ML19340E209

Criteria for Re-evaluation of Concrete Masonry Walls.

ML19340E209
Person / Time
Site:	Three Mile Island
Issue date:	10/31/1980
From:	COMPUTECH ENGINEERING SERVICES, INC.
To:
Shared Package
ML19340E202	List: ML19340E201 ML19340E206 ML19340E209 ML19340E212 ML19340E213
References
IEB-80-11, NUDOCS 8101060641
Download: ML19340E209 (17)

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CRITERIA FOR THE RE-EVALUATION OF CONCRETE MASONRY WALLS THREE MILE ISLAND NUCLEAR STATION

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Prepared for .

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GPU SERVICE CORPORATION Parsipanny, NJ

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COMPUTECH ENGINEERING SERVICES, ING.

2150 Shattuck Ave.

Berkeley, CA

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October 1980

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CONTENTS Page 1.0 GENERAL

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......................... 1 1.2 Scope

.......................... 1 2.0 GOVERNING CODES . . . . . . . . ... . . . . . . . . . . . . . . 1 3.0 LOADS AND LO'AD COMBINATIONS . . . . . . . . . . . . . . . . . . 1 3.1 Service' Load Conditions ................. 1 3.2 Factored Load Conditions . . . . . . . . . . . . . . . . . 2 3.3 Definition of Terms ................... 2 4.0 MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4.1 Conc re t e Ma s on ry Un i t s . . . . . . . . . '. . . . . . . . . 2 4.2 Mo r ta r . . . . . . . . . . . . . . . . ......... 2 4.3 Grout .......................... 2 4.4 Horizontal Joint Reinforcing . . . . . . . . . . . . . . . 2 4.5 Bar Reinforcement .................... 3 5.0 DESIGN ALLOWABLES . . . . . . . . . . . . . . . . . . . . . . . 3 5.1

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Stresses . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.2 3ampin'g

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6. 0 ANALYSIS AND DESIGN . . . . . . . . . . . . . . . . . . . . . . 4 6.1 Structural Response of Unreinforced Masonry Walls .... 4

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6.2 Structural Response of Reinforced Masonry Walls .....

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6.3 Accelerations '

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6.4 Interstory Drift Effects . . . . . . . . . . . . . . . . . 8 6.5 In Plane Effects . . . . . . . . . . . . . . . . . . . . . 8 6.6 Equipme'nt ......................... 9 l

6.7 Distribution of Concentrated Out of Plane Loads

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7. 0 ALTERNATIVE ACCEPTANCE CRITERIA (OPERABILITY) . . . . . . . . . 10 l

7.1 Rei nfo rced Ma son ry . . . . . . . . . . . . . . . . . . . . 10 7.2 Unreinforced Masonry . . . . . . . . . . . . . . . . . . . 11 1

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CRITERIA FOR THE RE-EVALUATION OF CONCRETE MASONRY WALLS FOR THE THREE fille ISLAND NUCLEAR STATION UNIT 1 1.0 GENERAL -

1.1 Purpose This specification is provided to establish design requirements and criteria for use in ie-evaluating the structural adequacy of concrete block walls as required by NRC IE Bulletin 80-11, Masonry Wall Design, dated May 8, 1980. -

1.2 Scope The re-evaluation shall determine whether the concrete masonry walls will perform their intended function under loads and load-combinations specified herein. Concrete masonry walls not sup-porting safety systems but whose collapse could result in the loss of required function of safety related equipment or systems shall be evaluated to demonstrate that an SSE,- accident or '

tornado load will not cause failure to the extent that functions

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of safety related items is impaired. Verification of wall adequa'cy 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) will be used except as noted herein.

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3.0 LOADS AND LOAD COMBINATIONS ,

The walls shall be evaluated for the followipg loads.

3.1 Service Load Conditions D+R+T+E a

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3.2 Factored Load Conditions 1.250 + 1.0R + 1.25E 1.250 + 1.25T + 1.25E 1.0D + 1.0R + 1.0E' 1.00 + 1.0T + 1.0E' l.0D + 1.0T + 1.0W' 3.3 Definition of Terms D - Dead loads or their related internal moments and forces including any permanent equip.nent loads.

R - Pipe reactions during normai 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 pressurization).

4.0 MATERIALS '

The project specifications indicate that materials used for the performance of the work were originally.specified to meet the following requirements.

4.1 Concrete Masonry Units Hollow corcrete blocks: ASTM C-90 Grade N Solid concrete blocks: ASTM C-145 Grade N

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4.2 Mortar Mortar and mortar materials: AS'TM C-270 Type N

• 4.3 Grout None specified.

4.4 Horizontal Joint Reinforcing -

"Dur-o-wal" Standard Welded Steel - No. 9 rod ,

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4.5 Bar Reinforcement ASTM A-615-68 Grade 40 5.0 DESIGN ALLOWABLES

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5.1 Stresses Allowable stresses for the loads and load combinations given in Section 3.1 will be as given'in this section based on the following compressive strengths:

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• Hollow Concrete Units f' = 900 psi Solid Concrete Units f' = 950 psi Mortar Mg = 750 psi Stresses in the reinforcement and masonry shall be computed using working stress procedures. *

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The allowable stresses for service loads given in Section 3.1 shall be the S values given in Tables 1 and 2 for reinforced and unreinforced masonry respectively. For walls subjected to thermal effects the allowable ' stress shall be 1.3 times the S values given in Tables 1 and 2. The allowable stresses for the factored loads given in Section 3.2 shall be the U values given in Tables 1 and 2 for reinforced and unreinforced masonry respectively.

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5.2 Damping The damping values to be used shall be as follows:

Unreinforced Walis 2% - OBE 4% - SSE Reinforced Walls .

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4% - OBE 7% - SSE

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6.0 Af1ALYSIS Af1D DESIG?l 6.1 Structural Response of Unreinforced Masonry Walls 6.1.1 Out of Plane Effects The following sequence of analysis methods will be applied.

1. Walls without significant openings shall be assumed to be a simply supported beam spanning vertically and/or hori-zontally and the natural frequency shall be determined.

A fully grouted wall may be evaluated either as ar uncracked wall or if it is grouted it may be issumed thei. the mortar joint on the tension side is cracked and the moment of inertia calculated by neglecting the mortar and block on the tension side. If the latter is used the grout core

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tensile stress is evaluated.

2. The maximum moment and stress 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 frt-quency for the fundamental mode. If only one mode of vibration is calculated the moments and stresses shall be multiplied by 1.~05 to account for higher mode effects.

3. If the calculated stresses exceed the allowables or the wall has a significant opening (s) the wall shall be

. modeled as a plate with appropriate boundary conditions.

For a multimode analysis the modal responses shall be com-bined using the square root of the sum of the squares.

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4. If the calculated stresses eyceed the allowables and the wall is multiwythe steps 1, 2 and 3 shall be repeated using composite action if the wall contains a verifiable collar joint.

5. If the calculated stresses exceed the allowables in step 3 for a single wythe wall and step 4 for a multiwythe

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6.1.2 Frequency Variations in Out of Plane Uncertainties in structural *.equencies of the masonry wall resulting from variations in mass, modulus of elasticity, material and section properties shall be taken into account by varying the modulus of elasticity as follows:

UngroutedWalls-1000fyto600fy Grouted or l Solid Walls -1200fyto800fy If the wall frequency using the lower value of E is on the

. higher frequency side of the peak of the response spectrum it is considered conservative to use the lower value of E.

If the wall frequency is on the lower frequency side of the peak of the response spectrum the peak acceleration shall be used. If the frequency of the wall using the higher value of E is also on the lower frequency side of the peak the higher value of E may be used with its appropriate spectral value provided due consideration is given to frequency variations resulting from a.ll possible boundary condit:ons. -

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 satis tied the walls shall be considered to sati'fy the re-evalua-tion criteria. If either criterion is exceeded walls will be evaluated for operability.

6.1.4 - Stress Calculations

-tress calculations shall be performed by conventional n~ .. sos prescribec' by the Working Stress Design method.

The collar joint shear stress shall be determined by the relationship VQ/Ib.

6.2 Structural Response of Reinforced Masonry WP.lls 6.2.1 Out of Plane Effects The following sequence of analysis methods will be applied.

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1. Walls without significant openings will initially be assumed to be uncraclied and Steps 1 and 2 of Sec. 6.1.1 will be followed. Note that either or.both the uncracked section or the section neglecting the block and mortar on the tension side may be used. If the latter is used the grout core tensile stress.is evaluated. If the allowable stresses for an unreinforced wall given in Table 2 are

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exceeded the wall will be assumed to crack and the equivalent moment of inertia for a cracked section given in Sec. 6.2.2 shall be used. If the calculated stresses exceed the allowables of Table 1, Step 2 shall be used.

2. For walls with openings or those exceeding the reinforced stress levels in Step I the wall shall be modeled as a plate with appropriate boundary .

conditions assuming the wall is uncracked. See Step 1 for section properties. If the allowable stresses for an unreinforced wall given in Table 2 are exceeded the plate will be assumed to crack and

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the equivalent moment of inertia given in Sec. 6.2.2 shall be used. For a multimode analysis the modal

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res.ponses shall be combined using the square root of

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the sum of the squares. If the calculated stresses exceed the allowables of Table 2 a single w/the wall will be evaluated for operability; a multiwythe wall will be further evaluated using Step 3.

3. For multiwythe walls where a single wythe of the wall does not meet the stress criteria in Steps 1 and 2, Steps 1 and 2 shall be repeated using composite action provided the wall contains a verifiable collar joint.

6.2.2 Equivalent Moment of Inertia I

6.2.2.1 Uncracked Condition The equivalent moment of inertia of an nr. cracked wall (I t) shall be obtained from a transformed section con-sisting of the block, mortar, cell grout or core con-crete. (Note that a centrally reinforced wall has the same moment of inertia as an unreinforced section.)

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Alternatively if the mortar joint is assumed to crack or actually cracks the equivalent mcment of inertia may be calculated by neglecting the mortar and block on the tension side.

6.2.2.2 Cracked Condition i If the stresses due to all load combinations exceed

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the allowables the wall shall be considered to be cracked. In this event the equivalent moment of inertia (l )e shall either.be conservatively calculated from the fully cracked section properties of the wall

or as follows

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[Mcr33 fM 33

, cr j 1 =  ! 7 ) ,, y

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where:

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M cr = Uncracked moment capacity M = Applied maximum moment on the wall a

I = Moment of inertia of transformed section t

I cr = M ment of inertia of the cracked section f

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= 5 value of tensile stress defined in Table 2 multiplied by 2 for mortar and grout if the masonry joint is assumed to be cracked.

y = Distance of neutral plane from tension face If I e of Equation 1 is calculated this should be used over the full length of the wall. If I cr is 'Jsed this can be used in the cracked region only If the use of Ie results in an applied momemt Ma which is less than Mcr, then the wall shall be verified for NCT.

6.2.3 Frequency Variations l Uncertainties in structural frequencies of the masonry l wall resulting from variations in mass, modulus of elasticity, material and section properties shall be taken into account by varying the modulus of elasticity from 1200fm to 803fm-It is considered conservative to use the lower value of E if the wall frequency is on the higher frequency side of l 'the peak response spectrum. If the wall frequency using

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the lower values of E is on the lower fregi:ncy side of the peak of the response spectrum the peak acceleration shall be used. If the frequency of the wall using the higher value of E is also on the' lower frequency side of the peak the higher value of E may be used with its ap-

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propriate spectral value provided due consideration is given to frequency variations resulting from all possible l

boundary conditions.

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6.2.4 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 considered to satisfy the re-evaluation criteria. If either criterion is exceeded the walls will be evaluated for operability.

6.2.5 Stress Calculations 1

All stress calculations shall be performed by conventional methnds prescribed by the Working Stress Design method.

The collar joint shear stress shall N determined by thL

- relationship VQ/Ib for uncracked sections and in the com-pression zone of cracked sections. The relationship V/bjd shall be used for collar joints in cracked sections between the neutral axis and the tension steel.

6.3 Accelerations For a wall spanning between two floors the envelope of the spectra for the floor above and below shall be used to determine the stresses in the walls. -

6.4 Interstory Drift Effects The magnitude of interstory drift effects shall be determined from the original dynamic analysis.

6.3 In ilane Effects If a masonry wall is a N d bearing structural element shear

, stress'es shall be evaluated and compared with the allowable stresses of Tables 1 and 2.

If the wall is an infili panel or non-load bearing 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 s' trains for service loads. For factored loads the strains shall be multiplied by 1.67. The deflections shall be calculated by multiplying the permissible strain by the wall height.

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' Unconfined Wal.ls (I }

-y u = 0.0001 ,

Confined Walls (2) y c

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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.

(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.

If an infill panel or non-load bearing element.is subjected to both interstory drift effects and shear stresses due to inplane loads from equipment or piping the following criteria shall apply.

actual inplane shear stress actual interstory deflection

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allowable inplane shear stress allowable interstory deflection 40 A more refined analysis may be performed if necessary.

6.6 Equipment -

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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 l'0 lbs. the mass of the equipment shall be added to that of the wall in calculating the fregaency of the wall.

Stresses resulting from each piece of equipment weighing more

• than 100 lbs. shall be combined with the wall inertial loads using the absolute sum method. The SRSS method may be used

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provided its application is justified.

Stresses resulting from the equipnent ; hall be calculated by applying a static load consisting of the weight of equipment multiplied by the peak acceleration of the response spectrum

, for the floor level above the wall. If the frequency of the equipment is known it may be used to determine the static load.

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6.7 Distribution of Concentrated Out of Plane Loads 6.7.1 Bes.n or Jne Way Action

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For beam action local moments and stresses under a concentrated load shall be detemined using beam theory.

An effective width of four times the wall thickness shall be used; however, such moments shall not be taken as less than that for two way plate action.

6.7.2 Plate or Two Way Action For plate action local moments and stresses under a

' concentrated load shall be detemined using appropriate analytical procedures for plates or detemined numerically using a finite element analysis. -

A conservative ' estimate of the localized moment per unit length for plates supported on all edges can be taken as:

ML = 0.4P

• where: ML = Localized moment per unit length (in-lbs/in)

P = Concentrated load perpendicular to wall (lbs)

For loads close to an unsupported-edge the upper limit moment per unit length can be taken as:

ML = 1.2P 6.7.3 , localized Block Pullout For a concentrated load block pullout shall be checked using the allowable values for Unreinforced shear walls in Table 2. This allowable.shall be used for both rein-forced and unreinforced walls.

7.0 ALTE'mATIVE ACCEPTAf1CE CRITERIA'(OPEPABILITY) 7si Reinforced Masonry Where bending due to'out-of-plane inertial loading causes flexural stresses in the wall to exceed the allowable stresses for reinforced walls, the wall can be evaluated,by the " energy balance technique".

7.1.1 Effects on Equipment .

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If tr.a deflection calculated by the energy balance technique exceeds three times the yield deflection, the resulting de-flection shall be multiplied by a factor of 2 and a determi-nation made as to whether such factored displacements would

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adversely impact the function of safety-related systems attached and/or adjacent to the wall.

7.1.2 Effects on Walls The maximum deflection in the wall due to out-of-plane inertia loading shall be limited to 5 times the yield displacement. The yield displacement shall be calculated by reinforced concrete ultimate strength theory, and the masonry compression stresses of 0.85f' based on a rec-tangular stress distribution shall be used.

7.2 Unreinforced Masonry When, due to out-of-plane loading, the allowable stresses for unreinforced masonry are exceeded, the arching theory for masonry walls may be used to measure the ca acity of the walls. Due regard must be paid to the boundary conditions.

7.2.1 Limiting Deflection

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The deflection of the three hinged arch could be determined by assuming tilat the arch members are analogous to regular compression members in a truss. The method of virtual work (unit load method) may be used to compute the deflection at the arch interior hinge. The calculated deflection should not be more than 0.3T where the "T" is the thickness of the wall. A detennination should be made as to whether such calculated displacements would adversely impact the function of safety-related systems attached and/or adjacent to the wall.

7.2.2 Allowable Stresses The total resistance of the wall (f ) shall be calculated using the following stresses:

I. Tensile stress through the assumed tension crack shall be 6 @ for gro,uted walls or ft for ungrouted walls.

II. The crushing stress of block material = 0.85f'.

l By applying a factor of safety of 1.5 to the total resistance l (f ) as calculated above, the allowable load on the wall is limited to f /1.5.

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l 7.2.3 Boundary Supports The boundary supports should be clecked if they are capable of transmitting the reaction forces applied to them. The effect of support stiffness on the reaction forces should be considered.

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Table 1: Allowable Stresses in Reinforced Masonry

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I S U Allowable Maximum Allowable Maximum

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Description (psi) (psi) (psi) (psi)

Compressive Axial 0.22fy 100, 0.44f' 2000 Flexural 0.33fy 1200 0.85f' 2400

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Eearing 4

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On full area 0.25f' 900 0. 62 f' 1800 On one-third area 0.375f' 1200 0.95f' 2400 or less

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Shear Flexural members I2 1.1/fy 50 75 1.7ff' Shear Walls (3'4)

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Masonry Takes Shear M/Yd>l 0.9/f' 34' l.5 [y' 56 M/Vd = 0 74 2.0/f' 3.4}f' 123 Reinforceme.nt Takes Shear M/Vd>l' 75 2.5 125 1.5 /f' f' M/Vd- 0 Reinforcement 2.0 fy 120 3.4[ 180 i

Bond Plain Bars 60 80

' Deformed Bars 140 186 Tension

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Grade 40 20,000 0.9F y

Grade 60 24,000 0.9F y

Joint Wire r

.3F y 30,000 0.9F y

Compression 0.4F, 0.9F

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Notes to Table 1:

h (1) These values should be multiplied by (1 - (40t) I-(2) This stress should be evaluated using the effective area shown in

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s - a 6t or s$ acing I t, wh.chever es less for o o running bond

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a y aw [***w <

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4,e. .sm,med erreciive in tiew,.i como,ess.on. '

force normat to face

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FIGURE 1 (3) Net bedded area shall be used with these stresses.

(4) For M/Vd values between 0 and 1 interpolate between the values given for 0 and 1.

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Table 2: Allowable Stresses in Unr.einforced Masonry

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S U Allowable Maximum Allowable Maximum Description (psi) (psi) (psi) (psi)

Compressive .

Axial II) , 0.22f; 1000 0.44f; 2000 Flexural . 0.33f' 1200 0.85f; 3000 Bearing On full area 0.25f' 900 0.62f' 2250 On one-third area or less 0.375f' 1200 0. 95f ' 3000 Shear Flexural members (2, 3) < l.1 5'O 1.7ff' 75 Shear walls (2) 0.9/f' 34 1.35 [ 51 Tension Normal to bed joints Hollow units 0.5/m g 25 0.83{ 42 Solid or grouted 1.0/m g 40 1.67{ 67 Parallel to bed joints (4) I Hollow units 1.Q/mg 50 1.67/m g 84 Solid or grou+_d 80 134 1:5/mg 2.5/mg Grout Core 2.5/f' 4.2/f'c Collar joints ,

Shear 8 12

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Tension 8 12

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llotes to Table 2

(1) These values should be multiplied by (1 - (40t) )*

j (2) Use net bedded area with these stresses.

(3) For stacked bond construction use two-thirds of the values specified.

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(4) For stacked bond construction use two-thirds of the values specified for tension normal to the bed joints in the head joints of stacked bond construction.

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ENCLOSURE 3

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