Text

Responds to IE Bulletin 80-11,Masonry Wall Design. Forwards Rept on Function & Configuration of Walls,Const Practices & re-evaluation Criteria.Wall Analysis Survey Will Be Submitted within 30 Days
	ML19345B326
Person / Time
Site:	Point Beach
Issue date:	11/14/1980
From:	Fay C; WISCONSIN ELECTRIC POWER CO.
To:	James Keppler; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
	IEB-80-11, NUDOCS 8011280081
	Download: ML19345B326 (41)
	v • d • e

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WISCONSIN Electnc eom couwa 231 W. MICHIGAN, P.O. BOX 2046. MILWAUKEE, WI 53201 November 14, 1980 G

Mr.

J.

G. Keppler, Regional Director hi 8

Office of Inspection and Enforcement, M

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Region III NE[l5 $

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S. NUCLEAR REGULATORY COMMISSION 799 Roosevelt Road

$EE U,

Glen Ellyn, Illinois 60137 2,'M) 2 E

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Dear Mr. Keppler:

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DOCKET NOS. 50-266 AND 50-301 180-DAY RESPONSE TO IE BULLETIN 80-11 MASONRY WALL DESIGN POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 This is to transmit our 180-day response to IE Bul'letin 80-11 dated May 8, 1980.

Enclosed herewith is a report entitled

" Report on the Re-evaluation of Concrete Masonry Walls for the Point Beach Nuclear Plant".

This report provides information requested by the bulletin, including the function and configuration of the walls, construction practices, re-evaluation criteria, and justification of the re-evaluation criteria.

The wall analysis using the referenced criteria is presently being completed and the wall analysis report will be submitted within thirty days from the date of this transmittal.

The wall analysis report will include a comparison of the walls to the appropriate evaluation criteria and a schedule for any upgrading work required.

If you have any questions regarding this submittal, please contact us.

Very truly yours, h/

dL/. /{ q'u C. W.

Fay, Director Nuclear Power Departme.nt Enclosure Copies to NRC Resident Inspector gy7 NRC Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C.

20555

'8011280

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Job No. 10447-016 REPORT ON THE RE-EVALUATION OF CONCRETE MASONRY WALLS FOR THE POINT BEACH NUCLEAR PLANT FOR WISCONSIN ELECTRIC POWER COMPANY By Bechtel Power Corporation San Francisco, California REV. O November 10, 1980 R-3/6

CONTENTS Page

1.0 INTRODUCTION

1 2.0 FUNCTION AND CONFIGURATIONS OF MASONRY WALLS 1

3.0 CONSTRUCTION PRACTICES 2

4.0 RE-EVALUATION CRITERIA AND COMMENTARY 4

APPENDICES:

A - FUNCTION AND CATEGORY OF SAFETY RELATED CONCRETE MASONRY WALLS B - CRITERIA FOR THE RE-EVALUATION OF CONCRETE MASONRY WALLS C - JUSTIFICATION FOR THE RE-EVALUATION CRITERIA L

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REPORT ON RE-EVALUATION OF MASONRY WALL DESIGN FOR THE POINT BEACH NUCLEAR PLANT

1.0 INTRODUCTION

The initial 60-day report required by the NRC I.E.

Bulletin 80-11 concerning masonry wall design was sent to the NRC under cover of Wisconsin Electric's letter to the NRC dated July 18, 1980.

A list of the masonry walls and blockouts, whose failure could affect safety related equipment which were identified by an inspection survey was included in the initial report.

A des-cription of the inspection survey conducted at Point Beach to identify safety related walls and the procedure used to perform the inspection survey were also included in the initial report.

This report is the 180 day report required by the bulletin.

Bechtel Power Corporation has assembled the report based on cri-teria, justification and preliminary analyses prepared by Computech Engineering Services, Inc.

2.0 FUNCTION AND CONFIGURATIONS OF MASONRY WALLS The function of the masonry walls at the Point Beach Nuclear Plant is one or more of the following: fire protection /separa-(

tion, radiation shielding, room partition or security barrier.

The masonry walls were not intended to function as bearing walls.

They are not part of the lateral force resisting sys-tems of the buildings in which they are located.

The safety related walls are grouped into four categories based on func-tion and configuration as follows:

a.

Masonry walls

b. Masonry blockouts in concrete walls

c. Unreinforced concrete blockouts in concrete walls

d. Masonry facings provided for fireproofing around steel building columns The masonry and unreinforced concrete blockouts mentioned above were openings left in the plant concrete walls for routing of piping, conduit, and cable trays, and for moving large equipment into interior rooms.

A list of all the safety related walls is provided in Appen-dix A.

The function and category of each wall on the list are described.

Each safety related wall is identified by a unique number.

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The type and strength of the materials of which the walls were constructed are described in Section 4.0 of Appendix B " Criteria for the Re-evaluation of Masonry Walls".

The wall strength evaluation is based on chipping investiga-tions in addition to construction drawings.

3.0 CONSTRUCTION PRACTICES 3.1 General Bechtel Corporation was the prime construction con-tractor for the Point Beach Nuclear Plant.

The masonry construction work was awarded to a subcontractor.

The subcontractor executed the work in accordance with a specification written by Bechtel Corporation for the supply and construction of masonry.

Quality was ensured by the general practices employed by Bechtel in the selection of subcontractors, and the use of affiliated unions and related masonry workmen.

It is the general practice to hold a preconstruction meeting at which approach and methods of construction are discussed.

Coordination and administration of the actual work on the site was done by Bechtel engineers

{ _

who also performed the inspection of completed construc-tion.

The following requirements were included in the specific-tion for Point Beach covering the construction of masonry:

3.2 Workmanship Each course of concrete blocks was required to be j

solidly bedded in mortar and blocks were to have full mortar coverage on horizontal faces, and at least to the depth of the face shell on the ver-tical faces.

Anchors, wall plugs, accessories and other items were to be solidly embedded in grout filled block cells.

Block cells to be filled with grout were required to be kept free from mortar droppings.

Clean out holes were to be carefully closed before filling.

Bricks were required to be laid in full beds accord-ing to concrete block coursing with solid joints.

Backs of bricks against back-up block were to have full mortar joints.

It was required that brick should be wetted 3 to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> before need but that

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it should be free from water adhering to their sur-faces when placed in the wall.

During freezing weather, units were required to be sprinkled with warm water just before laying.

Mortar was required to be prepared in batches of a size that would be used before the initial set occurred and placed within two hours after mix-ing.

Mortar which was stiffened was required to be retempered to restore its workability and water added as needed only within the maximum time interval specified above.

Grout was required to be mixed in a clean mech-anical mixer with only sufficient water added to produce a plastic mix which would flow readily into place without segregation.

It was stipu-lated that grout should not be used more than 45 minutes after adding the water.

It was required that grout should be poured in lifts not to exceed four feet and that each pour should be thoroughly rodded to insure compaction and bond to the preceding pour.

It was also stipulated that when work was to be stopped for 1(

a period of 45 minutes or longer, the pour at the

'A top of the last course and the surface of the grout should be thoroughly roughened.

When work was resumed, the laitance was to be removed and the existing grout dampened and coated with neat cement before additional grout was poured.

Before delivery of any masonry units to the site the subcontractor was required to submit for approval at the site at least three samples of each unit proposed to be used in the masonry con-struction.

No work was to be started until such approval was receivad by the subcontractor.

Before constructing any brick faced walls or glazed block walls the subcontractor was required to build a sample wall of approximately twenty square feet for approval by the contractor.

Such sample walls were required to be maintained as a standard for the course of the work.

3.3 Tests and Certificates Testing of items for strength was the responsi-bility of Bechtel Corporation.

Samples for strength i

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tests.were provided by the subcontractor.

Test-i ing of bricks and mortar for efflorescence was the responsibility of the subcontractor.

The sub-contractor was required to obtain a certificate from a reputable laboratory stating that the brick selected had been tested for efflorescence in ac-cordance with ASTM C 67 and that it had passed the test with a rating of not more than "slightly

" effloresced".

Mortar for brick was required to be tested by a reputable laboratory to verify that the mortar i

would not cause unacceptable efflorescence on i

the brick.

The procedure for testing was des-

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cribed in detail in the specification.

The subcontractor was required to furnish a i

certificate verifying that all concrete blocks had been properly and thoroughly cured at the plant before shipping.

4.0 RE-EVALUATION CRITERIA AND COMMENTARY 4.1 Criteria

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Appendix B contains the criteria used for the re-evaluation of the safety-related masonry I

walls for the Point Beach plant.

Loads and load combinations for which the re-evalua-tion has been performed are included in the criteria.

The walls have been analyzed for both safety related and non-safety related attachments.

The differential floor displace-men.',s and thermal effects are not considered to be self limiting.

The loads induced by the floor displacements are considered as des-cribed in Sections 6.4 and 6.5 of Appendix B.

The load combinations listed in Sections 3.1 and 3.2 of Appendix B include thermal effects.

The re-evaluation criteria have been developed 4

to ensure that no significant cracking will occur in the masonry walls under dynamic loads.

Appendix B addresses accep' nce criteria for 3

both in-plane and out-of-plane loads.

The Point Beach FFDSAR provides for the design of a two-direction (one horizontal and one i

vertical) earthquake.

As stated in Section I

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6.1.3 and 6.2.4 of Appendix B, each wall is evaluated independently for these two load combinations.

The individual wythes of a multi-wythe wall are evaluated as single wythe walls.

If they do not qualify as single wythe walls, the wall is evaluated as a multiwythe wall provided it has a verifiable collar joint and acceptable collar joint stresses are estab-lished.

The distribution of local loadings j

such as piping and equipment support reactions and block pullout is addressed in Section 6.7 l

of Appendix B.

4.2 Criteria Justification Appendix C is the justification for the criteria contained in Appendix B and provides justifica-tion of tne criteria by reference to existing codes, test data and standards of practice.

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APPENDIX A FUNCTION AND CATEGORY OF SAFETY RELATED CONCRETE MASONRY WALLS FOR POINT BEACH NUCLEAR PLANT

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FUNCTION AND CATEGORY OF SAFETY RELATED CONCRETE MASONRY WALLS Wall No.

Function Category 3

Shielding Masonry Wall 39 Shielding Masonry Wall 40 Shielding Masonry Wall 5-5 Shielding / Fire Protection Masonry Wall 5-29 Shielding / Fire Protection Masonry Wall

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5-7 Shielding Masonry Wall 24 Shielding Masonry Wall 26 Shielding Ma,sonry Wall 157 Shielding Masonry Wall 19 Fire Protection Masonry Wall 20 Fire Protection Masonry Wall 22-A Security _ Barrier Masonry Wall 86 Shielding Masonry Wall

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151 Shielding Masonry Wall 152 Shielding Masonry Wall 72 Shielding Masonry Wall 64 Shielding Masonry Wall 65 Shielding Masonry Wall

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68 Partition Masonry Wall R3/1

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Wall No.

Function Category 104 Shielding Masonry Wall 143 Shielding Masonry Wall 133 Partition Masonry Wall 111-1 Partition / Fire Protection Masonry Wall 111-2 Partition / Fire Protection Masonry Wall 111-3 Partition / Fire Protection Masonry Wall 111-4 Partition / Fire Protection Masonry Wall 112 Partition / Fire Protection Masonry Wall

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113 Partition / Fire Protection Masonry Wall 114 Partition / Fire Protection Masonry Wall 115 Partition / Fire Protection Masonry Wall 116 Partition / Fire Protection Masonry Wall 60 Fire Protection Masonry Wall 98 Fire Protection Masonry Wall 99 Fire Protection Masonry Wall 8-2, Fire Protection Concrete Filled Blockout 8-9 Fire Protection Concrete Filled

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Blockout 1

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Wall No.

Function Category 5-31 Shielding / Fire Masonry Filled Protection Blockout 4

30 Fire Protection Masonry Filled Blockout 5-12 Fire Protection Masonry Filled i

Blockout 5-22 Shielding Masonry Filled Blockout 4

5-24 Shielding Masonry Filled Blockout 14 Shielding Masonry Filled Blockout 45 Shielding / Fire Masonry Filled Protection Blockout 22 Fire Protection Masonry Filled Blockout 23 Fire Protection Masonry Filled Blockout 3-1 Fire Protection Masonry Filled Blockout j

3-6 Partition Masonry Filled Blockout 3-7 Partition Masonry Filled Blockout i

3-10 Fire Protection Concrete Filled Blockout 3-11 Fire Protection, Concrete Filled -

Blockout 8-45 Shielding Concrete Pilled Blockout i

5-51 Fire Protection Masonry Filled Blockout

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Wall No.

Function Catecory j

71 Fire Protection Masonry Filled j

Blockout i

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109 Shielding Masonry Filled l

Blcckout i

134-C Shielding Masonry Filled Blockout 1

161-1 Fire Protection Masonry Pacing on Steel Column i

161-2 Fire Protection Masonry Facing on i

Steel Column i

i 161-3 Fire Protection Masonry Facing on Eteel Column

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162-1 Fire Protection Masonry Facing on Steel Column 162-2 Fire Protection Masonry Pacing on Steel Column 1

162-3 Fire Protection Masonry Facing on I

- Steel Column 146 Fire Protection Masonry Facinq on Steel Column 147 Fire. Protection Masonry Facinq on Steel Column 4

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i APPENDIX B CRITERIA FOR THE RE-EVALUATION OF CONCRETE MASONRY WALLS For Point Beach Nuclear Plant t

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C CONTENTS Page 1.0 GENERAL 1

1.1 Purpose I

1.2 Scope...........................................

1 2.0 GOVFPNING CODES 1

3.0 LOADS AND LOAD 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 Concrete Masonry Units 2

4.2 Mortar 3

4.3 Grout 3

4.4 Horizontal Joint Reinforcing 3

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4.5 Bar Reinforcement 3

4.6 Facing Brick 3

5.0 DES 1GN ALLOwABLES 3

5.1 Stresses 3

5.2 Damping..................................;......

4 6.0 ANALYSIS AND DESIGN 4

6.1 Structural Response of Unreinforced Masonry Walls 4

6.2 Structural Response of Reinforced Masonry Walls..

6 6.3 Accelerations 10 6.4 Interstory Drif t Effects 10 6.5 In Plane Effects 10 6.6 Equipment 11 6.7 Distribution of Concentrated Out of Plane Loads..

11-7.0 ALTERNATIVE ACCEPTANCE CRITERIA (OPERABILITY) 12 7.1 Re i n f o r c ed Ma so n ry.............................

12 7.2 Unreinforced Masonry............................

13 8.0 CRITERI A FOR EVALUATION OF MASONRY BLOCKOUTS..........

13 8.1 Blockouts Spanning Vertica11y....................

13 8.2 Blockouts Spanning Horizontally..................

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C-CRITERIA FOR THE RE-EVALUATION OF CONCRETE MASONRY WALLS FOR THE POINT BEACH NUCLEAR PLANT 1.0 GENERAL 1.1 Purpose These criteria are provided to establish design re-quirements and criteria for use in re-evaluating the structural adequacy of masonry 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 masonry walls will perform their intended function under loads and load combinations specified herein.

Masonry walls

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not supporting safety systems but whose collapse could result in the loss 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 related 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 AND LOAD COMBINATIONS The walls shall be evaluated for the following loads.

3.1 Service Load Conditions D+R+T+E

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3.2 Factored Load Conditions 1.25 D + 1.0R + 1.25E 1.25D + 1.25T + 1.25E 1.0D + 1.0R + 1.0E' l.0D + 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 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).

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 Concrete Blocks:

ASTM C-90 Grade U-l with linear shrinkage limited to 0.05 percent.

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4.2 Mortar i

j Mortar and mortar materials: ASTM C-270 Type N.

j 4.3 Grout i

l Materials proportioned to produce a grout having a minimum compressive strength of 2500 psi at 28 days.

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i 4.4 Horizontal Joint Reinforcing

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5 "Du-ro-wal" standard truss type (or equal).

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4.5 Bar Reinforcement i

ASTM Designation A15, intermediate grade, deformed j

bars per ASTM 305.

j 4.6 Facing Brick ASTM designation C216-65, Grade SW, Type FBX.

5.0 DESIGN ALLOWABLES l{

5.1 Stresses Allowable stresses for the loads and load com-binations given in Section 3.1 will be as given in this section based on the following compres-sive strengths:

Hollow Concrete Units f'm = 1000 psi Hollow Concrete Units f', = 1000 psi Grouted Solid Solid concrete Units f',=

1000 psi i

Stresses in the reinforcement and masonry shall i

l be computed using working stress procedures.

l 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 l

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For walls subjected to thermal 1

effects the allowable stress shall be 1.3 times the S values given in Tables 1 and 2.

The allow-able stresses for the factored loads given in j

l Section 3.2 shall be the U values given in Tables 1 and 2 for reinforced and unreinforced masonry respectively.

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

i Unreinforced walls 2% - OBE 4%

SSE Reinforced walls 1

2 41 - OBE 7% - SSE 6.0 ANALYSIS AND DESIGN 6.1 Structural Response of Unreinforced Masonry Walls

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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 spanninq vertically and/or horizontally and the natural frequency shall be determined.

A fully grout-ed wall may be evaluated either as an uncracked wall, or if it is grouted, it may be assumed that the mortar joint on the tension side is cracked and the moment of inertia calculated by neglect-ing the mortar and block on the tension side.

If the latter is used the grout core tensile stress is evaluated.

2.

The maximum moment and stress shall be deter-4 mined by applying a uniform load to the beam.

The maximum value of the uniform load shall be mass times acceleration taken from the re-sponse spectrum curve at the appropriate fre-quency for the fundamental mode.

If only one mode of vibration is calculated, the moments and

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stresses shall be multiplied by 1.05 to account 1

for higher mode effects.

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3.

If the calculated stresses exceed the allow-ables or the wall has a significant opening (s),

the wall shall be modeled as a plate with ap-propriate boundary conditions.

For a multi-mode analysis the modal responses shall be combined using the square root of the sum of the squares.

I 4.

If the calculated stresses exceed the allow-i ables and the wall is multiwythe, steps 1, 2 and 3 shall be repeated using composite action if the wall contains a verifiabic collar joint.

5.

If the calculated stresses exceed the allow-ables in step 3 for a single wythe wall and step 4 for a multiwythe wall, the wall will be evaluated for operability.

6.1.2 Frequency Variations in Out of Plane Uncertainties in structural frequencies of the 4

i masonry wall resulting from variations in mass, modulus of elasticity, material and section prop-r 3

erties shall be taken into account by varying the 7

modulus of elasticity as follows:

Ungrouted walls - 1000f', to 600f',

Grouted or Solid Walls

- 1200f', to 800f',

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 conser-vative 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 accelera-tion 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 all possible boundary conditions.

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6.1.3 In Plane and Out of Plane Ef fects 4

4 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, walls will be evaluated for operability.

6.1.4 Stress Calculations All stress calculations shall be performed by l

conventional methods prescribed by the Working Stress Design method.

The collar icint shear j

stress shall be determined by the relationship 4

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j 6.2 Structural Response of Reinforced Masonry Walls i

6.2.1 Out of Plane Effects J

J The following sequence of analysis methods will be applied.

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1.

Walls uithout significant openings will l (

initially be assumed to be uncracked and Steps 1 and 2 of Sec. 6.1.1 will be followed.

Note that either or both the uncracked sec-tion 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 4

for an unreinforced wall given in Table 2 are 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 1 the wall i

shall be modeled as a plate with appropriate boundary conditions sssuming the wall is un-cracked.

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 the equivalent

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I moment of inertia given in Sec. 6.2.2 shall be used.

For a multimode analysis, the modal responses shall be combined using the square root of the sum of the squares.

If the cal-t culated stresses exceed the allowables of i

Table 2, a single wythe wall will be evaluated for operability; a multiwythe wall will be further evaluated using Step 3.

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3.

For multiwythe walls where a single wythe of the wall does not meet the stress cri-teria in Steps 1 and 2, Steps 1 and 2 shall a

be repeated using composite action provided

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the wall contains a verifiable collar joint.

6.2.2 Equivalent Moment of Inertia 6.2.2.1 Uncracked Condition i

The equivalent moment of inertia of an un-cracked wall (Ie) shall be obtained from a i

transformed section consisting of the block, I

mortar, cell grout or core concrete.

(Note that a centrally reinforced wall has the same moment of inertia as an unreinforced I

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section.)

Alternatively if the mortar joint is assumed to crack or actually cracks the equivalent moment of inertia may be calcu-1 lated by neglecting the mortar and block on the tension side.

G.2.2.2 Cracked Condition If the stresses due to all load combinations exceed the allowables the wall shall be con-sidered to be cracked.

In this event the equivalent moment of inertia (Ie) shall either be conservatively calculated from.the fully cracked section properties of the wall or as follows:

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= S value of tensile stress defined in r

Table 2 multiplied by 2 for mortar and grout if the masonry joint is assumed to be cracked.

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shou $d be used over the full length of the wall.

If I is used, this can be used in the cra$ked region only.

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If the use of I results in an applied e

moment M which is less than M t

the wall shall be verified for E,r* hen a

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6.2.3 Frequency Variations Uncertainties in structural frequencies of the masonry wall resulting from variations in mass, 1

modulus of elasticity, material and section properties shall be taken into account by vary-

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ing the modulus of elasticity from 1200f', to l

800f'n.

It is considered conservative to use the lower value of E if the wall frequency is i

on the higher frequency side of the peak re-sponse spectrum.

If the wall frequency using the lower values of E is on the lower frequency side of the peak of the response spectrum the

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peak acceleration shall be used.

If the fre-quency 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-propriate spectral value provided due considera-tion is given to frequency variations resulting from all possible boundary conditions.

6.2.4 In Plane and Out of Plane Effects Provided both the allowable stress criteria for

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out of plane effects and the in plane stress or strain criteria are satisfied, the walls shall be considered to satisfy the re-evaluation cri-teria.

If either criterion is exceeded, the i

walls will be evaluated for operability.

6.2.5 Stress Calculations All stress calculations shall be performed by conventional methods prescribed Ly the Workino Stress Design method.

The collar ioint shear stress shall be determined by the relationship V0/Ib for uncracked sections and in the com-pression zone of cracked sections.

The rela-tionship V/bjd shall be used for collar joints in cracked sections between the neutral axis and the tension steel.

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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.

6.5 In Plane Effects t

If a masonry wall is a load bearing structural ele-i ment shear stresses shall be evaluated and compared with the allowable stresses of Tables 1 and 2.

If the wall is an infill 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 strains for service Joads.

For factored loads, the strains shall be multiplied by

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1.67.

The deflections shall be calculated by multi-plying the permissible strain by the wall height.

Unconfined Walls III Yu = 0.0001 Confined Walls (2)

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.

(b) On the top and bottom of the i

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 sub-jected to both interstory drift effects and shear stresses due to inplane loads from equipment or piping, 4

the following criteria shall apply.

' R3/6.

-T--

---ers v

--++4*

t-ee e'

-r-w

-m+----

~--w------t--

r-

-w

-r--

+ ~-

- :+--- -*- ---- - - - + --"

--W-'ew

~

l

C.

actual inplane actual inter-shear stress story deflection 1

allowable inplane allowable inter-shear stress story deflection A more refined analysis may be performed if necessary.

l 6.6 Equipment l

If the total weight of attached equipment is less than 100 lbs., the effect of the equipment on the wall shall 1

i i

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 fr:

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 i{

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 equipnent is unknown.

If the frequency i

of the equipment is known, it may be used to determine the 1

static load.

6.7 Distribution of Concentrated Out of Plane Loads 6.7.1 Beam or One Way Action For beam action, local moments and stresses under a concentrated load shall be determined 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 those for two way plate action.

6.7.2 Plate or Two Way Action j

For plate action, local moments and stresses under a concentrated load shall be determined using appropriate analytical procedures for plates or determined numerically using a finite element analysis.

k-A conservative estimate of the localized moment per unit length for plates supported on all edges

{

can be taken as:

R3/6 j

i C

Mg = 0.4P t

where: M n

g 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:

Mg = 1.2P 6.7.3 Localized Block Pullout For a concentrated load, block pullout shall be checked using the allowable values for unrein-forced shear walls in Table 2.

This allowable shall be used for both reinforced and unrein-forced walls.

7.0 ALTERNATIVE ACCEPTANCE CRITERIA (OPERABILITY) f 7.1 Reinforced Masonry k

Where bending due to out-vf-plane inertial loading 4

causes flexural stresses in the wall to exceed the 4

allowable stresses for reinforced walls, the wall can be evaluated by the " energy balance technique".

7.1.1 Effects on Equipment If the deflection calculated by the energy bal-ance technique exceeds three times the yield de-flection, the resulting deflection shall be multiplied by a factor of 2 and a determination made as to whether such factored displacements would 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 dis-placement shall be calculated by reinforced concrete ultimate strength theory, and the masonry compression stresses of 0.85f'$all be based on a rectangular stress distribution s k

used.

R3-6 1 e

-t

,-.-..-.-.--m,

7.2 Unreinforced Masonry When, due to out-of-plane loading, the allowable stresses for unreinforced masonry are exceeded, the archinq theory for masonry walls may be used to measure the capacity of the walls.

Due regard must be paid to the boundary conditions.

7.2.1 Limiting Deflection The deflection of the three hinned arch could be determined by assuming that 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 deflec-tion should not be more than 0.3T where the "T"

is the thickness of the wall.

A determination should be made as to whether such calculated displacements would adversely impact the func-tion 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 throuqh the assumed tension crack shall be 6 f'

f f r ungrouted wal$s.or grouted walls or f t II. The crushing stress of block material =

0.85f'm' 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 The boundary sunports should be checked if they are capable of transmitting the reaction forces applied to them.

The effect of support stiffness on the reaction forces should be considered.

8.0 Criteria for Evaluation of Masonry Blockouts 8.1 Blockouts spanning vertically.

For evaluation of blockouts spanning vertically, criteria described k_

in Section 7.2 will be used.

R3/6

(

8.2 Blockouts spanning horizontally.

For the evaluation of blockouts spanning horizontally, the provisions of Section 6.0 will be used.

t R3/6 t

[

Table 1:

Allowable Stresses in Reinforced Masonry S

U Allowable Maximum Allowable Maximum Des,cription (psi)

(psi)

Compressive 0.22f',

1000 0.44f',

2000 Axial (l)

Flexural 0.33f',

1200 0.85f',

2400 Bearing On full area 0.25f',

900 0.62f',

1800 i

On one-third 0.375f',

1200 0.95f',

2400 area or less Shear Flexural members (2) y,1 gi 50 1.7/',

75 m

(

Shear Walls (3,4)

Masonry Takes 1

Shear M/Vd)1 0.9 34 1.5 f'm 56 M/Vd = 0 2.0 74 3.4 123 Reinforcement Takes' Shear M/Vdyl 1.5[f',

75 2.5 125 M/Vd = 0 2.0 f',

120 3.4 180 Reinforcement Bond Plain Bars 60 80 Deformed Bars 140 186 Tension

-yl Grade 40 20,000 0.9F Grade 60 24,000 0.9F y Joint Wire

.5F or 0.9F Yl l(

(

30 000 Compression 0.4F 0.9F y

y R3-6 4

=

l

l..

(

Notes to Table 1:

1 (1)

These values should be mtiltiplied by 40t)3),

l h

gy_g (2)

This stress should be evaluated using the effective area showa in Figure 1.

i

=

- 6i CR RE8AR 6 PAC /NG

=

hW/CHEVER /S LE&9 /DR RUNN/NG LOVD t

t, 1

i ir IP

)

f/////////////// V////////////// //////s 7.r 6

l/

,r,..,

/

,,,4.

i n;p.,.;,.:.

y r

I

, w

~

7 i

r a

i AREA ASSUMED EFFECT/VE /N Fl.EXUA?AL COMPR'ESS/ON, FORCE NORMAL 70 FACE 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.

4 l

i R3-6 '

v.

r-__,

y_ _.

4

(

Table 2:

Allowable Stresses in Unreinforced Masonry S

U Allowable Maximum Allowable Maximun Description (psi)

(psi)

(psi) j Compressive Axial (I) 0.22f',

1000 0.44f'm 2000 Flexural 0.33f',

1200 0.85f'm 3000 Bearing l

On full area 0.25f',

900 0.62f',

2250 On one-third area or less 0.375f',

1200 0.95f',

3000 i

i Shear Flexural (2,3) l

1. 7 [

members 1,i f.

50 75 m

{

Shear walls (2) 0.9ff'm 1.35/f'm 34 51 Tension Normal to bed joints 0.5 [

l Hollow units 25 0.83 g 42 l

=

Solid or grouted 1.0gm 40 1.67 g 67 o

l Paralle{

o bed i

Joints Hollow units 1.0/m 50 1.67pm 84 o

o Solid or grouted 1.5 K 80 2.5 g 134

[

Grout Core 2.5/f'c 4.2 Collar joints Shear 8

12 Tension 8

12

(

R3-6,

,-m..,

..----r,-

.-v,----,----

,w--

l \\

Notes to Table 2:

(1)

These values should be multiplied by h

T3t)3)*

( y_g (2)

Use net bedded area with these str

.ses.

(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 stacked bond construction.

R3-6 O

(

APPENDIX C JUSTIFICATION FOR THE CRITERIA FOR THE RE-EVIIU1. TION OF CONCRETE MASONRY WALLS FOR POINT BEACH NUCLEAR PLANT (r

's r

4 R-3/3

= - -. -

p CONTENTS i [

Page j

1.0 GENERAL.........................

1 1

_2.0 GOVERNING CODES...................~.

1

~

I 3.0 LOADS AND LOAD COMBINATIONS..............

2 4.0 MATERIALS.......................

2 S.O DESIGN ALLOWABLES...................

2 5.1 ALLOWABLE STRESSES................

2 1

5.2 DAMPING 28

'l 6.0 ANALYSIS AND DESIGN..................

28 i

6.1 STRUCTURAL RESPONSE OF UNREINFORCED WALLS 28 6.2 STRUCTURAL RESPONSE OF REINFORCED MASONRY WALLS 30

t 6.3 ACCELERATIONS 31

(-

6.5 IN PLANE EFFECTS.................

31 6.6 EQUIPMENT 37

{

6.7 DISTRIBUTION OF CONCENTRATED OUT OF PLANE LOADS 37 t

I 7.0 ALTERNATIVE ACCEPTANCE CRITERIA............

37 7.1 REINFORCED MASONRY................

37 7.2 UNREINFORCED MASONRY...............

38 i

w,w

--y

.rw--v.

v--

y

--m r-

---,-m-

~- --. - -

r- - --- <

..m 4m---+r--e. -

(

JUSTIFICATION FOR THE i

CRITERIA FOR THE RE-EVALUATION 4

OF CONCRETE MASONRY 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 walls in r.uclear power plants.

Direct reference to building code criteria was not used for the following reasons:

1) The definition of the magnitude of seismic loads in building cc 2s is different than that usPJ in nuclear power plants.

In 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.

2) Building code allowable stresses do not consider two levels of earthquake ground motion and the magnitude of the ground motion included in the building code design spectrum is not explicit.

3) Factors such as damping, analysis procedures, effect of attached equipment, two levels of allowable stresses, operability and frequency variations are not considered in building codes.

Thus the specification was developed to address the problems unique to nuclear power plants.

i 2.0 GOVERNING CODES As noted in Sec. 1 the specification covers most of the factors unique to nuclear power plants.

Items not explicitly covered by the specificaticr.

will be governed by the American Concrete Institute " Building Code Requirements for Concrete Masonry Structures".

ACI-531(29).

This code incorporates most of the recent research data available on concrete masonry.

1

3.0 LOADS AND COMBINATIONS These are consistent with the original struct7ral 1

1 design criteria for the Point Beach plant.

4.0 MATERIALS

The project specifications indicate that materials used for the performance of the work were originally specified to meet the requirements given in this section.

5.0 DESIGN ALLOWABLES The design allowable stresses given in Tables 1 and 2 are based on f', the prism compressive strength, m

for a

the mortar compressive strength or f the steel yield y

strength.

The mortar con.pressive strength is based on

(

{

the minimum specified compressive stren!'.h of ASTM C-270.

The concret, block unit comprussive strength is based on the applicable ASTM Standard - ASTM C-90 for hollow units.

The steel yield strength is based on the specified grade of the steel.

The prism compressive strength f'm is based on the specified values given in Table 4-3 of ACI 531-79.

This Table provides a conservative estimate of f', based on the mortar and concrete block unit compressive strengths.

The minimum 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 Table 1 and 2 follows.

2 l

4 l

5.1.1 AXIAL COMPRESSION (Reinforced and Unreinforced) 7 1

1.

l

- The following discussion of test results has been extracted from the cormentary to the N.CMA Specification for the Design and Construction I

I of Load Bearing Concrete Masonry.

The objective was to develop reasonable and safe engineering design criteria for nonreinforced concrete masonry based on all existing data.

i A review in 1967 of the compilation of all available test data on compres-j sive strength of concrete masonry walls did not, according to some, provide a suitable relationship between wall strength and slenderness ratio.

From

)

a more ret.ent analysis, it was noted in many of the 418 individual pieces of data that either the masonry units or mortar, or in some cases, both units and mortar, did not comply with the minimum strength requirements established for the materials pemitted for use in " Engineered Concrete k

Masonry" constru: tion.

Accordingly, it was decided to re-examine the data, discarding all tests which included materials that did not comply with the following minimum requirements:

Material Comoressive Strength Solid units 1000 psi I

Hellow units 600 psi (gross)

Mortar 700 psi Also eliminated from the new correlation were walls with a slenderness ratio of less than 6; walls with h/t ratio less than 6 were considered to be in the category of " prisms." For evaluation of slenderness reduction criteria, only axially loaded walls were used.

The data that was available consisted of tests on 159 axially loaded walls with h/t ratic ranging between 6 and 18. With this as a starting point, the data were analyzed assuming that the parabolic slenderness reduction function, (1'- (40t) I' is valid.

.lk Basic equation used to evaluate the test data was:

3

f

{

jt C f;(1-(40t))

II)

=

g f test C x S.F.

(2)

=

g fy(1-(40t))

K (3)

C, x S.F.

=

where f'

= Assumed masonry strength, net area, based on strength of units f

= Net area compressive strength of panel test S.F.

= Safety factor

((

C

= Strength reduction coefficient g

h

= Height of specimen, inches t

= Thickness of specimen, inches Net area used in the above fonnulae is net area of the masonry, and does not distinguish 'between type of mortar bedding.

In the evaluation, 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

{selectedandgaveaminimumsafetyfactorof3.

Accordingly, the K values were listed in ascending order and the value satisfying the above conditions was K =.610 for the 159 tests as seen from Table 3.

Therefore, from equation (3):

4 t

1

C,x 5.F.

=r

(

C, x 3

= 0.610 7

1 C = 0. 610 = 0. 205 i

0 3

1 4

~

This value, 0.205, agrees very closely with the coefficient 0.20 1

which had been used for a number of years with reinforced masonry design.

]

An analysis of the safety factors present with the formula:

f, 0.205f; (1 - (4gt)3) h

=

t indicates the following:

, Safety factor greater than 3 is available in 93% of the tests; greater-than 4 in 51% of the tests; greater than 5 in 15% of the tests, l.

and grea.ter than 6 in 5% of the tests.

In ACI 531 the factor of 0.20 was increased to 0.225.

The recommended l ('(

value of 0.22 for unfactored loads has factorr of safety comparable to those given above.

Doubling this value for the factored loads was 1

deemed reasonable and gives a factor of safety of 1.5 for 93% of all j

tests performed.

Although the derivation given is for unreinforced walls the same values are recommended for reinforced walls, 4

e

(

5 r-e.+y yr.

p

-M-

+

~

i-

-ee s,,mae

-.-+-u---

m-..

0}

M C

Based on f ornuIs (2), "K" f actors were calculated for all of the test specimens as listed in the following tabic:

i TABLE 3 4

I Concrete Masonry Units I

!!or t a r 11all s i

Strength, Strength, Percent psi, net Str.,

psi, net

/

n.

fE, psi psi.Beiding h/t f est fMCf K S.F.

Ref.

Solid arca t

~

. -: s 1

63 1160 980 1180 Full 6.0 750. 97S

.798 3.E3 63 1160 980 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 980 900 FS 6.0 555 970

.568 2.83 63 1200 1000 1230 Full 6.0 060 995

.863 4.30

63 1200 1000 0 730 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. 2 5,'

((

63 1320 1060 S10 Full 6.0 970 1055

.918 4. 5 8

63 1320 1060 S10 FS 6.0 780 1055

.738 3.69 !

63 1160 980 1080 Full 6.0 800 97E

.818 4.0S i 63 1160 980 10SO Full 6.0 670 978

.686 3.42 :

I 63 1810 1275 1270 Full 6.0 940 1270

.739 3.67

! 6.0,

'O 1810 1275 I1270 Full 940 1270

.739 3.67!

63 1505 1150 1670 Full I 6.0 825 1145

.719 3.60

63 1505 1150 1670 Full 6.0 820 1145

.715 3.57l j

63 1240 1020 980 Full 6.0 1010 1015

.993 4.95 1 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 880 Full 6.0 940 1225

.766 3.81 -

63 1380 1090

' 1730 Full i 6.0 1000 3085

.920 4.58 '

63 1380 1090 1730 Full [ 6.0 1010 1055

.930 4.63 '

63 17E0 1262 1870 Full 6.0 1450 1257 1.152 5.75 63 1780 1262 1870 Full 6.0 1570 1257 1.24S 6.22 43 3300 1790 1230 full 86.0 1560 1782

.874 4.36 43*

3300 1790 1230 Full ! 6.0 1730 17S2

.969, 4.84.

70 1645 1208 11140 Full j 6.0 1000 1200

.830 4.15 70 1645 _ 120S

!1140 Full 16.0 1220 1200 1.013 5.06 E

63

.;09 450 l3140 Full 6.0 303 455

.664 3.30

Full,!6.0 63 509 458 1610 295 455

.646 3.21

63 509 45S 1060 Full I 6.0 295 455

.646 3.21

(

63 840 756 3140 Full i 6.0 532 753

.706 3.52 :

63 S40

?$6

'1610 Full l 6.0 5/.0 753

.716 3.5E a

63 840 756 l1060 Full j 6.0 505 753

.670 3.33 63 875 788

13) 0 full 6.0 138 785

.558 2.79 -

6

i

! Tf :: ?'N.

'?

Cone r. : e **,ror.v" Ve f t r l

Mor:sr l

U:11r i

j h Strent,th,.

l S t r er:; : h,

l l k Percent psi, net Str..

psi, net

---f4, psi psi _ Bedding h/t f c.e.,_. t_

fA C r.

S.F.

Ref.

Solid crea 8

63 875 7ES 1610 Tull 6$0 430 785~.547 2.74 I

1 63 675 70'd 1050 full 6.0 500 705 1.637 3.17 i

63 1080 940 3140 Tull 6.0 605 936

.646 3.22

~

63 1030 960 1060 Full 6.0 765 936

.817 4.07 l

63 10S0 940 1610 Full 6.0 715 936

.763 3.81 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 1230 1015 -

1060 Full 6.0 1110 1010 1.097 5.46 l

63 1410 1105 3140 Full 6.0 1140 1100 1.030 5.16 l

63 1410 1105 1610 Full 6.0 985 1100

.893 4.45 1

63 1410 1105 1060 Full 6.0 1030 1100

.935 4.66 i

63 1520 1157 3140 Full 6.0 660 1152

.572 2.85

]

63 1520 1157 1610 Full 6.0 740 1152

.642 3.20 63 1520 1157 4780 full 6.0 830 1152

.719 3.58 I

63 1860 1295 3140 full 6.0 1476 1290 1.143 5.70 1

63 1860 1295 1610 Full 16.0 1539 1290 1.192 5.94 4

62 1860 1295 1060 full 6.0 1365 1290 1.05S 5.27' 63 2510 1554 3140 Full 6.0 369S 1550 1.096 5.47 63 2510 1554 1610 Full 6.0 1365 1550

.881 4.39' 4

63 2510 1554 1060 Full 6.0 1325 1550

.856 4.27 1

';(

63 3030 1710 3140 Tull 6.0 2222 1705 1.304 6.50 l I

l1610 full 6.0 2222 1705 1.304 6.50 63 3030 1710 63 3030 1710 1060 Full 6.0 1984 1705 1.164 5.80 l

i 63 3740 1923 Full 6.0 1857 1918

.969 4.82

,3140 63 3740 1923 1610 Full 6.0 2523 1918 1.316 6.56 j

63 3740 1923 4780 Full 6.0 2317 1918 1.209 6.03 l l

63 6640 2400 3140 Full 6.0 3587 2392 1.499 7.48 :

I 63 6640 2400 11610 Full 6.0 3856 2392 1.612 8.04 i 63 6640 2400 l4780 Full 6.0 5031 2392 2.102 10.49 !

l 12a*

100 1333 1257 2562 Full 7.0 1140 1254

.910 4.13 100 1388 1640 3017 Full 7.0 1358 1635

.830 4.57 l j

100 1892 1653 2317 Tull 7.0 1469 1846

.795 4.52 l 100 1923 1630 2153 Full 7.0 1394 1625

.058 4.29 :

100 250S 2390 2427 Full 7.0 1947 2380

.817 4.56 :

100 2529 2630 2347 rull 7.0 2151 2620

.820 4.63 l 100 2545 2130 2143 Full 7.0 1930 2120

.909 4.17 100 2610 2220 3195 Ful) 7.0 207E 2210

.939 4.71 100 2678 2030 !2322 Full 7.0 1832 2020

.905 3.?9 i Full 7.0 1310 2200

.621 4.10 i 100 4474 2210 l2792 l

100 4474 2540 215'.

Full 7.0 2157 2530

.937 4.09 l l

t tests in j

f E val ue s. f ro:. thle. reference ucre determined frora pri:2

(

stead of anguraed values.

7 cst recults r;ultiplied by fsetor of 1.2'1

.i.

i 7

i

M L.2

> Q.:.'u-: .I l Concrete lhsonrv Unt:s l

c r t w 1:a l l:,

l {

Strength, Streur,th, l'c r c en t p t. i, ne:

Str., p;i, net fE. psi psi Eeddir:g h/t f ff C 1: S.F. };c f. Solfd arca test 62 25'.7 1556 1100 rs 9.0 1241 15k0 .007 4.05 5 - 62 1886 1305 1400 FS 9.0 1153 1290 .E94 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 3.78 62 2136 1405 1400 FS 9.0 1128 1390 .812 4.07 62 1773 1260 1400 FS 9.0 1088 1245 .873 4.38 62 1298 10'9 1400 FS '9.0 854 1037 .823 4.14. 62 1241 1031 1400 FS' 9.0 685 1010 .67S 3.41 l 62 1612 1196 1400 FS 9.0 991 1180 .838 4.20l 62 1805 1273 1400 FS 9.0 1008 1260 .864 3.78jl 4.33 62 1491 1146 1400 FS 9.0 854 1133 .754 62 1038 944 1400 FS 9.0 629 933 .673 3.38 62 1918 1318 i 1400 FS 9.0 1072 1302 .822 4.12 1598l1400 62 1169 985 'FS 9.0 605 975 .621 3.12 45 2655 1400 FS f9.0 989 1578 .626 3.15g 62 1088 944 1400 FS 9.0 564 933 .604 3.03: 62 1290 1045 1400 FS 9.0 701 1032 .678 3.41 62 1999 1350l1400 FS 9.0 1104 1335 .826 4.16 62 1862 1296 1400 Full l9.0 1378+ 1280 1.075 5.446 62 967 870 1400 Full j9.0 758 860 .851 4.42 62 1967 1338,1400 Full l9.0 1241 1220 .933 4.72 1463!1400 i ' 'S ' 9.3 122S 1450 .849 4.27 5 57 2280 F 67 1917 1318!1400 FS 9.3 S36 1302 .642 3.23l 67 1380 1090i1400 FS l 9.3 724 1078 .672 3.37 67 1902 1312i1400 FS ' 9.3 1223 1300 .943 4.74 67 1246 102311400 FS l 9.3 739 1010 .731 3.67 57 20S7 1386!1400 FS

9.3 1193 1370

.S71 4.38 l 9.3 57 20S7 13S6 l 830. FS 1298 1370 .948 4.76l 57 2385 1505 l 1400 FS l 9.3 719 1485 .484 2.44 57 2385 1505 i 1400 FS 9.3 789 14SS .530 2.67 57 2385 1505!1400 FS ' 9. 3 1105 1485 .743 3.74, 57 2385 1505 ! 1400 FS j 9.3 1140 1485 .766 3.851 l 1 39 1590 1187!1130 Full i 9.5 SSS 1170 .756 3.79 l '.5 39 1590 1187i 1010 Full 1000 1370 .S53 4.28 39 171C 1238,1070 Full l 9 ', 949 1220 .777 3.C9 39 1718 1238 ', 040 Full i 9.5 910 1220 .745 3.738 i I .I s 8

_- =. O fff: n D ff? OW n k- ' W d I TAU.i. j (Co. inu.-") I Conc r et e !!.r onry l'ni t r. !

r:::

D12 e }g S t r ent, t h. Stren,.th, is Percent psi, net Str.. psi, net fE, psi psi Ecdding h/t f fyC F S.F. Ref. Solid-crea test i 1 ~ 63 1159 9SS 11F.0 Fuli 14~. 3 683 940'.726 3.62, .1139 9G5 14.'. 0 Full ..3 690 940:.734 3.64, 63 63 1159-985 1440 Full 14.3 738 940 .784 3.918 63 1159 985 1060 FS 14.3 532 940 .565 2.S2 63 1159 985 900 FS 14.3 563 940 .599 2.98 63 1159 985 1920 FS 14.3 563 940 .599 2.98 l i 63 1206 1020 1230 Full 14.3 738 974 .758 3.80 63 1206 1020 730 Full 14.3 683 974 .702 3.51 1 63 1206 1020 1130 Full 14.3 746 974 .765 3.83l 63 1206 1020 960 FS 14.3 571 974 .5S6 2.94 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 l 63 1317

1080, 880 Full 14.3 905 1030

.877 4.38 j 63 1317 1080 750 Full 14.3 1063 -1030 1.030. 5.14 63 1317 1080 810 Full 14.3 929 1030 .901 4.49 63 1312 1080' 1020 FS 14.3 714 1030 .692 3.45 t 63 1317 1080 1020 FS 14.3 667 1030 .647 3.23 3 63 1159 985 1120 Full 14.3 579 940 .616 3.07 63 1159 985 1150 Full 14.3 635 940 .675 3.37 \\ 63 1159 985 1080 Full 14.3 635 940 .675 3.37 ( 63 1810 1274 1270 Full 14.3 873 1218 .717 3.541 63 1810 1274 940 Full 14.3 881 1218 .725 3.58l 63 1810 1274 1120 Full 14.3 817 1218 .671 3.32j 63 1508 1153 1380 Full 14.3 706 1100 .641 3.17! 63 1508 1153 1380 Full 14.3 746 1100 .677 3.34! 63 1508 1153 1670 Full 14.3 643 1100 .5S4 2.88 ! 63 1238 1025 '1920 Full 14.3 833 978 .851 4.24i 4.09 '! l 63 1238 1025 980 Full 14.3 802 978 .819 63 1238 1025 1280 Full 14.3 817 97S .835 4.16 63 1714 1230 800 Full 14.3 1111 1172 .946 4.73i 63 1714 1230 800 Full 14.3 1127 1172 .959 4.79 3 4.59! 63 1714 1230 750 Fuli 14.3 1079 1172 .918 63 1381 1090 11730 Full 14.3 968 1040 .930 4.64 i 63 1301 1090,2200 Full,14.3 960 1040 .923 4.61! 8 63 1774 1245 l2100 Full !14.3 1240 1190 1.043 5.21 ! 63 2253 1450 !1230 Full !14.3 936 1385 .675 3.42! 63 2253 1450 .1270 Full ' 14. 3

920 1385

.664 3.37! 70 1643 1206.11SO Full 14.3 507 1150 .701 3.55 i 70 1643 1206 11300 Full 14.3 986 115'O .857 4.33 1 , ~ 55 1273 1040 i1220 r ll. 14.3 727 993 .732 3.66l u 55 1273 1040 l1220 full l14.3 764 193 .770 3.S4l 3.93 l1 7 100 2900 1665 --1475 Full ;15.0 1250 1565 .S01 .F" ~ _ 4.S7 f 5 65 1746 1250 t1400 Full i18.0 1100 1135 .975 65 1246 1015 1400 Full j18.0 7!)5 925 .850 4.25 ; 65 1562 1175 l1400 Full l18.0 1203 1065 1.331 5.65j 9

([ 5.1.2 FLEXURAL COMPRESSION (Reinforced and Unreinforced) It is assur:cd tha+ masonry can develop 85% of its specified compressive strength at any section. The recommended procedure for calculating the flexural strength of a section is the war.} king stress ~ procedure, which assumes a triangular distribution of strain. For normal loads an allowable stress of 0.33 f4 has a factor of safety of 2.6 for the peak stress, which only exists at the extreme fibre of the unit and has been used in practice for many years. The recommended value for factored loads also only exists at the extreme fibre and is the value recommended in the ATC-3-06 provisions. 5.1.3 BEARING (Reinforced and Unreinforced) These values for normal loads are taken directly from the ACI code. The value recommended for ' factored loads is the value recommended in the ATC-3-06 provision. (, 5.1.4 SHEAR (Reinforced) Two major test programs have evaluated the shear strength on concrete block masonry walls. The first was performed by Schneider and his test results were used as the basis for developing the UBC, NCMA and ACI code allowable stresses for reinforced masonry. A more recent and extensive test program has been performed at the University of California, Berkeley and these results will be used as a comparison with the code allowables. The test results are shown in Figure 2 and lower bqpad values are indicated for rein-forcement taking all the shear and masonry taking all the shear. These are compared to the allowables recommended for unfactored and factored loads in Table 4. 10 e

For the unfactored loads the factor of safety varies from 2.22 to 3.0. { For the factored loads the factor of safety varies from 1.20 to 1.76. The ductility indicator associated with stress levels for the factored , loads is of the order of 3 which provides an added factor of,' safety. i ~ Table 4: Comparison of Test Restuls and Code Allowables 1 Test Tests Tests Description S U Results S U Masonry Takes Shear M/Vd = 1 0.9ff;) 1.5ff; 2/f; 2.22 1.33 M/Vd = 0 2.0}fy 3.4ff; 5 /fy 2.50 1.47 Reinforcement Takes Shear M/Vd = 1 1.5/f; 2.5gf; 3ff; 2.0 1.20 M/Vd = 0 2.0/f; 3.4ffy 6 gf; 3.0 1.76 d o 11

i Lower Bound Ultimate with Horizontal Reinforcement Lower Bound Ultimate with no Horizontal Reipf orcement Code Allowable with no upper limit. Reinf o,rc ecient takes shear Code Allowable with no upper li=it. Masonri take= shear 9 No llorizontal reinforec=ent O "-32 it rizontal reinforcement 6 >.3% 11orizontal reinforcement 8%~ O O O 9 8 a 6h 9 m 0 s a: E ^ ~ 3 4 fm O% 1 w g . g.i t ~. y ~ O a + ' ~. 2 D 2jfm , _, " ~ * - - wo I! ~ . - _. " " - ~ ~ ~ * - w>< v I 1 I 0.5 I.0 2.0 4 lir.IC11T TO WIDTil RATIO 0.25 n.5 1.0 M/vn 3 6 Figure 2 4-( 12 ,w.

5.1.5 SHEAR (Unreinforc'ed) ~( IfiTRODUCT10fi 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 complicate 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 depending on the panel to transmit building shear forces. This forced drift or displacement results in shear stresses and strains, but because of the complex interaction between the panel and the ( confining structural elements strain or displacement is a more meaningful index for qualifying the in-plane performance of the panel. The area of in-plane strains is being addressed in another comittee report. The most extensive review on shear strength literature appears to have been done by Mayes, et al, and published in Earthquake Engineering Research Center Report EERC No. 75-15 wtiich 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

2 3 The shear value of 0.9 y provided by the ACI-531-79 code for reinforced masonry appear to be reasonable basis on which to proceed with the reevaluation program. This value appears to ( conservatively bound the actual expected shear strength of' concrete 13

A sumsry of several different sources for shear ( block masonry. stress-design values is shown by Table 5. An increase in these allowblevaluesforthere-evaluationprogramof1.35/f'for severe loading conditions appears warranted. Any further increase -at this time without further substantiation and review iskot seen as advisable. DISCUSS 10t! 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 Construction of Load-Bearing Concrete Masonry" .5 and the American Concrete Institute Standard " Building Code Requirements for Concrete Masonry Structures" (ACI-531-79). 2 3 No apparent tests are traceable to the origin of the Uniform Building Code (UBC) chapter 24 on " Masonry."' ~ Those tests performed to substantiate the NCMA values are ,,-( primarily performed by the National Bureau of Standards (NBS) on full size (4 ft by 8 ft, and 8 ft by 8 ft) test panels. These tests were performed by Whittemore, et al and Fishburn!' within the period 1939 to 1961. The Whittemore tests were done, as usual in that period, utilizing a hold down detail and thereby introducing a clamping or compressive stress within the assemblage. A number of studies have shown that compressive stresses affect the shear i strengtn significantly. The Fisnburn tests, utilize a racking configuration with the testing being performed on the panel in its original laid up position. A load setting up principal tension stress causing failure is an accepted measure of shear stress determination by the American Society of Te. sting Material for brickwork.11 The test results from the above references used by NCMA are shown on Table 6. The principal tests that seem to formulate the ACI 531 basis are the tests perfomed on concrete masonry piers for Masonry 1 Research of Los Angeles, by Schneider.12 These tests had a system for removing the compressive load on the specimen being loaded by 14 s

shear and were set up to vary the a/d (M/Vd) ratio and measure this { effect on a parametric basis. The two predomina.t failure modes of' a masonry panel under shear are diagonal tension (causing a "splittinn" failure) and shear bond -(causing a " joint separation" failure) or some combinatioIT of these two effects. The theory behind these were elaborated on by Yokel et al.28 The parameter of normal stress and its effects on a shear strength, which was also reviewed by Yokell' and Mayes,2", has been 2 demonstrated to be consequential on the determination of actual shear stress capability. This parameter is not identified, today, by any of the codes,6,6,is,25 shown in Table 5. 2 It is expected that under zero or small compressive loads the predominate shear failure will be by the shear bond mode of failure. Tests which have been done with regard to the determination of.ioint separation were performed by Copeland and Saxer,17 as well as Hamid, et al.18 These tests are, by their nature, extremely sensitive to normal stress and consequently do relate the effects of normal stress on permissable shear values. This relationship is shown on Table 5. It is of interest that there appears to be good correlation between these tests on the shear strength with zero nomal stress. The Applied Technology Council (ATC) is presently reviewing a formulation for increasing th.e shear stress as a function of nomal stress. This formulation is developed to coincide with their present permissible shear stress of 12 psi and is consistent with the UBC's fundamental direction as a design code, forcing reinforcing for seismicly designed masonry structures. As a practical matter, walls subject to.the conditions of confinement will experience large compressive loads - although these are difficult to detemine. Compressive loads for the most part, imparted by boundary conditions and behavior of the building E frame are ignored in the evaluation of the masonry panel. If these normal stresses are added the shear resistance would be increased. This implies a conservatism on the allowable shear value when one assumes this value as chosen on the basis of zero I 15

i On this basis, and the tests results discusscd, int normal stress. ( shear value of 0.9/f; chosen by the ACI code ap;, ears to be justifiec and should be established as a reasonable basis by which to proceed 7 with the re-evaluation. Out of plane, or so called flexural shear is definediby the code as equalling 1.1/fy. The deriyation of this value is analogous to be permissible shear value of concrete, disregarding argy reinforce-ment, of 1.1/f'. Although this is somewhate different (there is no tension steel by which to determine the appropriate j distance), the actual value is a mute point since tension will be the critical value for determining out-of-piane acceptability of a flexural member. Because of the nature of the stresses, however, and the various concerns with regar'd to the correctness of interpretation of the 4 actual effects on boundary conditions as well as such conditions as: mortar properties; absorbtivity of the mortar; confinement or lack of it on the test specimen during test; arrangement and effect of actual load, it does not seem warranted to increase these stresses ( k beyond a value of 1.35/f; (1.5 x 0.9 fy). This value is consistent with an adequate margin of safety for both the full panel wall test Any specimens referenced and the shear bond values observed by test. additional increase in the shear stress values for nonreinforced masonry under extreme environmental loads is not recomended at this time. e ( 16

r T/.LLE !

SUMMARY

- UNCROUTED MASONRY Csource Date Shear Stress Remarks

) AC1-531 79 0.9/f'msq34 M/VD jg !_ 4 ) NMCA 79 34 Type M or S Motor 23 Type N Mortar Based on NES tests (circa 1939-1961) @) UBC 79 12/10* Type M or S/N Mortar

12 psi for solid units

)) ATC 3-06 78 12 Lightweight units limited to 85 percent shear value

12 + 0.200c4; 30
being proposed for co=pressive stresses between 0 and 120 psi 16

@) Masonry Proposed 1.0 ff55 ' 35 all,c 1 g f_ Society May be increased by 0.20 e (due to dead load) l Ramid, et al 79 76 + 1.070E UItimate value based on type S mortar ( 17 'opeland/Saxen 64 70 + g/crf (fitted) Ultimate value based on 2630 compressive mortar strength (1) Values based on inspected workmanship CPc = compressive stress. 2 i D e ( 17 ~

r TABLE 6 RACKING TEST DATA--NONREINFORCED CONCRETE MASONRY W4LS Ultimate Racking Mortar Ldad, psi, Net S.F. Construction Type Mortar Eedded Area Act./ Allow Ref. 8" Hollow Units N 66 2.87 7 i N 58 2.52 7 N 57 2.48 7 j 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 i N 109 4.74 10 ( 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 Unita M 108 3.18 9 M 102 3,00 9 Avg = 3.65 Range = 2.48 - 5.61 (2) From Reference 5 ) e 9 18

r LIST OT REF EENCET FOR SHEAR (Unreinforced) 1 Mayes and Clough, " Literature Survey - Compressive, Tensile, Bond and Shear Strength of Masonry," Earthquake Engineering Research Center, University of California, 1975. 2 Adh Standard, " Building Code Requirements for Concrete Masonry structures," ~ (ACI 531-79). Com=entary on " Building Code Requirements for Concrete Masonry Structures," (ACI 531-79). 4 " Specification for the Design and Construction of Load-Bearing Concrete Masonry" - NCM/, - 1979. 5 Research Data and Discussion Relating to " Specification for the Design and Construction of Load Bearing Concrete Masonry" - NCMA - 1970. 6 Uniform Building Code, Chapter 24 " Masonry" - 1979. 7 Whittemore, Stang, and Parsons " Structural Properties of Six Masonry Wall Con-structions," Building Materials and Structures Report No. 5., NBS - 1938. 8 Whittemore, Stang, and Parsons " Structural Properties of Two Buch-Concrete Block Constructions and a Concrete Block Wall Construction Sponsored by the k-National Concrete Masonry Association," Building Materials and Structures Report. 9 Whittemore, Stang, and Parsons, " Structural Properties of Concrete Block Cavity Wall Construction" Building Materials and Structures Report 21, NBS 1939. 10 Fishburn, "Effect of Motar Strength and Strength of Unit on the Strength of Concrete Masonry Walls," Monograph 36, NBS, 1961. 11 ASTM Standard Specification for Brick and Applicable Standard Testing Methods for Units and Masonry Assemblages - May 1975. 12 Schneider, " Shear in Concrete Masonry Piers," California State Polytechnic College, Pomona, California. 13 Yokel and Fattal " Failure Hypothesis for Masonry Shear Walls" - Journal of the Structural Division, March 1976. 14 "A State of the Art Review - Masonry Design Criteria" - Computech - 1980. l 15 "Jentative Provisions for the Development of Seismic Regulations for Buildings" - Applied Technology Council Chapter 12 /. - ATC 3-06-1978. The Masonry Society Standard Building Code RequircLents for Masonry Construction, First Draft. 17 Copeland and Saxer, " Tests of Structural Bond of Masonry Mortars to Concrete Block" - Journal of the Structural Division - November 1964. 18 Hamid, Drysdale, and Heidebrecht, " Shear Strength of Concrete Masonry Joints," Journal of the Structural Division - July 1979.

5.1.6 TENSION (Unreinforced) ( A. Normal to the Bed Joint A summary of the static monotonic tests performed to determine code allowable stress for tension normal to the bed joint-was given 1 _in the NCMA Specifications. Stresses for tension in flexure are related to the type of mortar and the type of unit (hollow or solid). Research used to arrive at allowable stresses for tension in flexure in the veritcal span (i.e. tension perpendicular to the bed joints) consisted of 27 flexural tests of uniformly-loaded single-wythe walls of hollow units. These monotonic tests were made in accordance with ASTM E 72. Table 7 summarizes the test results. From Table 7 the average, modulus of rupture for walls built with Types M and S mortar is 93 psi on net area. For Type N mortar, the value is 64 psi. Appl'ying a safety factor of four (4) to these values results in allowable stresses for hollow units as follows: t Mortar Type Allowable Tension in Flexure ( M&S 23 psi N 16 psi These values are consistent with those published in the 1970 ACI Committee 531 Report and which have been only slightly altered in ACI 531-79 Code. Based upon these tests the minimum factors of safey for each mortar type are: l Mortar Type Factor of Safety M 3.87 S 2.60 N 2.81 ~ To establish allowable tensile stresses for walls of solid units, the 8-inch composite walls in Table 8 were used. These walls, composed of 4-inch concrete brick and 4-inch hollow block, were greater than 75% solid, and thus were evaluated as solid masonry 20

i construction. Mo'dulus of rupture (gross area) for these walls averaged 157 psi, giving an allowable stress of 39 psi when a saf ety factor of 4 is applied. The composite wall tests in Table 8 used Type To establish allowable stresses for solid units with Type H S mortar. mortar, the mortar influence established previously for hbilow units ~ was used: E : E ; f = 27 psi 16 f The minimum factor of safety for these tests for Type 5 mortar was 2.33. Recent dynamic tests have been performed at Berkeley and the values of tension obtained at cracking at the mid-height of the walls are as follows: 13 psi; 20 psi; 23 psi; 27 psi. The recommended values have a factor of safety of 2.8 with respect to the lower bound of the static tests for the unfactored loads and are towards the lower limit of the initiation of cracking for the dynamic An increase of 1.67 appeared reasor.able for factored loads based N tests. on the static tests. ( 21

F { TABLE 7 }~LEXLT.8J., STRD CTH-SI!! OLE 1.'YTP.I W.LLS OF HOLLOU 1R;ITS-UNITOPJ' LO.iD--VERTICAL SPAN l }!ortar Type Modulus of Rupture Proportion AS'DI C 270 psi, Net Area Reference M 110 10 M 108 NOR M 102 10 M 97 10 H 95 NOIA S 94 NCMA H 91 NCFA M ,89 NCMA N 88 4 3 84 10 S 83 NOIA S 81 ' 10 S 75 NO'A f S 69 NO1 i N 67 4 N 62 4 S 60 10 N 58 4 N 45 4 0 60 10 0 41 4 ~ 4 0 36 0 36 4 0 33 4 0 32 4 0 30 10 0 27 4 4 e ~ O w I 22

TAELE b TLIXUF U STT.E :0T.-. VIF.!!C/.'. ST!.!: CC:: F.ETE '.*. C::?.Y 1.'.*.tr [* TROM TESTS AT ;;C):A 1AEClaTOT.T Ua11 Modulus of Ruoture 1:c t Max. Net 1 }!ortar ASn! Nominal Uniform Section Cross O Eedded Mortar Thickness Lead Mod lus Area, l

Area, Type

in.

Psf. in 3/ft psi psi Monovythe Ualls of Eo11ov Units M 8 85.15 80.97 61.74 88.73 87.10 80.97 63.15 90.76 M 8 8 91.00 80.97 65.97 8 94.82 M M - 8 103.35 80.97 74.93 ! 107.69 S 8 62.40 S0.97 45.24 1 69.47 5 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 i ( Co=posite Walls of Concrete Brick & Hollou CHU l i' 4 8 222.3 103.82 161.16 180.67 S S 8 219.7 103.82 159.29 178.55 l 5 8 187.2 -78.16 135.72 202.09 i S 8 228.8 103.82 165.88 185.95 i 5 8 218.4 78.16 158.34 235.77 l 5 8 213.6 78.16 162.11 ' 241.33 ! S 12 171.6 139.83 53.46 103.55 ! S 12 150.8 139.83 46.98 91.00 l S 12 156.0 139.83 l 48.60 94.14 128.66 5 12 213.2 139.83 66.42, Cavity Valls S 10 98.8 ,50.36 158.62 165.55 ! S 10 156.0 50.36 250.44 261.38 i S ' 10 88.4 48.16 141.91 154.ES i ~ S 10 119.6 50.36 192.01 200.t.0 i S 10 114.4 50.36 183.66 191.6S, 4C.16 175.30 J S1.32 ' 10 109.2 S I 50.36 233.73 243.9' : ( S 12(4-4-4) 145.6 S 12(4-4-4) 145.6 1 50.36 233.73 21 3.9* - S 12(6-7-4) 135.2 j 77.80 127.3S 146.63

S 12(6-2-4) 119.6 77.00 112.6S 329.70 '

I j __ 23 M. - r t..: ty p 'gy y:oi.v/:.;.s. s. b..:.. s.

i ~ l ( B. Tension Parallel to Bed Joints Values for allowable tension in flexure for walls supported in the . horizontal span are established by doubling the allosables in the vertical span. While it is recognized that flexural tensile sdrength of ~ . walls spanning horizontally is more a function of unit strength than mortar, it is conservative to use double the vertical span values. Table 9 lists a sumary of all published tests and indicates an average safety factor of 5.3 fer the 43 walls containing no joint reinforcement and 5.6 for the 15 walls cont.ning joint reinforcement. It is important to note that t:ie 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 4 center had an average factor of safety of 6.08 with a minimum value of 3.59. However, it should be noted that the values tested at the k points were also tested at 15 days. The results associated with the early date of testing and the use l(( of quarter point loading are difficcit to explain other than to state they 1 are at variance with all other test results. An increase in the allowable by a factor of 1.67 is recomended for factored loads. The comittee believes that the recomended values could 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 increase in other stresses for unreinforced masonry. The values recomended for stack bonded construction although at variance with current building codes (which allow zero) are thought to be reasonable values for a reevaluation program. In a test program perfomed by PCA(2) a horizor.cally spanning stack bonded wall had 2/3 the capacity of an equivalent wall laid in running bond. The recomended values are in accordance with this test data. i.e. two-thirds of the value normal to the bed joint is equivalent to 2/3 the values recomended for parallel to 5 the bed joint.

Reference:

2)PortlandCementAssociation,"i.oadTestsofPatterenedConcrete Masonry Walls, " Trowel Talk an aid to Masonry Industry,1963. 24

TLEXURAL 5!aE! Til, }IOP.120!!TAL SPA':, TAILE 9 N3:..II:iTOT.;ID C;;;C.:.E! l'ASO;;F.y 1 A1.L5 T Modulus l 5'r I02dit: of Rup:ure

ACE *[I1ICU

?.e f. r M'or:ar l psf i Ke Areo. nsi! _a Tvoe Ty:e Construction 4.13 4 N Unif or::: 127 1.2 4.41 4 Monouythe B", 136 141-4 4.13 N -Hollow, 3-Core 127 132 '4 5.50 N 169 176 N 5.63 4 173 180 4 4.00 N 128 4 123 5.13 0 158 ' 164 0 4.84 4 149 155 N 5.19 4 Monovythe 8',' 160 166 N 6.28 4 Hollou, Joint 201 4 193 ; 4.8S N Reinf. 0 16 in.cc 150 156 0 6.03 4 18'6 193 0 6.59 4 203 211 6.38 4 Monowythe 8" N g 204 196 6.56 4 N llollow Joint 210 202 i 6.34 4 ( Reinf. G B in.cc 0 195 i 203 O I s I 1.81 6 8 58 6 Monouythe-8" N 1/4 pt 56 l 1.22 3B -39

1. 9 7..

6 N 61 l 63 Hollow N 1.94 6 ) 60 i 62 6 1 2.22 N 69l 71 3.00 6 N 93 ' S6 N 4.72 26 l M Center 199 i 217 4.17 26 l 8" Monowythe M L 176 l 192 4 3.59 26 Hollou, 2-Core 151 1 165 M' 4.57 26 210 135 ! 255 5.54 26 I 111 l 4-2-4 Cavity M 3.91 26 liall,, llollow f M 180 l 95 M ' Units B" Monouythe M 159 l 173 3.76 26 i i73 3.76 26 l 191 208 4.52 26 l Hollow 2-Core ! M 159 P Joint Kc. O U"oc M f 1 l 159 l 300 6.52 26 Hollou Units ticd M i 159 1 300 i 6.52 26 4-2-4 Cavity ofi M i 159 l 300 6.52 26 v/ Joint ke. 6 B"oc :: i l I i i 1 i l 25 l l

.= l T/F_t C' (---'-- Loiulus ( Mortar Loadint of Rupture S.F. Construction Type Type l psf

Nc: Arec, psi Act./313cy p,, f,

4" Hollou N Center 13E ~ 365 11.41 25 - Mono.ry:he N 157 415 -:12.57 25 N 101 268 8.38 25 ~ 8" Hollou M 268 202 4.39 25 - Monowythe M 314 237 5.15 25 M 314 237 5.15 25 S" Bollow N 277 210 6.56 25 Monowythe N 314 g 237 7.41 25 N-314 237 7.41 25 B" Bollou O 259 195 6.09 25 Monowythe O 277 210 6.56 25 0 277 210 6.56 25 i I 8" Uellow M 268 202 4.39 25 l Monouythe M 297 224 4.87 25 l 1! 277 210 4.56 25 1 l { 8" Hollow N. 277 210 6.56 25 I Monowythe N 259 I 195 6.09 25 N 297 224 7.00 25 8" Bollou 0 360 271 8.45 25 l Monouythe O 297 8 224 7.00 25 0 268 i 202 6.31 25 12" Hollou N 352 [ 142 4.44 25 t!onouythe N 314 l 127 3.97 25 l N 333 134 4.19 25 [ I J J e 9 1" (. I 26 'm-- W ^

i 5.1.7 SHEAR AND TENSILE B0 tid STRENGTH OF MA50iRY COLLAR JOINT The collar joint shear and tensile bond strength is a major factor in the behavior of multi-wythe masonry construction, particularly with resnect to weak axis bending. A widely stated position is that for composite construction the collar joint must be completely filled with mortar. However, even if this joint is filled, there must be a transfer of shearing stress across this joint without significant slip in order for full composite interaction of the multiple wythes to be realized. Since the cracking strength, moment of inertia, and ultimate flexural strength, of the wall cross section are significantly influenced by the interaction of multiple wythes, it is crucial to establish the collar joint shear bond strength. The only applicable published data on the shear bond strength of collar joints is that determined by Bechtel on the Trojan Nuclear Power. Plant. A number of 8/e" collar joints were tested and the accept'ed NRC allowable for the shear bond strength was 12 psi. Based on this infomation 12 psi is the reconnended value for factored loads. There is conflicting data available on the relationship between the shear and tensile bond strengths. In most tests performed on mortar bed joints (couplet tests) the shear bond strength was approximately twice the tensile bond strength. In a more recent method of evaluation by means of centrifugal force the shear bond strength was found to be 60% of the tensile bond strength. The authors of the report consider the test procedure to be an improve-ment over present methods since joint precompression is essentially eliminated as a result of the testing procedure. Because of the conflict in the test data the committee recomended that the values for tensile bond strength be the same as for shear bond. 2 Unless metal ties are used at closely spaced intervals (less ~ than 16 inches on center) it is recomended that their contribution to shear and tensile bond strength, be neglected. i 27

Reference:

{ (1) Hatzinkolas, M., Longworth, J., and Wararuk, J., " Evaluation of Tensile Bond and Shear Bond of Masonry by Means of CentrifugalForce,"AlbertaMasonryInstitute,[Edmonton. Alberta. ~ 5.1.8 BOND (reinforced) Values for bond stress are taken directly from the ACI Code. Due to the sensitivity of workmanship, degradation under cyclic lead and the implications of a bond mode of failure it is recommended that these values be increased by 33 1/3% for factored loads. 5.1.9 GROUT CORE TENSILE STRESS The tensile value recommended for the grout core tensile stress is taken from ACI 318 for concrete with a factor of safety of three. 4 An increase of 1.67 was deemed reasonable for the factored loads. 5.2 DAMPING The damping values for unreinforced walls are based on judgment and include a differentiation for the OBE and SSE force levels. This is based on the premise that damping increases as the stress level increases. The damping values for reinforced walls are cased on the accepted values for reinforced concrete. There is no test data available in the literature to validate or refute these damping values. 2 6.0 ANALYSIS AND DESIGN 1 E 6.1 STRUCTURAL RESPONSE OF UNREINFORCED WALLS 4 6.1.1 OUT OF PLANE EFFECTS The steps given in this section provide a logical conservative evaluation methodology to determine the stress levels in a masonry wall 28 c-. 3 y -w-.

[ l ({ subjected to out of plane forces. The first two steps provide a lo.;e-bound estimate on the frequency of the wall since it assumes the wall spans in only one direction. For a wall with two or mora sides capable ofactingasboundariesthestressesresultingfromonefayorbeam action will be cons,ervative compared to those obtained from a more rigo,7us plate analysis. If the stresses resulting from the analysis exceed the allowable stresses or the wall contains significant openings the beam analysis is not appropriate and the full effect of the actual boundary conditions must be accounted.cr in a plate analysis. For walls with openings it is recommended that a finite element plate analysis be performed to correctly model the effect of the opening. For walls without openings either a finite element analysis can be performed or standard test book formulae for plates may be used. If a multimode analysis is not per-formed it is recommended that the moments and stresses be increased by 1.05 to account for higher mode effects. Many parameter studies have { been performed that indicate that in most cases the first mode of ~ { vibration contributes 98% or more to the total response of the wall. Thus the 1.05 factor is considered adequate. 6.1.2 FREQUENCY VARIATIONS 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. If the frequency of a wall falls on the low frequency side of the amplified region of the response spectrum adequate provisions are included to ensure that the determination of the stress in the wall is conservative. 29 ,y-m-

Il 6.1.3 IN PLANE AflD OUT OF PLANE EFFECTS ( The plant FSAR prcvides for the design of a two-direction (one horizontal and one vertical) earthquake. The provisions-of this section are consistent with the FSAR. The vertical comp 3nent of motion is not included in the analysis procedure because the positive effect of the dead load on bed joint stresses is not included in the evaluation criteria. It should be noted however that the effect of vertical acceleration is included in determining the pipe and equipment loads on the wall. 6.2 STRUCTURAL RESPONSE OF REINFORCED fM50NRY WALLS 6.2.1 OUT OF PLANE EFFECTS The com.ents in Sec. 6.1.1 are applicable to the uncracked condition of a reinforced wall. If the wall cracks in either the ( vertical or hori ontal direction cracked section properties of the ~ ( wall are used to detemine the frequency of either the beam or the plate. If a plata analysis is perfomed an orthotropic analysis must be perfomed in which different section properties in the horizontal and vertical directions are used. 6.2.2 EQUIVALENT NOMENT OF INERTIA 6.2.2.1 CRACKED CONDITION The recormiended value of I is taken from ACI 318. The fomula e was developed for slender columns and was considered to be appropriate for the out of plane analysis of masonry walls. The fomula was checked against the test results of Dickey and Mackintosh (I) and reasonable agreement was obtained. It should be noted that if this i fomula is used it should be used over the total length of the wall and not over the cracked section. The fully cracked section moment of inertia provides a lower limit and can be used over the cracked section of the wall. It is ( very conservative to use it over the full length of the wall. 0 1

i . ([

Reference:

(1) Dickey .W. L., and Mackintosh, A., "Results of Variation of "b" or Effective Width in flexure in Concrete Block Panels," Masonry Institute of America,1971. - - 6. 2. 3 FREQUENCY VARIATIONS See Sec. 6.1.2 for comments. 6.2.4 IN PLANE AND OUT OF PLANE EFFECTS See Sec. 6.1.3 for connents. 6.3 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. ({ 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. 6.5 IN PLANE EFFECTS Load bearing structural masonry walls shall be evaluated on an allowable stress basis. The shear stress on the wall is determined 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. 1. It does not carry a significant part of the building's story shear or moment. 2. It does not significantly-modify the behavior of adjacent ( structural elements. 31

F O (

n other words, the expected behavior of the building must be substantially the same whether such walls are present or not.

In-plane effects may be imposed on these masonry walls by the relative displacement between floors during seismic events. Ho ever, ~ the walls do not carry a significant part of the associaI.ed story shear, and their stiffness is extremely difficult to define. In addition, since the experimental evidence to date demonstrates that the apparent in-plane strength of masonry walls depends heavily upon the in-plane stress boundary conditions, load or stress on 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 the gross shear strain of walls is a reliable indicator 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 IM of a wall's width or height. Cracking along the interface between. a block wall and steel or concrete members does not limit the integrity of the wall, and is g not addressed here. The gross shear strain is defined to be: ( 8= where: '6 = strain A = 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: 1. Unconfined Walls - not bounded by adjacent steel or concrete primary structure. Significant " confining" stresses cannot be expected. 2. ConfinedWalls-at3 minimum,b5undedtopandbottomor bounded on three sides. For unconfined concrete block masonry walls the works of Fishburn (2) and Becica (1) yield an allowable shear strain as defined above of 0.000). ( It should be noted that Fishburn's test specimens were 15 days old, on average. 32 6 e e

r ( For confined walls, tne most reliable data appears to be Inat of Mayes et al (4). In static and dynamic tests of masonry piers (con-fined top and bottom) varying block properties, mortar twoperties, reinforcement, vertical load and grout conditions, signi,ficant ~ cracking was initiated at strains exceeding about Y = 0.001. It 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 Bertero (3) perfomed a series of cyclic tests to failure and found excellent correspondence with a non-linear analysis in which the behavior of an infilled frame prior to cracking is deter-mined by an equivalent diagonal strut. While the equivalent strut technique has been used by many investigators to study the stiffness ( and load-carrying mechanisms of infilled frames, Klingner and Bertero found that the quasi-compressive failure of the strut could be used to 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 ) =1+ 1000B/H in which B = wall width H = wall height assuming E = 1000fln In sumary, the recomended value for pemissible in plane strain for service loads in unconfined walls is: )(= = 0. 0001 1 and in confined walls ( = 0. 001 For factored loads these strains may be increased by 1.67. 33 3

r C For non-load bearino walls that are subjected to both in plane '( shear stresses and interstory drif t effects thb combination equation specified limits the combined effect such that the sum of the propor-tion of stress induced by each is less than 1. The compiexity of this type of loading has not been validated by tests and the ' procedure reco, mended is deemed reasonable. m h e ( t. a 34

r-e o $E.~ t'll.'!/Ea'//!.'Iriaj,. ~ d l 4 f }. 4 ?. f> f t 6 ) h 5 4 y E h k ..,m...... i v.,,.. in win........i......- t confined confined .r.wie n w w erp.e r '~r.n n.</~.!,n.n p.~es,c v f i il / /* p k ~ I ,M h2 Y A /' M t E4 v. 2 h b 6 p V,e p..e.i,.a,.x.'.o x.s.~ t x,..,..,i. :,,,./..vi..r.,ai 4 g. confined . confined k p Fi. mare Exmpics Defininn W " Confined" and, f' " Unconfined" Walls .Jpi p', E w,,.,,+. c.. unconfined ( ~ ( 35 y <

4' REFEREf1CES 1. Becica, I.J. and H.G. Harris, " Evaluation of Techniques in the Direct Modeling of Concrete Masonry Structures " Drexel University Structural _Nodels Laboratory Report No. M77-1, June 1977. 2.~ F,ishburn, C.C. "Effect of Mortar Properties on Strength of Masonry," National Bureau of Standards Monograph 36 U.S. Government Printing Office, Nov.1961. ~ 3. Klingner, R.E. and V.V. Bertero, " Earthquake Resistance of Infilled Frames," Journal of the Structural Division, ASCE, June 1978. 4. Mayes, R.L., Clough, R.W., et al " Cyclic Loading Tests of Masonry Piers," 3 volumes; EERC 76/8, 78/28, 79/12 Earthquake Engineering Research Center, College of Engineering University of California, Berkeley, California. 5. Benjamin, J.R. and H. A. Williams, "The Behavior of One-Story Reinforced Concrete Shear Walls," Journal oi~the Structural Division, ASCE, Proceedings, Paper 1254, Vol. 83, No. ST3, May 1957, pp.1254.1-1254.39. 6. Benjamin, J.R. and H. A. Williams, "The Behavior of One-Story Brick Shear Walls," Journal of the Structural Division, ASCE, Proceedings, Paper 17(3 Vol. 84, ST4, July, 1958, pp. 1723.1-1723.30. 7. Benjamin, J.R. and H. A. Williams, " Behavior of One-Story Reinforced Co'ncrete

f..

Shear Walls Containing Openings," Journal of the American Concrete Institute, ( Proceedings, Vo1. 30, r , November,1958, pp. 605-618. 8. Holmes, M., "StAe1 Fr . with Brickwork and Concrete Infilling," Prot _;ings of the Institution of Civil Engineers, Vol.19, August,1961, pp. 473-478. 9. Holmes, M., " Combined Loading on Infilled Frames," Proceedings of the Institution of Civil Engineers, Vol. 25, May, 1963, pp. 31-38. 10. Liauw, T.C., " Elastic Behavior of Infilled Frames," Proceedings of the Institution of Civil Engineers, Vol. 46, July, 1970, pp. 343-349.

11. Mallick, D.V. and R.T. Svern, "The Behavior of Infilled Frames Under Static Loading," Proceedings of the Institution of Civil Engineers, Vol. 39, February, 1968, pp. 261-287.

12. Smith, B.S., " Lateral Stiffness of Infilled Frames," Journal of the Structural Division, ASCE, Vol. 88 No. ST6, December, 1962, pp. 183-199. 13. Smith, B.S., " Behavior of Square Infilled Frames," Journal of the Structural Division, ASCE, Vol. 91, No. ST1, February, 1966, pp. 381-403. 14? Smith, B.S., "Model Test Results of Vertical and Horizontal Loading in Infilled Frames," Journal of the American Concrete Institute, Proceedings, Vol. 65, No. 8, August,1968, pp. 618-623. (

15. Smith, B.S. and C. Carter, "A Method of Analysis for Infilled Frames," Proceedings of the Inrtitution of Civil Engineers, Vol. 44, September, 1969, pp. 31-48.

36

F 0 0 ( 6.6 EQUIPMENT The method specified to account for the effect of equipment is conservative. Theeffectofequipmentmassisincluded(inthefre-quency calculation of the wall and thus the inertia effect of the mass of the equipment is included in the detemination of the stress in the wall. This procedure by itself may not be sufficient because it does not account for any amplification of the ec,.a r int. Thus it is recomended that the fully amplified effect of the aquipment be included by applying a static load and combining the resulting stresses with the stresses from the inertia loads. The combination shall be perfomed by the absolute sum method. Refinement to this procedure is pemitted 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 PLANE LOADS The criteria for distributing concentrated out of plane loads is taken from the Unifom Building Code and is applicable to both reinforced and unreinforced construction. The limitation on stresses for beam or one way action is specified to ensure that these are not lower than those obtained from plate or two way action. The allowable stresses for block pullout are based on the shear bond strength of a block since.this is the mode of failure for uncon-fined block pullout. The discussion given in Sec.S.I.S for the allowable values for unreinforced shear walls indicates that these values are in accordance with the available test data on the shear bond strength of concrete masonry. 7.0 ALTERNATIVE ACCEPTANCE CRITERIA E 7.1 REINFORCED PASONRY Reinforced masonry walls whicti are well anchored and supported can k undergo large ductile inelastic and out of plane flexural defomations (1). i An approximate analysis method of detemining the out of plane inelastic 37

l i seismic response is the " energy balance" technique. This analysis technique is, in essence, similar to Blume's (2) reserve _ energy technique and is analogous to Newmark's (3) inelastic setsm;c response spectrum technique.

References:

(1) Dickey, W.L. and Mackintosh, A., "Results of Variation in "b" the Effective Width in Flexural Concrete Block Panels," Masonry Institute of America, 1971. (2) Blume, J. A., Newnark, N.M. ar.d Corning, L.H., " Design of Multistory Reinforced Concrete Buildings for Earthquake Motions," Portland Cement Association,1961. (3) Newmark, N.M., " Current Trends in the Seismic Analysis and Design of High-Rise Structures," Chapter 16. Earthquake Engineering, Edited by R. L. Weigel, McGraw-Hill, 1970. k( 7.2 UNREINFORCED MASONRY An extensive test program perfomed by Gabrielson (1) on blast loading of masonry walls provides validation of the concept of arch action of masonry walls subjected to loads that exceed those that cause flexural cracking of an unreinforced masonry wall. An analytical procedure was developed to predict with reasonable accuracy the ultimate capacity of the unreinforced wal'ls tested. With a factor of safety of 1.5 the procedure is used to detemine the ultimate or collapse capacity of masonry walls.

Reference:

(1) Gabrielson, G., Wilton, C. and Ka' plan, K., " Response of Arching Walls and Ocbris from Interior Walls Caused by Blast Loading," URS Report 2030-23 URS Research Co., 1975. k 38 -}}

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