresses in the reinforcement and masonry shall be computed using working stress procedures.
The allowable stresses for service loads given in-Section 3.1 shall be the S values given in Table 1 for unreinforced masonry.
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I For walls subjected to thermal effects the allow-able stress shall be 1.3 times the S values given in Table 1.
The allowable stresses for the fac-tored loads given in Section 3.2 shall be the U values given in Table 1.
I 5.2 Damping The damping values to be used shall be as follows:
Unreinforced walls 2% - OBE 4% - SSE 6.0 ANALYSIS AND DESIGN 6.1 Structural Response of Unreinforced Masonry Walls 6.1.1 Out of Plane Effects i
1.
All walls shall be modeled as a plate with appropriate boundary conditions.
For a multi-mode analysis, the modal i
responses shall be combined using the square root of the sum of the squares of the first five modes, a
2.
The maximum moment and stress in block-4 outa shall be determined by applying a uniform load to the beam.
The maximum value of the uniform load shall be mass times acceleration taken from the response spectrum curve at the appropriate fre-quency for the fundamental mode.
i 3.
Where multi-wythe walls exist, no credit sha:.1 be taken for collar joints.
Multi-vythe walls shall be analyzed as a series of independent single wythe walls.
Verification of the conservatism of this assumption 1
i is provided in.the response to action item #5 of the June 9, 1981 NRC staff l
meeting.
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...... ~.........
6.1.2 Frequency Variations in Out of Plane i
Uncertainties in structural frequencies of the masonry wall resulting from variations in mass, modulus of elasticity, material and section prop-erties shall be taken into account by varying the modulus of elasticity as follows:
Ungrouted walls - 1000f',to 600f',
Grouted or Solid Walls
- 1200f'm to 800f'm If the wall frequency using the lower value of E is on the higher frequency side of the peaks of the response spectrum, it is considered conser-iative to use the lower value of E.
If the wall frequency using the higher value of E is on the lower frequency side of the peaks of the response spectrum, it is considered conservative to use the higher value of E.
If the frequencies of the wall straddel the peaks of the response spectrum i
when using the higher and lower values of E, the peak of the response spectrum shall be used.
4 4
6.1.3 In Plane and Out of Plane Effects Provided both the allowable stress criteria for out of plane effects and the in plane stress or strain criteria are satisfied, the walls shall be i
considered to satisfy the re-evaluation criteria.
6.1.4 Stress Calculations f
All stress calculations shall be performed by conventional methods prescribed by the Working 3
Stress Design method.
1 I
i R3/6,
6.2 Accelerations For a wall spanning between two floors, the envelope of the spectra for the floor above and below shall 4
be used to determine the stresses in the walls.
6.3 Interstory Drift Effects The magnitude of interstory drift effects shall be determined from the original dynamic analysis.
6.4 In Plane Ef fects If a masonry wall is a load bearing structural ele-ment shear stresses shall be evaluated and cornpared with the allowable stresses of Tables 1 and 2.
If the wall is an infill panel or non-load bearir.g element, shear stresses resulting from interstory drift effects will not be calculated.
In this case, the imposed interstory deflections of Sec. 6.4 shall be compared to the displacements calculated from the following permissible strains for service loads.
For factored loads, the strains shall be multiplied by 1.67.
The deflections shall be calculated by multi-plying the permissible strain by the wall height.
III Unconfined Walls Yu = 0.0001 (2)
Confined Walls Yc = 0.0008 Notes: (1) An unconfined wall is attached on one vertical boundary and its base.
(2) A confined wall is attached in one of the following ways:
(a) On all four sides.
i (b) On the top and bottom of the wall.
(c) On the top, bottom and one vertical side of the wall.
(d) On the bottom and two vertical sides of the wall.
(3) A discussion on the applicability of the above strain values is R3/6.
provided in the response to action action item #o of the June 9, 1981 NRC staff meeting.
If an infill panel or non-load bearing element is sub-jected to both interstory drift effects and shear stresses due to inplane loads from equipment or piping, the following criteria shall apply.
actual inplane actual inter-shear stress story deflection
+
1 allowable inplane allovable inter-shear stress story deflection A more refined analysis may be performed if necessary.
6.5 Out cf Plane Effects out of plane effects have been addressed in the response to action item #11 of the June 9, 1981 NRC staff meeting.
6.6 Equipment If the total weight of attached equipment is less than 100 lbs., the effect of the equipment on the wall shall be neglected.
If the total weight of the equipment is greater than 100 lbs., the mass of the equipment shall be added to that of the wall in calculating the fre-quency of the wall.
Stresses resulting from each piece of equipment weigh-ing more than 100 lbs. shall be combined with the wall inertia loads using the absolute sum method or the SRSS method provided the use of the latter is justified.
Stresses resulting from the equipment shall be calculated by applying a static load consisting of the weight of equipment multiplied by the peak acceleration of the re-sponse spectrum for the floor level above the wall if the frequency of the equipment is unknown.
If tne frequency of the equipment is known, it may be used to determine the static load.
6.7 Distribution of Concentrated Out of Plane Loads 6.7.1 Plate or Two Way Action For plate action, local moments and stresses under a concentrated load shall be determined numerically using a finite element ana!
.is.
1 R3/6.
6.7.2 Localized Block Pullout For a concentrated load, block pullout shall be checked using the allowable values for unrein-forced shear walls in Table 1.
7.0 (Deleted) 8.0 CRITERIA FOR EVALUATION OF MASONRY BLOCKOUTS 8.1 Blockouts spanning horizontally:
For the evaluation of blockouts spanning horizontally, the provisions of Section 6.0 will be used.
R3-6
... - =
.m..
Table 1:
Allowable Stresses in Unreinforced Masonry S
U Allowable Maximum Allowable Maximum Description (psi)
(psi)
(psi)
.(psi)
Compressive Axial (1) 0.20f',
200 0.44f'm 440 Flexural 0.33f',
330 0.85f'm 850 Bearing On full area 0.25f'm 250 0.62f'm -
620 On one-third area or less 0.30f',
300 C.73f',
750 Shear Flexural (2) 1.1 /f'm 34.8 1.7 /f',
53.8 members Shear walls (2) 0.9 /f'm 28.5 1.35 /f'm 42.7 Tension Normal to bed joints Hollow units 0.5 Vm 13.7 0.67 Vm 18.3 o
o Solid cr groutei 1.0 Vm 27.4 1.33 Vm 36.5 o
o Parallel to bed joints Hollow units 1.0 Vm 27.4
- 1. 6 7 g/m 45.7 g
g Solid or grouted 1.5 /m 41.1
'5
/m 68.5 o
g Grout Core 2.5 /f'c 4.2 /f'c Notes to Table 1:
1 _ (tut)3),
h (1)
These values should be multiplied by
(
(2)
Use net bedded area with these stresses.
R3-6
- s. =t.
- .. 1:.::: z : = :.:....
^
j 1
l APPENDIX C
,i
)
I i
+
r 4
I I
i, i
JUSTIFICATION FOR THE I
CRITERIA POR THE RE< EVALUATION i
l
}
OF CONCRETE MASONRY WALLS
\\
FOR i
POINT BEACH NUCLEAR PLANT I
Revision I, AugoS+ /5, /981 i
i i
l 1
?
e 4
h 1
1 l
I 1
l.
1 g
1 1
u I
- i 1
1
.,-.,,,,,..,n,,.,nn-n,
-c.
-n.n -.--....
.. ~. - -.... - -.,. _. - -
_ ~.. _ _
4 CONTENTS Page 1
1.0 GENERAL.. '......................
GOVERNING CODES...................?.
1 7
2.0 2
3.0 LOADS AND LOAD COMBINATIONS..............
2 4.0 MATERIALS.......................
2 5.0 DESIGN ALLOWABLES...................
2 5.1 ALLOWABLE STRESSES................
25 5.2 DAMPING.....................
25 6.0 ANALYSIS AND DESIGN..................
25 6.1 STRUCTURAL RESPONSE OF UNREINFORCED WALLS EB 6.2 ACCELERATIONS 28
- 6. 4 IN PLANE EFFECTS.................
34 6.6 EQUIPMENT 34 6.7 DISTRIBUTION OF CONCENTRATED OUT OF PLANE LOADS 7.0 (Ocleted) i l
l l
i l
l l
l l
l l
n.
~.
JUSilflCATION FOR THE CRITfRI A FOR THE RE-EVALUATION OF CONCRETE KASONRY WALLS 1.0 GENERAL The specification is provided to establish. design requirements and criteria for use in re-evaluating the structural adequacy of concrete block Direct reference to building code criteria walls in nuclear power plants.
was not used for the following reasons:
Jn of the magnitude o? seismic loads in building
- 1) The definit':
In codes is different than that used in nuclear power plants.
building codes damping, ductility, site effects and framing systems are factored into the seismic design base shear force.
In nuclear power plants these factors are considered explicitly in the design of components.
Building code allowable stresses do not consider two levels of 2) earthquake ground motion and the magnitude of the ground motion included in the building code design spectrum is not explicit.
Factors such as damping, analysis procedures, effect of attached 3) egoipment, two levels of allowable stresses, operability and frequency variations are not considered in building codes.
I Thus the specification was developed to address the problems unique to nuclear power plants.
2.0 GOVERNING CODES As noted in Sec. 1 the specification covers most of the factors unique Items not explicitly covered by the specification to nuclear power plants.
will be governed by the American Concrete Institute " Building Code ACI-531(29).
This code Requirements for Concrete Masonry Structures".
incorporates most of the recent research data available on concrete masonry.
1
~ -
3.0 LOADS AND COMBINATIONS These are consistent with the original structoral design criteria for the Point Beach plant.
4.0 MATERIALS materials The project specifications indicate that used for the performance of the work were originally the requirements given in this section.
specified to meet 5.0 DESIGN ALLOWABLES 1
The design allowable stresses given in Table and for are based on f'm the prism compressive strengtha ma the mortar compressive strength.
The mortar compressive strength is baseo an t
the minimum specified compressive strength of ASTM C-270.
t The concrete block unit compressive strength is based on the applicable ASTM Standard - ASTM C-90 for hollow units.
The prism compressive strength f'., is based on the 531-79.
This specified values given in Table 4-3 of ACI based on Table provides a conservative estimate of f'm the mortar and concrete block unit compressive strengths.
The minimun ASTM specified values of these variables were used in determining the conservative estimate of f',.
5.1 ALLOWABLE STRESSES The justification for the allowable stresses of i
Table 1 follows.
2
. -. -...... ~. -.... -.
....-.-.w (Unreinforced) 5.1.1
?XIAL COMPRESSION The following discussion of test results has been extracted from the commen'.ary to the N.CMA Specification for the Design anc Cons of Load Bearing Concrete Masonry.
The objective was to develop reasonable and safe engineering desi criteria for nonreinforced concrete masonry based on all existing data.
A review in 1967 of the compilation of all available test data on compres-sive strength of concrete masonry walls did not, according to some From a suitable relationship between wall strength and slenderness ratio.
a more recent analysis, it was noted in many of the 418 individual piec of data that either the masonry units or mortar, or in some cases, bot units and mortar, did not comply with the minimum strength requirdm established for the materials permitted for use in " Engineered Concre Accordingly, it was decided to re-examine the data, Masonry" construction.
discarding all tests which included materials that did not comply with the following minimum requirements:
Compressive Strength _
Ma terial 1000 psi Solid units 600 psi (gross)
Hollow units 700 psi Mortar Also eliminated from the new correlatior were walls d to ratio of less than 6; walls with h/t ratio less than 6 were considere For evaluation of slenderness reduction be in the category of " prisms."
The data that was available criteria, only axially loaded walls were used.
consisted of tests on 159 axially loaded walls with h/t ratio rangin With this as a starting point, the data were analyzed h3
, between 6 and 18. assuming that the parabolic slenderness is valid.
Basic equation used to evaluate the test data was:
l e
3 l
~ ^ ^ - -
f h
(I)
C, f' (1 - (4ot) )
3$t
=
f (2) test C,x S.F.
=
f' (1 - (4 t)3)
(3)
K C, x S.F.
=
where
= Assumed masonry strength, net area, based on strength f'
of units
= Net area compressive strength of panel f test S.F.
= Safety factor C,
= Strength reduction coefficient h
= Height of specimen, inches
= Thickness of specimen, inches t
Net area used in the above formulae is net area of the masonry, and In the evaluatior.,
does not distinguish 'between type of mortar bedding.
mortar strength was assumed to be constant and was not considered as a significant influence on wall strength.
It was detennined that the objective of reasonable and safe criteria would be met if 90% of the "K" values were greater than the K value Accordingly, the K i
selected and gave a minimum safety factor of 3.
values were listed in ascending order and the value satisfying the above conditions was K =.610 for the 159 tests as seen from i
Therefore, from equation (3):
l 1
4
- " ~
,...w.._
C x 5.F.
=K g
= 0.610 C, x 3 0.610 = 0.205 C
=
g This value, 0.205, agrees very closely with the coefficient 0.20 i
which had been used for a number of years with reinforced masonry des An analysis of the safety factors present with the formula:
f, 0.205 f, (1-(4$,',3)
=
indicates the following:
Safety factor great _r than 3 is availeble in 93;; of the tests; greater than 4 in 51% of the tests; greater than 5 in 15% of the tests and grea.ter than 6 in 5% of the tests.
l
.. s.
' Based on fortu1: (2), "K" f actors were es1culated for all of the specimens as listed in the following tabic:
test TABLE 3 Walls t
Concretc Masonry Units i
Mortar
- Strength,
/
- Strength, Percent psi, net Str.,
psi, net
. "./
Ref.
Solid arca f',
psi psi Bedding h/t feest f
K S.T.
1 63 1160 9SO 1180 Full 6.0 750. 97S
.798 3.83
~
63 1160 930 1180 Full 6.0 685 978
.701
'3. 4 9 l 63 1160 980
' 1160 FS 6.0 670 978
.686 3.42 63 1160 980 903 FS 6.0 555 978
.565 2.83 63 1200 1000 1230 Full 6.0 C60 995
.863 4.30*
63 1200 1000 730 Full 6.0 625 995
.627 3.12 63 1200 1000 960 FS
' 6.0 580 995
.582 2.89 63 1200 1000 780 FS 6.0 650 995
.652 3.25I 63 1320 1060 880 Full 6.0 1310 1055 1.050 5.25 63 1320 1060 S10 Full 6.0 970 1055
.918 4.58j 63 1320 1060 S10 FS 6.0 780 1055
.738 3.69 ;
63 1160 980
.1080 Full 6.0 800 978
.818 4.0S I 63 1160
- 980 10SO Full 6.0 670 978
.686 3.42i 63 1810 1275 1270 Full 6.0 940 1270
.739 3.67 1 3
940 1270
.739 3.67!
! 6.0, 63 1810 1275 11270 Full 63 1505 1150 1670 Full I 6.0 825 1145
.719 3.60
- 63 1505 1150 1670 Full l 6.0 820 l'.45
.715 3.57l 63 1240 1020 980 Full ! 6.0 1010 1015
.993 4.95 !
63 1240 1020 980 Full 6.0 870 1015
.856 4.26i 63 1720 1230 880 Full 6.0 1035 1225
.844 4.21 i 63 1720 1230 I 880 Full, 6.0 940 1225
.766 3.81 :
63 1380 1090 1730 Full I 6.0 1000 3085
.920 4.5S '
63 1380 1090
.1730 Full l 6.0 1010 1055
.930 4.63 I
145c 1257 1.152 5.75 l 6.0 63 1780 1262 1870 Full 6.0 1570 1257 1.24S 6.22 63 1780 1262
'1870 Full 43 3300 1790 1230 Full ! e.0 1560 1782
.574 4.36 43
- 3300 1790 1230 Fuli j 6.0 1730 17S2
.969. 4.84.
70 1645 1208 1140 Tu)1 j 6.0 1000 2200
.830 4.15 70 1645 120L 11140 Full 6.0 1220 1200 1.013 5.05 5
L8 63 509 458 (3140 Full 6.0 303 455
.664 3.30
- GJ 509 458 11610 Full 6.C 295 455
.646 3.21 *
(
63 509 45B l000 1 ell j 6.0 295 455
.646 3.21 I
I 63 840 756 3140 Full i 6.0 3r 753
.706 3.52:
I 63 S40 756
'1630 Full i, 6. 0 540 753
.716 3.58 I
63-840 756 l1060 Full j 6.0 505 753
.670 3.33 63 875 783 13140 Fu]1 ; 6.0 13S 785
.55B 2.79; 6
- .*}.
- .
l U:32*
Prt" Cor. r_ 0 "n c ar ' Wit:
l l
l 5:rcrm.:h.
~
Strength.
Percent psi, ne:
' Str.,
psi, nc t fd C 1*
S.F.
Ref.
Solid r.r c a fA, psi psi Ledding h/t f e. r. t--
t
-_w.
S 63 675 7S8 1610 Ful) 6.0 430 785
.547 2.74 i 63 875 7ES 1050 full 6.0 500 7ES
.637 3.17 63 10SO 940 3140 Full 6.0 605 936
.646 1.22 63 10S0 940 1610 Full 6.0 715 936
.763 3 S1 63 1030 960 1060 Full 6.0 765 936
.817 4.07 63 1230 1015 3140 Full 6.0 1160 1010 1.146 5.70 63 1230 1015 1610 Full 6.0 1000 1010
.988 4.92 63 1250 1015 2060 Full 6.0 1110 1010 1.097 5.46 63 1410 1105 3140 Full
,6.0 1140 1100 1.030 5.16 63 1410 1105 1610 Full 6.0 955 1100
.893 4.45 63 1410 1105 1060 Full 6.0 1030 1100
.935 4.66 63 1520 1157 c3140 Full 6.0 660 1152
.572 2.85 63 1520 1157 1610 Full 6.0 740 1152
.642 L.20 63 1520 1157 47S0 Full 6.0 830 1152
.719 3.58 63 1860 1255 3140 Full j6.0 1476 1290 1.143 5.70 l 63 1860 1295 1610 Full 16.0 1539 1290 1.192 5.94
.060 Full 6.0 1365 1290 1.05S 5.27' 63 1860 1295 63 2510 155*.
3140 Full 6.0 3693 1550 1.096 5.47 63 3510 1554 1610 Fu]1 6.0 1365 1550
.8B1 4.39 63 2510 155!.
1060 Full 6.0 1325 1550
.856 4.27 l 63 3030 1710 3140 Full 6.0 2222 1705 1.304 6.50 l g
I 16]O Full 6.0 2222 1705 1.304 6.50 3030 1710 63 3030 1730 1060 Full
'6.0 1984 1705 1.164 5.80 63 l
63 3740 lo23 3140 Fall 6.0 1857 1918
.969 4.82 63 3740 1923 1610 Tull 6.0 2523 1918 1.316 6.56 63 3740 1923
!.700 Full 6.0 2317 1918 1.209 6.03 l 63 6640 2400 3140 Full 6.0 3587 2392 1.499 7.48 :
63 6640 2400
.1610 Full 6.0 3856 2392 1.612 S.04 j 63 6640 2400 l4780 Full 6.0 5031 2392 2.102 10.49 l 1
I 12**
100 1383 1: 57 2562 Full 7.0 1140 1254
.910 4.13 1 100 13SS I t. '.0 3017 Full 7.0 1358 1635
.830 4.57 l 100 1892 1853 2317 Full 7.0 1469 1846
.795 4.52 l 100 1923 1630 2153 Full 7.0 1394 1625
.858 4.20 100 250S 2390 242; Full 7.0 1947 2380
.817 4.56 100 2529 2630 2347 Full 7.0 2151 2620
.820 4.63 l 100 2545 2130 2143 Full 7.0 1930 2120
.909 4.17 l 207E 2210
.939 4.71 1 l7.0 100 2610 2220 3195 Fu13 7.0 IS32 2020
.905 3.?9 l 100 2678 2030 l2322 Full 100 4474 22]C 2792 Full 7.0 1310 2200
.621 4.10 i 100 4474 2540 ' 215'.
Full 7.0 2157 2530
.937 4.00 l l
l s
i reference s.cre deternir.ed fron pri:
tests in-l
- fE values from thic recul:s r.ultip12c6 by f actor of 1.2 j stead of ar..curied va]ue:.
7 cst I
o.
(
7 1
~.. -...
i!.a 3 h.y:r J )
- crtr.r Un l l t.
Concrete Ihsenry Units
- Strength, S t r cui,t h,
Percent psi, net Str.,
psi, net fE, psi psi Eedding h/t f
f f. C K
S.F.
t e r, t Ref.
Solid area i
5-62 2557 1556 1403 FS 9.0 1241 1540
.807 4.05 62 18S6 1305 1400 FS 9.0 1153 1290
.894 4.50 62 1999 1350 1400 FS 9.0 967 1335
.724 3.63 62 1499 1150 1400 FS 9.0 685 1135
.603 3.02 62 1934 1325 1400 Full 9.0 1354 1310 1.033 5.19 62 2305 1473 1400 FS 9.0 1096 1455
.752 3.75 62 2136 1405 1400 FS 9.0 1125 1390
.812 4.07 62 1773 126.
1400 FS 9.0 108S 1245
.873 4.38 62 1298 1049 1400 FS 19.0 85!.
1037
.823 4.14.
62 1241 2031 1400 FS' 9.0 6S5 1010
.678 3.41I 62 1612 1196 1400 FS 9.0 991 1180
.838 4.20l 4.33l 62 1805 1273 1400 FS 9.0 103S 1260
.864 62 1491 1146 140D FS 9.0 654 1133
. 7 5!.
3.78 j 62 1C23 944j1400 FS 9.0 629 933
.673 '3.35 62 1918 1318 11400 FS 9.0 1072 1302
.822 4.12 62 1169 985 1400
'FS 9.0 605 975
.621 3.12 45 2655 1598 1400 FS 9.0 989 1578
.626 3.15 I 62 1088 944 1400 FS 9.0 564 933
.604 3.03 i
701 1032
.678 3.41 l9.0 62 1290 1045.1400 FS 9.0 1104 1335
.826 4.16 62 1999 1350l1400 FS 62 1862 1296 1400 Full l9.0 1378+ 1280 1.075 5.44N 62 4
967 870 1400 Full j9.0 758 660
.881 4.42 62 1967 1338 1400 Full j9.0 1241 1320
.933 4.72 i
1463l!1400 1400 FS
' 9.3 1228 1450
.849 4.27 5
57 2280 1318 FS 9.3 836 1302
.642 3.23 l 67 1917 67 13S0 1090{1400 FS l 9.3 724 1078
.672 3.37!
67 1902 1312 1400 FS
' 9.3 1223 1300
.943 4.74 3.67l 67 1246 1023 1400 FS
- 9.3 739 1010
.731 4.3S 1193 1370
.871 j 9.3 57 20S7 1386
,1400 FS 9.3 129S 1370
.948 4.76 l 57 20S7 1386j S30
,FS g
l 57 23SS 1505[1400 FS
! 9.3 719 1485
.484 2.44 57 2385 1505 i 1400 FS l 9.3 789 14SS
.530 2.67 57 2385 1505i1400 FS
, 9.3 1105 1485
.743 3. 7!.,
57 2385 1505 ! 1400 FS i 9.3 1140 la85
.766 3.85 l 885 li?O
.756 3.79 l9.5 1
39 1590 1187 ; 1130 Fuli 9.5 1000 1170
.S53 4.28 39 1590 1187i 1030 Full 39 1718 1238,1070 Fu2) i 9.5 949 1220
.???
3.89 i
39 1718 1238'. 840 Full i 9.5 910 1220
.745 3.73 8
.5 l
l 8
w
' T/J...; f_(0:
Inu.;;
D13 e I'-r:rr Cen:n te "rr enr e Unit:
S t r e e r.t l.,
Streng. n, Str.,
psi, net Percent psi, net Ref.
Solid arca f',
psi psi Ecdding h/t f
IE. C E
S.F.
t e r. t 1
63 1159 985 11P.0 Full 14.3 683 940
.726 3.E2
~
63 1139 9G5 1440 Full 4.3 690 940
.734 3.66,
63 1159 985 1440 Full 14.3 738 940
.784 3.918 63 1159 9SS 1060 FS 14.3 532 940
.565 2.S2 63 1159 985 900 FS 14.3 563 940
.599 2.9S 63 1159 985 1920 FS 14.3 563 940
.599 2.98 63 1206 1020 1230 Full 14.3 738 974
.753 3.50 63 1206 1020 730 Full 14.3 683 974
.702 3.51 63 1206 1020 1130 Full 14.3 746 974
.765 3.53 63 1206 1020 960 FS 14.3 571 974
.586 2.54 !
I 63 1206.
1020 780 FS 14.3 603 974
.619 3.10 63 1206 1020 (1250 FS 14.3 595 974
.610 3.05 63 1317 1080 880 Full 14.3 905 1030
.877 4.38 l
63 1317 1030 750 Full 14.3 1063 1030 1.030.
5.14 g
63 1317 1080 810 Full 14.3 929 1030
.901 4.49-63 1311 1050 1020 FS 14.3 714 1030
.692 3.45 63 1317 10C0 1020 FS 14.3
- 667, 1030
.647 3.23 63 1159 985 l1120 full 14.3 579 940
.616 3.078 63 1159 985 1150 Full 14.3 635 940
.675 3.37 63 1159 985 1080 Full 14.3 635 940
.675 3.37 1 1270 Full 14.3 873 1218
.717 3.54!
63 1810 1274 940 Full
,14.3 881 1216
.725 3.58l 63 1810 1274 63 1810 1274 1120 Full 14.3 817 1218
.671 3.32i 63 1506 1153 1380 Full 14.3 706 1100
.641 3.17!
63 1503 1153 1380 Full 14.3 746 1100
.677 3.34l 63 1508 1153 1670 Full 14.3 643 1100
.584 2.S8 !
63 1238 1025 fl920 Full 14.3 833 978
.851 4.24,
4.09 l!
63 1238 1025 980 Full 14.3 802 978
.819 4.16 L 1.
3 817 97S
.835 4
63 1238 1025 1280 Full 63 1714 1230 l 800 Full 14.3 1111 1172
.946 4.73!
63 1714 1230 800 Full.14.3 1127 1172
.959 4.79l 63 1714 1230 J 750 Fuli 14.3 1079 1172
.918 4.59 63 1381 1090 11730 Fu13 14.3 968 1040
.930 4.64 i 63 1381 1090 l2200 Full ;14.3 960 1040-.923
- 4. 61 l l
63 1774 1245 12100 Full !14.3 1240 1190 1.043 5.21 !
63 2253 1450 l1230 Full !14.3 936 1355
.675 3.42!
63 2253 1450 il270 full 14.3 920 1385
.664 3.37l 70 1643 1206 !11SO Full 14.3 507 1150
.701 3.55i 70 1643 1206 11300 Full l14.3 936 1150
.857 4.33' L
SS 1273 1040 11220 Full 114.3 727 5^3
.732 3.66l 55 1273 1040 {1220 Full l14.3 764 993
.770 3.S4 l 7
100 2900 1665 1475 Full ;15.0 1250 1565
.S01 3.93 4
-j -
r --
5 65 1 74.6 1250 1400 Full i18.0 1100 1135
.975 4.S7 a
65 1246 1015 1400 Full j]8.0 765 925
.850 4.25 65 1562 1175 l1400 Ful l l18.0 1203 1065 1.331 5.65 j l
9 t
(Unreinforced)
FLEXURAL COMPRESSION 5.1.2 It is assumed that masonry can develop 85% of its specified The recommended procedure for compressive st:ength at any section.
calculating the flexural strength of a section is the working stress procedure, which assumes a triangular distribution of strain.
For normal loads an allowable stress of 0.33 f' has a safety of 2.6 for the peak stress, which only exists at the extreme The fibre of the unit and has been used in practice for many years.
recomended value for factored loads also only exists at the extreme fibre and is the value recommended in the ATC-3-06 provisions.
(Unreinforced) 5.1.3 BEARINGTnese values for normal loads are taken directly from the ACI The value recommended for ' factored loads is the value code.
recomended in the ATC-3-06 provision.
5.1.4
( D e. l e. + e. d )
m a
10
5.1.5 SHEAR (Unreinforced)
INTRODUCTION The present literature on shear strength capability varies greatly on the approach used to determine acceptable values and to some extent, the controversey over these approaches and interpre-tation of the results.
Debate, on the applicability of model or full size tests and,the effects of monotonic versus cyclic loading further seems to complit, ate this resolution.
Much of the effort to define a permissible in-plane shear stress may be somewhat academic, in that the normal case for unreinforced walls being used in nuclear plant structures, the nature of the shear is one of being forced on the structural panel as a result of being confined by the building frame and not one of This depending on the panel to transmit building shear forces.
shear stresses and strains, forced drift or displacement results in but because of the complex interaction between the panel and the i
confining structural elements strain or displacement is a more meaningful index for qualifying the in-plane performance of the The area of in-plane strains is being addressed in another panel.
committee report.
The most extensive review on shear strength literature appears 2
to have been done by Mayes, et al, and published in Earthquake l
Engineering Research Center Report EERC No. 75-15 which was done for both brick and masonry block.
This report attempts to summarize some of the findings that appear to be pertinent towards defining permissible shear stress values that can be used for reevaluation of the non reinforced concrete masonry.
SUMMARY
The shear value of 0.9 y/((~providedbytheACI-531-79 code for reinforced masonry appear to be reasonable basis on which This value appears to to proceed with the reevaluation program.
conservatively bound the actual expected shear strength of ' concrete I
l 11
- -+
e A sunmary of several different sources for shear block masonry.
An increase in these stress-desion values is shown by Table 5.
allowable values for the re-evaluation program of 1.35 /f' for y
severe loading conditions appears warranted.
Any further increase at this time without further substantiation and review is not seen as advisable.
DISCUSSION A number of tests have been identified as being the primary basis for permissible shear stress values in both National Concrete Masonry Association (NCMA) " Specification for the Design and and the American Construction of Load-Bearing Concrete Masonry" ".5 Concrete Institute Standard " Building Code Requirements for Concrete Masonry Structures" (ACI-531-79) 2,2 No apparent tests are traceable to the origin of the Uniform Building Code (UBC) chaoter 24 on " Masonry."'
~
Those tests performed to substantiate the NCMA values are primarily performed by the National Bureau of Standards (NBS) on These full size (4 ft by 8 ft, and 8 ft by 8 ft) test panels.
18 within the tests were performed by Whittemore, et al and Fishburn The Whittemore tests were done, as usual in period 1939 to 1961.
that period, utilizing a hold down detail and thereby introducing s clamping or compressive stress within the assemblage. A number of studies have shown that compressive stresses affect the shear The Fishburn tests, utilize a racking strengtn significantly.
configuration with the testing being performed on the panel in its A load setting up principal tension original laid up position.
stress causing failure is an accepted measure of shear stress determination by the American Society of Testing Material for The test results from the above references used by brickwork.22 NCMA are shown on Table 6.
The principal tests that seem to formulate the ACI 531 basis are the tests performed on concrete masonry piers for Masonry These tests had a system
{
Research of Los Angeles, by Schneider.2:
for removing the compressive load on the spe:imen being loaded by
~'
shear and were set up to vary the a/d (M/Vd) ratio and measure this effect on a parametric basis.
The two predominant failure modes of'a masonry panel under shear are diagonal tension (causing a " splitting" failure) and shear bond (causing a " joint separation" failure) or some combination of these The theory behind these were elaborated on by Yokel two effects.
The parameter of normal stress and its effects on a shear et al.2' and Mayes
,2', has been 2
28 strength, which was also reviewed by Yokel demonstrated to be consequestial on the determination of actual This parameter is not identified, today, shear stress capability.
by any of the codes,6,s,is,is shown in Table 5.
z It is expected that under zero or small compressive loads the predominate shear failure will be by the shear bond mode of failu Tests which have been done with regard to the determination of.ioin as well as Hamid, separation were performed by Copeland and Saxer,27 These tests are, by their nature, extremely sensitive to et al.2' normal stress and consequently do relate the effects of normal stress This relationship is shown on Table S.
on permissable shear values.
It is of interest that there appears to be good correlation between these tests on the shear strength with zero normal stress.
The Applied Tect.nology Council (ATC) is presently reviewing a formulation for increasing the shear stress as a function of norma This formulation is developed to coincide with their present permissible shear stress of 12 psi and is consistent with the stress.
fundamental direction as a desi n code, forcing reinforcing for g
seismicly designed masonry structures.
As a practical matter, walls subject to. the conditions of confinement will experience large compressive loads - although Compressive loads for the most these are difficult to determine.
part, imparted by boundary conditions and behavior of the b If frame are ignored in the evaluation of the masonry panel.
these nornal stresses are added the shear resistance This implies a conservatism on the allowable shear increased.
value when one assumes this value as chosen on the 13
~...-
~..
On this basis, and tne tests results discusscd, tr.c shearvalueof0.9,[fyriosenbytheACIcodeappearstobejustified normal stress.
d and should be established as a reasonable basis by which to procee with the re-evaluation.
Out of plane, or so called flexural shear is defined by the code as equalling 1.1 /f[7" The derivation of this value is analogous to
~
be permissible shear value of concrete, disregarding any reinforce y
is no ment, of 1.1,/' Although this is somewhate different (there i tension steel by which to determine the appropriate j distance), actual value is a mute point since tension will be the critical l member. value for determining out-of-plane acceptability of a flexura Because of the nature of the stresses, however, and the various concerns with regard to the correctness of interpretation of the actual effects on boundary conditions as well as such conditions as: lack mortar properties; absorbtivity of the mortar; confinement or f of it on the test specimen during test; arrangement and effect o actual load, it does not seem warranted to increase these stresses f'). This value is consistent beyond a value of 1.35 /f[~(1.5 x 0.9 y ll test with an adequate margin of safety for both the full panel wa Any specimens referenced and the shear bond values observed by t d additional increase in the shear stress values for nonre his masonry under extreme environmental loads is not recommende time. 4 f4
.~ _., T/.I.:,E SUFF.ARY - UN0 ROUTED MASONRY Remarks Shear Stress Date Source 0.9 % 4 34 M/VD 3 1 79 (1) ACI-531 Type M or S Motor 34 (1) NMCA 79 Type N Mortar 23 Based on NBS tests (circa 1939-1961) Type M or S/N Mortar 12/10* 79
- 12 psi for solid units (1) UBC Lightweight units limited 12 I
78 to 85 percent shear value (1) ATC 3-06
- being proposed for compressis
- 12 + 0.20&Ez, 30 stresses between 0 and 120 pr
~ 1.0 h 4 35 s/1 g 1 May be increased by 0.20 c 16 Proposed (1) Masonry (due to dead load) Society Ultimate value based on IO 76 + 1.070E Hamid, et al 79 type S mertar 64 70 + (fitted) Ultimate value based on 2630 compressive mortar Copeland/Saxen strength (1) Values based on inspected workmanship
- c = compressive acress.
i$ ~
TABLE 6 RACKING TEST DATA--NONREINFORCED CONCRETE MASONRY WAL Ultimate Racking S.F. Mortar Load, psi, Net Construction Type Mortar Bedded Area Act./ Allow Ref. 8" Hollow Units N 66 2.87 7 N 58 2.52 7 N 57 2.48 7 6" 3-Core Hollow N 69 3.00 8 N 62 2.70 8 N 78 3.39 8 8" Hollow Units N 79 3.43 10 N 79 3.43 10 N 73 3.17 10 N 119 5.17 10 N 129 5.61 10 4.74 10 N 109 S 132 3.88 10 S 139 4.09 10 S 129 3.79 10 S 159 4.68 10 S 132 3.88 10 S 159 4.68 10 4-2-4 Cavity Wall M 103 3.03 9 of Hollow Units M 108 3.18 9 M 102 3.00 9 Avg = 3.65 Range = 2.48 - 5.61 h From Reference 5 t e llo =
LIST OT RIT:RE':CET FOR Sli2AR (l'nreinf orcedi Mayes and Clough, " Literature Survey - Compressive, Tensile, Bond and S I Strength of Masonry," Earthquake Engineering Research Center, University of California, 1975. ACI Standard, " Building Code Requirements for Concrete Masonry Structures, 2 (ACI 531-79). Concentary on " Building Code Requirements for Concrete Masonry Structu 3 (ACI 531-79). ' " Specification for the Derign and Construction of Load-Bearing Concrete Masonry" - NCMA - 1979. Research Data and Discussion Relating to " Specification for the Design 5 970. and Construction of Load Bearing Concrete Masonry" - NCMA - 1 Uniform Building Code, Chapter 24 " Masonry" - 1979. 0 Stang, and Parseas " Structural Properties of Six nasonry Wall Con-38. 7 structions," Building Materials and Structures Report No. S., NBS - 19 Whittemore, Whittemore, Stang, and Parsons " Structural Propert 8 National Concrete Masonry Association," Euilding Materials and Structures Report. i i Whittemore, Stang, and Parsons, " Structural Properties of Concrete Block Wall Construction" Building Materials and Structures Report 21, NBS 1939. 9 Fishburn, "Ef fect of Motar Strength and Strength of Unit on the Strength 10 of Concrete Masonry Walls," Monograph 36, NBS, 1961. hd ASTM Standard Specification for Brick and Applicable Standard Testing Me 11 for Units and Masonry Assemblages - May 1975. i Schneider, " Shear in Concrete Masonry Piers," California State Polytechn College, Pomona, California. l f Yokel and Fattal " Failure Hypothesis for Masonry Shear Walls" - Journal I the Structural Division, March 1976. 14 "A State of the Art Review - Masonry Design Criteria" - Computech - 1980 l " Tentative Provisions for the Development of Seismic Regulations - Applied Technology Council Chapter 12 A - ATC 3-06-1978. The Masonry Society Standard Building Code Requirements for Masonry Construction, First Draft. Copeland and Saxer, " Tests of Structural Bond of Masonry Mortars 17 Block" - Journal of the Structural Division - November 1964. " Shear Strength of Concrete Masonry Hamid, Drysdale, and Heidebrecht, 18 Joints," Journal of the Structural Division - July 1979. o l 17
5.1.6 TENSION (Unreinforced) Normal to the Bed Joint A. A summary of the static monotonic tests performed to determine code allowable stress for tension normal to the bed joint was given in the NCMA Specifications. Stresses (or tension in flexure are related to the type of mortar Research used to arrive at and the type of unit (hollow or solid). I allowable stresses for tension in flexure in the veritcal span (i.e. tension perpendicular to the bed joints) consisted of 27 flexural These tests of uniformly-loaded single-wythe walls of hollow units. Table 7 nonotonic tests were made in accordance with ASTM E 72. summarizes the test results. From Table 7 the average, modulus of rupture for walls built For Type N mortar, with Types M and S mortar is 93 psi on net area. Applying a safety factor of four (4) to these the value is 54 psi. values results in allowable stresses for hollow units as follo Allowable Tension in Flexure Mortar Type 23 psi M&S 16 psi N l These values are consistent with those published in the 1970 l ACI Committee 531 Report and which have been only slightly altere in ACI 531-79 Code. Based upon these tests the minimum factors of safey for each mortar type are: Factor of Safety Mortar Type 3.87 M 2.60 S 2.81 N To establish allowable tensile stresses for walls of sol These walls, units, the 8-inch composite walls in Table 8 were used. l composed of 4-inch concrete brick and 4-inch hollow block, were greater than 75% solid, and thus were evaluated as solid masonry 18 l i
Modulus of rupture (9.oss area) for these walls construction. averaged 157 psi, giving an allowable i, tress of 39 psi when a saf e The composite wall tests in Table 8 used Type facter of 4 is applied. To establish allowable stresses for solid units with Type N mortar, the mortar influence established previously for hollow units 5 mortar. was used: E : E ; f = 27 psi 16 f The minimum factor of safety for these tests for Type 5 mortar was Recent dynamic tests have been performed at Berkeley and the 2.33. of tension obtained at cracking at the mid-height of the walls are as 13 psi; 20 psi; 23 psi; 27. psi. follows: The recommended values have a factor of safety of 2.8 with resp to the lower bound of the static tests for the unfacto towards the lower limit of the initiation of cracking for the dynam An increase of 1.67 appeared reasonable for factored loads In accordence wdh the June 9, /9N N AC tests. w;ll bc u sed. on the static tests. fe<Aor of I33 S+aff m e c +in3, an in crs a se \\ l 19 e
TABLE 7 TLEXURAL STRENGTH-SIMOLE D.'TP.E W.I.LS OF HOLLOU UNI._ -- UNIF0F': LOAD-YERTICAL SPAN Mortar Type l Proportion Medulus of Rupture Reference ASn! C 270 psi, Ket Area 110 to M NOIA 108 M 10 102 M 10 97 M NCR 95 M NCMA 94 S NCMA 91 M NCh% M ,89 4 88 N 10 84 S NOR 83 S 10 81 S Na'A 75 5 Nom 69 S 4 67 (8 N 4 62 N 10 60 S 4 58 N 4 45 N 10 60 0 4 41 0 4 36 0 4 36 0 4 33 0 4 32 0 10 30 0 4 27 0 b e t. 2o (
TAELE B TLEXUF.C STE.E!!";T.-:, VEF.!!C/.1 EF/.!: CC:: F.ETE l'_'.! 0:'F.Y 1.*.'.'.LT FROM TESTS AT I;CMA la?.,0FATOFJ. Vall Modulus of Ruoture Uct Max. Net Mor:ar ASTM No=inal
- Unifor:
Section Gross l Bedded Mortar Thickness Ioad Mod lus Area, l
- Area, Type
- in.
psf. in 3/ft psi psi Honouythe Valls of Hollow Units M 8 85.15 80.97 61.74 BS.73 87.10 80.97 63.15 90.76 H 8 8 91.00 80.97 65.97 94.82 M M 8 103.35 80.97 74.93 107.69 S 8 62.40 80.97 45.24 69.47 S 8 72.15 80.97 52.31 i 75.18 S 12 183.3 164.64 57.11., 93.94 S 12 161.2
- 164.64 50.22 82.62 l
~ Co=posite Walls of Conerete Brick & Bollev CHU l S "- 8 222.3 103.82 161.16 180.67 5 8 219.7 103.82 159.29 178.55 5 8 187.2 78.16 135.72 202.09 l 5 8 228.8 103.82 165.88 185.95 5 8 218.4 78.16 158.34 235.77 S 8 223.6 78.16 162.11 241.38 S 12 171.6 139.83 53.46 103.55 S 12 150.8 139.83 46.98 91.00 S 12 156.0 139.83 I 48.60 94.14 S 12 213.2 139.83 66.42 128.66 Cavity Ualls l 5 10 98.8 .50.36 15S.62 165.55 ! S 10 156.0 50.36 250.44 261.38 5 10 88.4 48.16 141.91 154.83 ; 5 10 119.6 50.36 192.01 200.40 5 10 114.4 50.36 183.66 191.63 S lo l 109.2 4S.16 175.30 351.32 S 12(4-4-4) 145.6 I 50.36 233.73 243.9* 145.6 1 50.36 233.73 2'3.91 S 12(4-4-4) 135.2 77.80 127.3S 146.63 S 12(6-7-4) S 12(6-2-4) [ 119.6 77.00 112.68 129.70 I 2I M' : : ~.: :y;.c. Dy
- o.:*.:... s
.....u.-..'.6. e
Tension Parallel to Bed Joints B. Values for allowable tension in flexure for walls supported in the horizontal span are established by doubling the allowables in the While it is recognized that flexural tensile strength of vertical span. walls spanning horizontally is more a function of unit strength than Table mortar, it is conservative to use double the vertical span values. 9 lists a summary of all published tests and indicates an average safety factor of 5.3 for the 43 walls containing no joint reinforcement and 5.6 for the 15 walls containing joint reinforcement. It is important to note that the factor of safety for those walls loaded at the quarter points, Reference (6), have an average factor of safety of 2.02 with a minimum value of 1.22, while those loaded at the center had an average factor of safety of 6.08 with a minimum value of However, it should be noted that the values tested at the k points 3.59. were also tested at 15 days. The results associated with the early date of testing and the use of quarter point loading are "fficult to explain other than to state they are at variance with all other test results. An increase in the allowable by a factor of 1.67 is recommended for The committee believes that the recommended valu factored loads. be increased because of the larger factors of safety in the test results; however the value of 1.67 was chosen to be compatible with the incr other stresses for unreinforced masonry. The values recommended for stack bonded construction although at variance with current building codes (which allow zero) are thought t In a test program performed reasonable values for a reevaluation program. 1/3 the capacity by PCA(2) a horizontally spanning stack bonded wall had The recommended values are in of an equivalent wall laid in running bond. two-thirds of the value normal to i.e. accordance with this test data, the values recommended for parallel to the bed joint is equivalent to 1/3 the bed joint.
Reference:
- 3) Portland Cement Association, " Load Tests of Patterened Co f
Masonry Walls, " Trowel Talk an aid to Masonry Industry,1963.
TAILE 9 FLEXUPAL 5:3E::0!!!,1107.120NTAI. STA**, N0;.T.II :FCT.2E*.' C;;;;I.I!: ::A S C::71 U AL Ls Modulus l e, ~ * *
- of Rupture i
M'ortar I.ea di.: Are. esil ^
- //llou 7.e f.
a Construction Tvoe l Type ' psf i Ne: Monovyche 8", N Unifor= 127 1.2 4.13 4 Hollow. 3-Core N 136 141-4.41 4 N 127 132 4.13 4 N 169 176 5.50 ~4 N 173 180 5.63 4 0 123 128 4.00 4 158 ' 164 5.13 4 O Monovythe 8" N 149 155 4.84 4 Hollot:, Joint N J60 166 5.19 4 Reir.f. 0 16 i:.cc U 193 201 6.28 4 4.88 4 156 0 150 1B'6 ! 193 6.03 4 O 4 Honovyche 8" E 203 211 6.59 f 204 6.38 4 llollow Joint N 196 Reinf. G 8 in.cc 0 202 : 210 6.56 4 0 195 1 203 6.34 4 i I s ( 56! Monowy the-8" N 1/4 pt 5B 1.81 6 I Hollow N 38 l 30 1.22 6 ~ I N 61 l 63
- 1. 9 7..
6 l 62 1.94 6 60l N 69 71 2.22 6 N 93 ! 96 3.00 6 N ( l 4.72 26 i t 8" Monowythe M Center 199 ! 217 4.17 26 Hollou, 2-Core ' M 176 192 M~ 151 165 3.59 26 4-2-4 Cavity M 111 210 4.57 26 135 ! 255 5.54 26 I Wall.. Hollow M 3.91 26 Units M 95 180 S" Monovythe M 159 l 173 3.76 26 Hollow 2-Core j M 159
- 173 3.76 26 l
Joint Ec. G G"oc H 191 208 4.52 26 1 4-2-4 Cavity ofi M i 159 300 6.52 26 l ( Hollou Units Tied M i 159 300 6.52 26 6.52 2G i w/ Joint he. 6 8"oc :: i 159 i 300 i l I l I ( er 23 l
TAILE 9 (;: tir..:.;', 1 Moi,ulus 3 I-Mortar Ioadin of Pup:ure Construction Type Type l psf lNc: Arco, psi ACE */ Allo. F.et. l . 365 11.41 25 4" Hollou U Center 13E Monowy:he N 157 415 12.97 25 N 101 268 8.38 25 8" Hollou M 26S 20: 4.39 25 - Monowythe M 314 237 5.15 25 M 314 237 5.15 25 8" Bollow N 277 210 6.56 25 Monos.ythe N 314 u 237 7.41 25 t N-314 237 7.41 25 I~ 8" Bollou O 259 195 6.09 25 Monowythe O 277 210 6.56 25 l 0 277 210 6.56 25 i S" Uollow M 26B 202 4.39 25 Monowythe M 297 224 4.87 25 M 277 210-4.56 25 i 8" Hollow N. 277 210 6.56 25 N 259 195 6.09 25 Monowythe N 297 224 7.00 25 t' 4 271 8.45 25 S" Hollow 0 360 224 7.00 25 l l blonotythe 0 297 0 26S i 202 6.31 25 l ~ i. N 352 142 4.44 25 .L2" Hollow tionot.y tha N 314 127 3.97 25 N 333 134 4.19 25 9 O 24
- 5. t. 7
( Delert d) 5.1.8 ( Del e +ed) 5.1.9 ( Dele +c d ) 5.2 DAMPING The damping values for unreinforced walls are based on judgment This ar.d include a differentiation for the OBE and SSE force leve's. is based on the premise that damping increases as the stress level increases. The damping values for reinforced walls are based on the accepted values for reinforced concrete. There is no test data available in the literature to validate or 4efute these damping values. i 6.0 ANALYSIS AND DESIGN 6.1 STRUCTURAL RESPONSE OF UNREINFORCED WALLS j l 1 4 25
~ i G. I. I Cur c f Pt. a N 1 e rfsc 75 finik e le-n1c nf o / o +e pasl si.S, whi2*/, i.s y 5p ecif, cd in -t /ur.s c,cacn, <s e s cf ee cur a +e17 fredic+iy -lbc efec.+p24ic.sofcoeiyin arteched /c sco and variou.s bec,ndary,condwons. \\ f<*nylofyiny ess va>phens ere oc+ reyenred w>Wi dic. 2nol sir me-de cloloy y spe.c,peJ. y i 6.1.2 FREQUENCY VARIAT10NS OUT OF PLANE This section acknowledges the fact that there will be variations in the frequency of the wall as a result of uncertainties in the mass of the wall and attached equipment, material and section properties and the modulus of elasticity of the masonry. The method selected to account for these uncertainties was a variation in the modulus of elasticity. The range of i 25% for ungrouted walls and i 20% for grouted walls is conservative when coupled with the use of a smoothed spectrum. I O t -,-..c,
IN PLANE AND OUT OF PLANE EFFECTS 6.1.3 The plant FSAR provides for the design of a two-direction (one The provisions of this horizontal and one vertical) earthquake.The vertical component of section are consistent with the FSAR. motion is not included in the analysis procedure because the positive effect of the dead load on bed joint.etresses is not It should oe noted however included in the evaluation criteria. that the effect of vertical acceleration is included in determiring the pipe and equipment loads on the wall. 27 l
e t 6.2 ACCELERATIONS The masonry walls are analyzed in a manner similar to that of equipment and piping systems. It is therefore conservative to use the envelop of the floor level spectra to which the wall is attached. i If the wall is not attached at its top, forces will be induced from the floor level of the base of the wall and this should be used in the analysis. 6.4 IN PLANE EFFECTS Load bearing structural masonry w311s shall be evaluated on an The shear stress on the wall is determined allowable stress basis. from seismic analysis of the building and evaluated as in conventional design. The majority of the masonry walls are not intended to be primary structural elements and for the purposes of this specification a non. load bearing or non structural wall is defined as follows. It does not carry a significant part of the building's 1. story shear or moment. It does not ignificantly modify the behavior of adjacent 2. structural elements. 28
.~. In other words, the expected behavior of the building must ce substantially the same whether such walls are present or not. In-plane effects may be imposed on these masonry walls by the
- However, relative displacement between floors during seismic events.
the walls do not carry a significant part of the associated story shear, In addition, and their stiffness is extremely difficult to define. since the experimental evidence to date demonstrates that the apparent in-plane strength of masonry walls depends heavily Jpon.the in-plane stress boundary conaitions, load or stress en the walls is not a reasonable basis for an evaluation criteria. However, examination of the test data provided by the list of references for this section indicates that tha gross shear strain of walls is a reliable indicctor for predicting the onset of significant cracking. A significant crack is considered to be a crack in the central portion of the wall extending at least 10% of a wall's width Cracking along the interface between.a block wall and steel o-height. or concrete members does not limit the integrity of the wall, and is i not addressed here. The gross shear strain is defined to be: 8=' - where: % = strain ik = relative displacement between top and bottom of wall H = height of wall Test results indicate that to predict the initiation of significant cracking, masonry walls must be divided into two categories: Unconfined Walls - not bounded by adjacent steel or concrete 1. Significant " confining" stresses cannot primary structure. be expected. Co~nfined Walls - at a minimum, bounded top and bottom or 2. bounded on three sides. For unconfined concrete block masonry walls the works of Fiuiarn i and Becica (1) yield an allowable shear strain as defined above of 0. I It should be noted that Fishburn's test specimens were 15 days ola, on i average. 29 i
~ For confined walls, the most reliable data appears to be that of Mayes et al (4). In static and dynamic tests of masonry piers (con-fined top and bottom) 5 rying block properties, mortar properties, reinforcemant, vertical. id and grout conditions, significant It cracking was initiated at. rains exceeding about Y = 0.001. should be noted here that reinforcement can have no significant effect on the behavior prior to cracking. Similarly, the presence of cell grout should have no effect on stress or cracking in the mortar joints at a given strain. Both predictions are confirmed by the data in reference (4). In addition, the data shows that the onset of cracking is not sensitive to the magnitude of initial applied vertical load. Klingner and Berter0 (3) perfonned a series of cyclic tcsts tc frilure and found excellent correspondence with a non-linear analysis in which the behavior of an infilled frame prior to cracking is deter-While the equivalent strut mined by an equivalent diagonal strut. technique has been used by many investigators to study the stiffness and load-carrying mechanisms of infilled frames, Klingner and Bertere found that the quasi-compressive failure of the strut could be used to g predict the onset of significant cracking. After some simplification of the relations in reference (3), the strength of the strut corresponds to a strain at cracking II) ,3,(h) 1000B/H in which B = wall width H = wall height assuming E = 1000fln In sumary, the re:ommended value for pennissible in plane strain for service loads in unconfined walls is: ( = 0.0001 and in confined walls t ( = 0.001 For factored loads these strains may be increased by 1.67. Sc
. 7, ._2 .s., d For non-load bearing walls that are subjected to both in plane shear stresses and interstory drift effects the combination equation specified limits the combined effect such that the sum of the propor-The complexity of this tion of stress induced by each is less than 1. type of loading has not been validated by tests and the procedure recomended is deemed reasonable. e 6 1 l 5 N 4 31
t$~.:1'll'l/2/E4f//!.'lli Qr f, r I. 2 5 (e V 0 y t 2uin.w.......;i.....,r..t . m.....:/ w.,./..a m confined confined ~T'M!& h!* '?A*f/'E/9"/'L'% 1/N/ W'lin // P.*CPyg h 11 y s f. s
- t..
/i ? y K, y 1g 1 9 (ft ' m't s /~ i/i.L'. Ii /% a.5< e 4 sW f.ade6::,/,.';/a.-(i.67.6. tuli confined . confined l F.xa. ples TVfininc. Fi,oire " Confined" and, " Unconfined" Walls 1 t i a l Mihtilticpenkk.sh e.Os { unconfined e 32 r.. r
REFERENCES Becica, I.J. and H.G. Harris, " Evaluation of Techr.iques in the Direct Modeling 1. of Concre u Masonry Structures, " Drexel University Structural Models Laboratory Report ho. M77-1, June 1977. "Effect of Mortar Properties on Strength of Masonry," National Fishburn, C.C. 2. Bureau of Standards Monograph 36 U.S. Government Printing Office, Nov. 1961. Klingner, R.E. and V.V. Bertero, " Earthquake Resistance of Infilled Frames," 3. Journal of the Structural Division, ASCE, June 1978. Mayes, R.L., Cicugh, R.W., et al, " Cyclic Loading Tests of Masonry Piers," i 4. 76/8, 78/28, 79/i2 Earthquake Engineering Research Center, 3 volumes; EERC College of Engineering Universit, of California, Berkeley, California. Benjamin, J.R. and H.A. Williams, "The Behavior of One-Story Reinforced Concrete Shear Walls," Journal of the Structural Division, ASCE, Proceedings, Paper 1254 5. Vol. 83 No. ST3, May 1957, pp.1254.1-1254.39. Benjamin, J.R. and H.A. Williams, "The Behavior of One-Story Srick Shear Walls," 6. Journal of the Structural Division, ASCE, Proceedings, Paper 17(3, Vol. 84, ST4, July, 1958, pp. 1723.1-1723.30. ~ Benjamin, J.R. and H.A. Williams, " Behavior of One-Story Reinforced Co'ncrete 7. Shear Walls Containing Openings," Journal of the American Concrete Institute. Proceedings, Vol. 30, No. 5 November,1958, pp. 605.618. Holmes, M., " Steel Frames with Brickwork and Concrete Infilling," Proceedings 8. of the Institution of Civil Engineers, Vol.19, August,1961, pp. 473-08. Holmes, M., " Combined Loading on Infilled Frames," Proceedings of ?.he Inctitution 9. of Civil Engineers, Vol. 25, May,1963, pp. 31-38. Liauw, T.C., " Elastic Behavior of Infilled Frames," Proceedings of the Institution 10. of Civil Engineers, Vol. 46, July, 1970, pp. 343-349. Mallick, D.V. and R.T. Svern, "The Behavior of Infilled Frames Under Static 11. Loading," Proceedings of the Institution of Civil Engineers, Vol. 39, February, 1968, pp. 261-287. Smith, B.S., " Lateral Stiffness of Infilled Frames," Journal of the Structural 12. Division, ASCE, Vol. 38, No. ST6, December,1962, pp.183-199. Smith, B.S., " Behavior of Square Infilled Frames," Journal of the Structural 13. Division, ASCE, Vol. 91, No. ST1, February,1966, pp. 381-403. Smith, B.S., "Model Test Results of Vertical and Horiz 14. August,1968, pp. 618-623. f Smith, B.S. and C. Cartcc, "A Method of Analysis for Infilled Frames," Proceedi of the Institution of Civil Engineers, Vol. 44, September,1969, pp. 31-48. 15. 33
y..._..... ta e 6.6 EQUIPMENT The method specified to account for the effect of equipment is The effect of equipment mass is included in the fre-conservative. quency calculation of the wall and thu? the inertia effect of the mass of the equipment is included in the determination of the stress in the wall. This procedure by itself may not be sufficient because Thus it it does not account for any amplification of the equipment. is recommended that the fully amplified effect of the equipment be included by applying a static load and combining the resulting stresses with the stresses from the inertia loads. The combination shall be performed by the absolute sum method. Refinement to this procedure is permitted if the frequency of the equipment is known and the SRSS method of combining stresses can be justified. ~ 6.7 DISTRIBUTION OF CONCENTRATED OUT OF PL ANE i.0 ADS ~ g i The ellowable stresses for block pullout are based on the shear bond strength c. a block since this is the mode of failure for uncon-f The discussion given in Sec.5'.I.5 for the allowable fined block pullout. values for unreinforced shear walls indicates that these va. c5 accordance with the available test data on the shear bond strength of concrete masonry. 7.0 ( I)e f e t e d) ( f 4 34 -_}}