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CRITERIA FOR THE RE-EVALUATION
OF CONCRETE MASONRY WALLS
THREE MILE ISLAND NUCLEAR STATION.
UNIT 1-
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Prepared for .
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GPU SERVICE CORPORATIONParsipanny, 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. . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Purposo ......................... 11.2 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 . . . . . . . . . . . . . . . . ......... 24.3 Grout .......................... 2
4.4 Horizontal Joint Reinforcing . . . . . . . . . . . . . . . 2
4.5 Bar Reinforcement .................... 3
5.0 DESIGN ALLOWABLES . . . . . . . . . . . . . . . . . . . . . . . 3
. 5.1 Stresses . . . . . . . . . . . . . . . . . . . . . . . . . 35.2 3ampin'g ......................... 4
6. 0 ANALYSIS AND DESIGN . . . . . . . . . . . . . . . . . . . . . . 4t
6.1 Structural Response of Unreinforced Masonry Walls 4....
6.2l Structural Response of Reinforced Masonry Walls 5,
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6.3 Accelerations '
i ...................... 8| 6.4 Interstory Drift Effects . . . . . . . . . . . . . . . . . 8:
6.5 In Plane Effects . . . . . . . . . . . . . . . . . . . . . 86.6 Equipme'nt ......................... 9
6.7 Distribution of Concentrated Out of Plane Loads 10l ~ .....
7. 0 ALTERNATIVE ACCEPTANCE CRITERIA (OPERABILITY) . . . . . . . . . 10l
7.1 Rei nfo rced Ma son ry . . . . . . . . . . . . . . . . . . . . 10
7.2 Unreinforced Masonry . . . . . . . . . . . . . . . . . . . 11
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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 requirementsand criteria for use in ie-evaluating the structural adequacyof 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 masonrywalls 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 theloss of required function of safety related equipment or systemsshall be evaluated to demonstrate that an SSE,- accident or
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tornado load will not cause failure to the extent that functions- of safety related items is impaired. Verification of wall
adequa'cy shall take into account support condition, globalresponse of wall, and local transfer of load. Evaluation ofanchor bolts and embedments are not considered .to be withinthe 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" (ACI531-79) 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+Ea
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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 forcesincluding 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 shutdownconditions, 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 (dueto pressurization).
4.0 MATERIALS '
The project specifications indicate that materials used for theperformance of the work were originally.specified to meet thefollowing requirements.
4.1 Concrete Masonry Units
Hollow corcrete blocks: ASTM C-90 Grade N
Solid concrete blocks: ASTM C-145 Grade N. .
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,
MMf2.
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4.5 Bar Reinforcement,
ASTM A-615-68 Grade 40
5.0 DESIGN ALLOWABLES.
5.1 Stresses
Allowable stresses for the loads and load combinations given inSection 3.1 will be as given'in this section based on the followingcompressive strengths:
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* Hollow Concrete Units f' = 900 psi
Solid Concrete Units f' = 950 psi
Mortar M = 750 psig
Stresses in the reinforcement and masonry shall be computed usingworking stress procedures. *
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The allowable stresses for service loads given in Section 3.1shall be the S values given in Tables 1 and 2 for reinforced andunreinforced masonry respectively. For walls subjected to thermaleffects the allowable ' stress shall be 1.3 times the S values givenin Tables 1 and 2. The allowable stresses for the factored loadsgiven in Section 3.2 shall be the U values given in Tables 1 and 2for 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% - OBE4% - SSE
Reinforced Walls.
- 4% - OBE7% - 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 bea 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 uncrackedwall or if it is grouted it may be issumed thei. the mortarjoint on the tension side is cracked and the moment ofinertia calculated by neglecting the mortar and block onthe tension side. If the latter is used the grout core
- tensile stress is evaluated.,
2. The maximum moment and stress shall be determined byapplying a uniform load to the beam. The maximum valueof the uniform load shall be mass times acceleration takenfrom the response spectrum curve at the appropriate frt-quency for the fundamental mode. If only one mode ofvibration is calculated the moments and stresses shall bemultiplied by 1.~05 to account for higher mode effects.
3. If the calculated stresses exceed the allowables or thewall has a significant opening (s) the wall shall bemodeled 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 thewall is multiwythe steps 1, 2 and 3 shall be repeatedusing composite action if the wall contains a verifiablecollar joint.
5. If the calculated stresses exceed the allowables in step3 for a single wythe wall and step 4 for a multiwythe
' wall the wall will be evaluated for operability. *
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6.1.2 Frequency Variations in Out of Plane
Uncertainties in structural *.equencies of the masonry wallresulting from variations in mass, modulus of elasticity,material and section properties shall be taken into accountby varying the modulus of elasticity as follows:
UngroutedWalls-1000fyto600fyGrouted or
| Solid Walls -1200fyto800fyIf the wall frequency using the lower value of E is on the
. higher frequency side of the peak of the response spectrumit is considered conservative to use the lower value of E.If the wall frequency is on the lower frequency side of thepeak of the response spectrum the peak acceleration shallbe used. If the frequency of the wall using the highervalue of E is also on the lower frequency side of the peakthe higher value of E may be used with its appropriatespectral value provided due consideration is given tofrequency variations resulting from a.ll possible boundarycondit:ons. -
6.1.3 In Plane and Out of Plane Effects
Provided both the allowable stress criteria for out of planeeffects and the in plane stress or strain criteria are satistied the walls shall be considered to sati'fy the re-evalua-tion criteria. If either criterion is exceeded walls willbe evaluated for operability.
6.1.4 - Stress Calculations
-tress calculations shall be performed by conventionaln~ .. sos prescribec' by the Working Stress Design method.The collar joint shear stress shall be determined by therelationship 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.'
1. Walls without significant openings will initially beassumed to be uncraclied and Steps 1 and 2 of Sec. 6.1.1will be followed. Note that either or.both the uncrackedsection or the section neglecting the block and mortar onthe tension side may be used. If the latter is used thegrout core tensile stress.is evaluated. If the allowablestresses for an unreinforced wall given in Table 2 are
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exceeded the wall will be assumed to crack and theequivalent moment of inertia for a cracked sectiongiven in Sec. 6.2.2 shall be used. If the calculatedstresses exceed the allowables of Table 1, Step 2shall be used.
2. For walls with openings or those exceeding thereinforced stress levels in Step I the wall shallbe modeled as a plate with appropriate boundary
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conditions assuming the wall is uncracked. SeeStep 1 for section properties. If the allowablestresses for an unreinforced wall given in Table 2are exceeded the plate will be assumed to crack and
. the equivalent moment of inertia given in Sec. 6.2.2-
' shall be used. For a multimode analysis the modal'
res.ponses shall be combined using the square root ofthe sum of the squares. If the calculated stresses'
exceed the allowables of Table 2 a single w/the wallwill be evaluated for operability; a multiwythe wallwill be further evaluated using Step 3.
3. For multiwythe walls where a single wythe of the walldoes not meet the stress criteria in Steps 1 and 2,Steps 1 and 2 shall be repeated using composite actionprovided the wall contains a verifiable collar joint.
6.2.2 Equivalent Moment of InertiaI
6.2.2.1 Uncracked Condition
The equivalent moment of inertia of an nr. cracked wall(I ) shall be obtained from a transformed section con-tsisting of the block, mortar, cell grout or core con-crete. (Note that a centrally reinforced wall hasthe same moment of inertia as an unreinforced section.)
' Alternatively if the mortar joint is assumed to crackor actually cracks the equivalent mcment of inertiamay be calculated by neglecting the mortar and blockon the tension side.
6.2.2.2 Cracked Condition
i If the stresses due to all load combinations exceedthe allowables the wall shall be considered to be.
cracked. In this event the equivalent moment ofinertia (l ) shall either.be conservatively calculatedefrom the fully cracked section properties of the wallor as follows: -
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[M 33 fM 3 3cr cr j y {1)! 7 , )1 = ,,
e (M j t gM cra a
I[ It )I- -
fM 2)=cr r iy /
where:
.M = Uncracked moment capacitycrM = Applied maximum moment on the wall
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I = Moment of inertia of transformed sectiont
I = M ment of inertia of the cracked sectioncrf = 5 value of tensile stress defined in Table 2I 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 of Equation 1 is calculated this should be usedeover the full length of the wall. If I is 'Jsed thiscrcan be used in the cracked region only
If the use of Ie results in an applied momemt Ma whichis less than Mcr, then the wall shall be verified forNCT.
6.2.3 Frequency Variations
| Uncertainties in structural frequencies of the masonry| wall resulting from variations in mass, modulus of elasticity,
material and section properties shall be taken into accountby varying the modulus of elasticity from 1200fm to 803fm-It is considered conservative to use the lower value of Eif the wall frequency is on the higher frequency side of
| 'the peak response spectrum. If the wall frequency usingthe lower values of E is on the lower fregi:ncy side of'
the peak of the response spectrum the peak accelerationshall be used. If the frequency of the wall using thehigher value of E is also on the' lower frequency side ofthe peak the higher value of E may be used with its ap-
- propriate spectral value provided due consideration isgiven to frequency variations resulting from all possibleboundary conditions.
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6.2.4 In Plane and Out of Plane Effects
Provided both the allowable stress criteria for out ofplane effects and the in plane stress or strain criteriaare satisfied the walls shall be considered to satisfy
the re-evaluation criteria. If either criterion isexceeded the walls will be evaluated for operability.
6.2.5 Stress Calculations1
All stress calculations shall be performed by conventionalmethnds 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/bjdshall be used for collar joints in cracked sections betweenthe neutral axis and the tension steel.
6.3 Accelerations
For a wall spanning between two floors the envelope of the spectrafor the floor above and below shall be used to determine the stressesin the walls. -
6.4 Interstory Drift Effects
The magnitude of interstory drift effects shall be determined fromthe original dynamic analysis.
6.3 In ilane Effects
If a masonry wall is a N d bearing structural element shearstress'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, shearstresses resulting from interstory drift effects will not becalculated. In this case the imposed interstory deflections ofSec. 6.4 shall be compared to the displacements calculated fromthe following permissible s' trains for service loads. Forfactored loads the strains shall be multiplied by 1.67. Thedeflections shall be calculated by multiplying the permissiblestrain by the wall height.
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' Unconfined Wal.ls (I }-y = 0.0001
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Confined Walls (2)y = 0.0008c
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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 toboth interstory drift effects and shear stresses due to inplaneloads from equipment or piping the following criteria shall apply.
actual inplane shear stress actual interstory deflectionallowable inplane shear stress allowable interstory deflection 40+
A more refined analysis may be performed if necessary.
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 l'0 lbs. themass of the equipment shall be added to that of the wall incalculating the fregaency of the wall.
Stresses resulting from each piece of equipment weighing morethan 100 lbs. shall be combined with the wall inertial loads*
using the absolute sum method. The SRSS method may be usedprovided its application is justified.,
Stresses resulting from the equipnent ; hall be calculated byapplying a static load consisting of the weight of equipmentmultiplied by the peak acceleration of the response spectrumfor 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
; 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 shallbe used; however, such moments shall not be taken as lessthan 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 appropriateanalytical procedures for plates or detemined numericallyusing a finite element analysis. -
A conservative ' estimate of the localized moment per unitlength for plates supported on all edges can be taken as:
M = 0.4P *
L
where: M = Localized moment per unit length (in-lbs/in)L
P = Concentrated load perpendicular to wall (lbs)
For loads close to an unsupported-edge the upper limitmoment per unit length can be taken as:
M = 1.2PL
6.7.3 , localized Block Pullout
For a concentrated load block pullout shall be checkedusing the allowable values for Unreinforced shear wallsin 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 flexuralstresses in the wall to exceed the allowable stresses for reinforcedwalls, the wall can be evaluated,by the " energy balance technique".
7.1.1 Effects on Equipment .,
If tr.a deflection calculated by the energy balance techniqueexceeds 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 systemsattached and/or adjacent to the wall.
7.1.2 Effects on Walls
The maximum deflection in the wall due to out-of-planeinertia loading shall be limited to 5 times the yielddisplacement. The yield displacement shall be calculatedby reinforced concrete ultimate strength theory, and themasonry 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 forunreinforced masonry are exceeded, the arching theory for masonrywalls may be used to measure the ca acity of the walls. Dueregard must be paid to the boundary conditions.
7.2.1 Limiting Deflection.
The deflection of the three hinged arch could be determinedby assuming tilat the arch members are analogous to regularcompression members in a truss. The method of virtual work(unit load method) may be used to compute the deflection atthe arch interior hinge. The calculated deflection shouldnot be more than 0.3T where the "T" is the thickness of thewall. A detennination should be made as to whether suchcalculated displacements would adversely impact the functionof safety-related systems attached and/or adjacent to thewall.
7.2.2 Allowable Stresses
The total resistance of the wall (f ) shall be calculatedusing the following stresses:
I. Tensile stress through the assumed tension crack shallbe 6 @ for gro,uted walls or f for ungrouted walls.
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II. The crushing stress of block material = 0.85f'.
| By applying a factor of safety of 1.5 to the total resistance| (f ) as calculated above, the allowable load on the wall is
limited to f /1.5.| 7.2.3 Boundary Supports
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The boundary supports should be clecked if they are capableof transmitting the reaction forces applied to them. Theeffect of support stiffness on the reaction forces shouldbe considered.
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- - Table 1: Allowable Stresses in Reinforced Masonry
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S U.
Allowable Maximum Allowable MaximumDescription (psi) (psi) (psi) (psi)
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Compressive
Axial 0.22fy 100, 0.44f' 2000
Flexural 0.33fy 1200 0.85f' 2400
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On full area 0.25f' 900 0. 62 f' 1800
On one-third area 0.375f' 1200 0.95f' 2400or less
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Shear
I2Flexural members 1.1/fy 1.7ff' 7550
Shear Walls (3'4),
Masonry Takes Shear
M/Yd>l 0.9/f' 34' l.5 [y' 56
M/Vd = 0 2.0/f' 743.4}f' 123
Reinforceme.nt TakesShear
M/Vd>l' 1.5 /f' 75 2.5 f' 125
M/Vd- 0 2.0 fy 120 3.4[ 180
Reinforcementi
Bond
Plain Bars 60 80
' Deformed Bars 140 186
Tension'
Grade 40 20,000 0.9FyGrade 60 24,000 0.9F
yJoint Wire .3F 30,000 0.9F
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y yCompression
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 inFigure 1.
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s - a
s$ acing6t orI t, wh.chever es less for
running bondo o
,A WQ'n XGp>i, ,
*,o., %.
[***wy awa <
t,.
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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 valuesgiven for 0 and 1.
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Table 2: Allowable Stresses in Unr.einforced Masonry.
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Allowable Maximum Allowable MaximumDescription (psi) (psi) (psi) (psi)
Compressive.
II)Axial 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' 1.35 [34 51
Tension
Normal to bed joints
0.83{Hollow units 0.5/m 25 42g
Solid or grouted 1.0/m 40 1.67{ 67g
Parallel to bed joints (4) I
Hollow units 1.Q/m 50 1.67/m 84g g
Solid or grou+_d 1:5/m 2.5/m 13480g g
2.5/f' 4.2/f'cGrout Core
Collar joints,
Shear 8 12,
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.;
(4) For stacked bond construction use two-thirds of the values specified'
for tension normal to the bed joints in the head joints of stackedbond construction.
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ENCLOSURE 3!
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