ML20077K977

Revised Masonry Wall Design (B-59),DC Cook Nuclear Plant, Units 1 & 2, Technical Evaluation Rept

ML20077K977
Person / Time
Site:	Cook
Issue date:	07/27/1983
From:	Con V, Triolo S FRANKLIN INSTITUTE
To:	Nilesh Chokshi NRC
Shared Package
ML17320A780	List: ML20077K977
References
CON-NRC-03-81-130, CON-NRC-3-81-130 IEB-80-11, TAC-42859, TAC-42860, TER-C5506-241, TER-C5506-241-R01, TER-C5506-241-R1, NUDOCS 8308030382
Download: ML20077K977 (38)

Text

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. TECHNICAL EVALUATION REPORT i MASONRY WALL DESIGN (B-59) -

INDIANA AND MICHIGAN ELECTRIC COMPANY

.E DONALD C. COOK NUCLEAD. PLANT UNITS 1 AND 2

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, 1 NRC DOCKET NO. 50-315, 50-316 FRC PROJECT C5506 i NRC TAC NO. 42859, 42860 FRC ASSIGNMENT S j NRC CONTR ACT NO. NRC-03-81 130 FRC TASK 241 k'g I 5!

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Philadelphia, PA 19103 FRC Group Leader: V. N. Con k$ Preparedfor FS Nuclear Regulatory Commission 7 Washington, D.C. 20555 Lead NRC Engineer: N. Chokshi i%

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July 18, 1983 M- Revised July 27, 1983

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'p This report was prepared as an account of work sponsored by an agency of the United States

! Government. Neither the United States Government nor any agency thereof, or any of their e -

employees, makes any warranty, expressed or implied, or assumes any legal liacility or responsibility for any third party's use, or the results of such use, of any information, appa.

'I ratus, product or process disclosed in this report, or recresents that its use by such third party would not infringe privately owned nghts.

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MASONRY WALL DESIGN (B-59) I

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INDIANA AND MICHIGAN ELECTRIC COMPANY DONALD C, COOK NUCLEAR PLANT UNITS 1 AND 2 NRC DOCKET NO, 50-315, 50-315 FRC PROJECT C5506 NRC TAC NO. 42859, 42860 FRC ASSIGNMENT 6 i NRC CONTRACT NO. NRC-03-81 130 FRC TASK 241 Preparedby Franklin Research Center Author: S. Triolo, V. N. Con 20th and Race Street Philadelphia, PA 19103 FRC Group Leader: V. N. Con Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer: N. Chokshi l

July 18, 1983 Revised July 27, 1983 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, appa-ratus, product or process disclosed in this report, or renresents that its use by such third party would not infringe privately owned rights.

1 Prepared by: Reviewed by: Approved by:

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Principal Author Project Manager

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I Date: I!I ! Date: ND Date: 7 ~ l 9 "" T 3 4

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TER-C5506-241 CONTENTS Section Title Page 1 INTRODUCTION . . . . . . . . . . . . . 1 1.1 Purpose of Review . . . . . . . . . . . 1 1.2 Plant-Specific Background . . . . . . . . . 1 2 REVIEW CRITERIA. . . . . . . . . . . . . 3 3 TECHNICAL EVALUATION . . . . . . . . . . . 4 3.1 Evaluation of Licensee's Criteria . . . . . . . 4 3.2 Evaluation of Licensee's Approach to Wall Modifications . 14 4 CONCLUSIONS. . . . . . . . . . . . . . 15 5 REFERENCES . . . . . . . . . . . . . . 16 APPENDIX A - SGEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEOIECHNICAL ENGINEERING BRANCH (SGEB] OF THE NBC) 4 iii A3d Frankun Research Center 4 w or N rw

T TER-C550 6-241 FOREWORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NBC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by the NBC. '

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1. INTRODUCTION 1.1 PURPOSE OF REVIEW The purpose of this review is to provide a technical evaluation of the Licensee response to IE Bulletin 80-11 (1] with respect to compliance with the U.S. Nuclear Regulatory Commission (NRC) masonry wall criteria. In addition, if the Licensee plans repair work on masonry walls, the planned methods, procedures, and repair schedules are reviewed for acceptability.

1.2 PLANT-SPECIFIC BACKGROUND In response to IE Bulletin 80-11, Indiana and Michigan Electric Company provided the NRC with letters and attachments (1-5] . As a results of the review of these references, a request for additional information was sent to the Licensee on July 13, 1982 [6). The Licensee has responded to this request by providing answers to all questions (7). With regard to dbe use of joint reinforcement, a set of questions was sent to the Licensee (8] to which a response was submitted [9].

According to the Licensee's responses to IE Bulletin 80-11, the information regarding the masonry walls in the Donald C. Cook Nuclear Plant Units 1 and 2 is given as follows:

1. There are no masonry walls in the containment building.

2. No safety-related equipment or piping systems are attached to or supported by masonry walls, with the exception of certain junction boxes for some safety-related conduits.

3. According to Reference 5, Attachment A and Reference 7, the following table summarizes the status of masonry walls at the Cook plant:

o Masonry walls in Class I areas 144 o Number of safety-related walls 122 o Number of non-safety-related valls 22 o Number of safety-related walls modified 34 t/J Franidin Research Center s om n ar m vamen w

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TER-C5506-241 o Walls do not have vertical reinforcement.

o Walls have running bond construction pattern.

o Dur-O-Wal was placed in alternate bed joints. Dur-O-Wal was continually installed around corners and ends were lapped 8 inches.

o Anchors were also provided at every 16 inches along the vertical edges.

o Construction materials are given below:

Compressive strength of masonry Hollow masonry units 1000 psi (ASTM-C90)

Solid masonry units 1200 psi (ASTM-C145)

Compressive strength of mortar Type N mortar (hollow units) 750 psi Type M mortar (solid units) 2500 psi Yield strength of Dur-O-Wal truss reinforcing 70 kai (ASTM-A82) 4

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2. REVIEW CRITERIA The basic documents used for guidance in this review were the criteria developed by the Structural and Geotechnical Engineering Branch (SGEB) of the NBC [10} (attached as Appendix A to this report), the Uniform Building Code

[11]; and ACI-531-79 [12] .

In general, the materials, testing, analysis, design, construction, and inspection of safety-related masonry structures should conform to the SGEB criteria. For operating plants, the loads and load combinations for qualifying the masonry walls should conform to the appropriate specifications in the FSAR for the plant. Allowable stresses are specified in Reference 12 and the appropriate increase factors for abnormal and extreme environmental loads are given in the SGEB criteria (Appendix A) .

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3. TECHNICAL EVALUATION This evaluation is based on the Licensee's earlier responses [2-5] and subsequent responses (7, 9] to the requests for additional information [6, 8]. The Licensee's criteria were evaluated with regard to design and analysis methods, loads and load combinations, allowable stresses, construction specifications, and materials. The Licensee's response to the questions contained in the request for additional information was also reviewed.

3.1 EVALUATION OF LICENSEE'S CRITERIA The Licensee has performed the reevaluation of the masonry walls using the following eriteria o Analysis was performed by working stress design method.

o For allowable stresses. ACI 531-79 [12] was used.

o Damping values used are specified as follows:

- 2% damping for operating basis earthquake (OBE)

! - 5% damping for design basis earthquake (DBE) .

o Walls were modelea as horizontal spans o Loads and load combinations are the applicable loads from the plant FSAR.

o Horizontal reinforcement (Dur-O-Wal) has been used to qualify five masonry walls.

The Licensee's responses [7, 9] to the requests for additional information [6, 8] are reviewed below:

Question 1 Describe the assumptions, modeling techniques, and procedures used in the analysis.

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TER-C5506-241 Response 1 The Licensee's response indicated that the working stress design method was used in the analysis. The walls were horizontally restrained by intersecting concrete or masonry walls and steel columns, and mortar joint was provided at the bases. At the intersection of two walls, joint reinforcement was continuous around corners, and ends were lapped 8 inches; anchors were also installed along the vertical edges at every 16 inches. The tops of the walls were not restrained. The walls were analyzed as horizontally spanned walls. It is noted that the walls have Dur-O-Wal placed in alternate bed joints and that no vertical reinforcement was installed along the vertical direction.

A review of sample calculations indicated that a beam strip with proper boundary conditions was employed in the analysis. Shear and moment distribution was obtained via dhe working stress design method. Calculated shear and moment were compared to the allowables specified in the ACI 531-79 codes. The analysis procedures are judged adequate and in compliance with the SGEB criteria.

Question 2 Specify the number of modes of vibration considered in the seismic analysis, and show how the effect of higher modes of vibration has been considered.

Response 2 The Licensee's response indicated that fundamental frequency was used to determine the acceleration. A peak acceleration of the floor response spectra was used. In addition, the damping values used were also conservative (2% for OBE and 5% for SSE). Based on these conservative measures and for all practical purposes, the fundamental mode should adequately cover the total responses of the walls. It has been found, in many cases at other plants, that the first mode usually contributes 95% or more to the total responses.

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TER-C5506-241 Therefore, it can be concluded that the Licensee's approach is satisfactory and in compliance with the SGEB criteria.

Question 3 Indicate how earthquake fotees in three directions were considered in the analysis.

Response 3 The Licensee clarified that, for seismic analysis, one horizontal earthquake force and the vertical earthquake force are considered to act simultaneoucly. This, in fact, is the licensing basis for the D. C. Cook plant. The Licensee's response is adequate and in compliance with the plant's Final Safety Analysis Report (FSAR). Therefore, it meets the requirements of the SGEB criteria.

Question 4

, Indicate how the seismic analysis accounted for variations of frequency due to uncertainties in mass, materials, and other parameters used.

Response 4 To account for variations of frequency due to uncertair. ties in mass, materials, and other parameters, the Licensee indicated that, for a typical

. wall, a range of fundamental frequencies was estimated based on 10% variation in both material mass and strength. The greatest acceleration was obtained '

from the floor response spectra and was used to determine the seismic force.

The Licensee's response is satisfactory and in compliance with the SGEB l criteria.

l Question 5 Specify material types used and provide values of allowable stresses for masonry, mortar, grout, and reinforcement.

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o e TER-C5506-241 Response 5 The Licensee provided the following information:

Compressive strength of masonry Hollow masonry units 1000 psi (ASTM-C90)

Solid masonry units 1200 psi (ASTM-C145)

Compressive strength of mortar Type N mortar (hollow units) 750 psi Type M mortar (solid units) 2500 psi Yield strength of Dur-o-Wal truss reinforcing 70 ksi (ASTM-A82)

Furthermore, the Licensee used the allowable stresses specified in ACI-531-79 (10] for the uninspected construction category. The Licensee indicated that the masonry walls were erected as per Architectural Specification No. DCC-A139-QCS, which did not require written documentation for field inspection during construction. To account for this lack of documentation, reduced allowable stresses were used in the reevaluation.

Based on a review of ASTM standards specified above and due to the fact that reduced allowable stresses were used for the uninspected construction category, the Licensee's response is adequate and satisfies the SGEB criteria.

Question 6 Regulatory Guide 1.61 allows 4% damping for the operating basias earthquake (OBE) and 7% damping for the safe shutdown earthquake (SSE) .

Provide the damping values used in the analysis and justify them if they

are higher than those allowed in Regulatory Guide 1.61.

1 Response 6 The Licensee has provided for damping values used in the analysis as follows:

- 2% dampiag for operatirg basis earthquake 1

- 5% damping for design basis earthquake.

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TER-C5506-241 These values are more conservative than those allowed in Regulatory Guide 1.61 and are therefore satisfactory.

Question 7 Provide any increase factors that may have been used for allewable

- stresses under abnormal conditions. If they are higher than those factors listed in the SGEB criteria [8], provide justification. The SCEB factors are listed below by types of stress.

Axial or flexural compression 2.5 Bearing 2.5 Beinforcement stress except shear 2.0 but not to exceed 0.9 fy Shear reinforcement and/or bolts 1.5 Masonry tension parallel to bed joint 1.5 Shear carried by masonry 1.3 Masonry tension perpendicular to bed joint reinforced masonry 0 unreinforced masonry 1.3 Response 7 The Licensee's response has provided the stress increase factors used in the abnormal load conditions as follows: ,

Axial or flexural compression 1.33 Bearing 1.33 Shear carried by masonry 1.33 Masonry tension parallel to bed joint 1.33 Masonry tension perpendicular to bed joint reinforced masonry 0 unreinforced masonry 1.33 Shear reinforcement and/or bolts 1.33 The Dur-O-Wal reinforcing was stressed to 0.9 fy Except for the increase factor for Dur-O-Wal reinforcing (to be discussed later in this section), the increase factors are satisf actory since they are equal to or lower than those allowed by the SGEB criteria.

Question 8 Indicate the boundary conditions used for analyzing the masonry walls and provide justification for those boundary conditions.

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TER-CS506-241 Response 8 Regarding the boundary conditions used in the analysis, the Licensee indicated that the walls are restrained at their bases and along the vertical edges. Dur-O-Wal truss reinforcing was installed continuously around corners, and ends were lapped 8 inches. In addition, anchors were provided at every 16 inches along the vertical edge. The analyzed walls were assumed to be simply supported along the vertical edges and free at the top and base.

The Licensee's response is considered adequate and satisfactory.

Question 9 Indicate if the cracking of sections of the walls was given proper consideration in the analysis.

Response 9 The Licensee indicated in Reference 7 that the tensile stresses existing in the masonry walls are lower than the tensile capacity of the mortar in most cases; hence, uncracked section properties were used in these cases. The tensile capacity was exceeded in only five walls, and in these cases, the walls were assumed cracked and the joint reinforcement will carry the tensile stresses. The cracking of sections was considered in these five walls only.

The use of joint reinforcement will be discussed later. The Licensee's response has resolved this question satisfactorily.

Question 10 Provide information on loads and load combinations applicable to masonry walls.

Response 10 The Licensee has provided the requested information on load and load combinations. A review of the plant's FSAR indicated that the loads and load combinations used are per plant FSAR and therefore satisfy the SGES criteria.

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Question 11 Describe how interstory drif t (both in-plane and out-of-plane) was accounted for.

Response 11 The Licensee's response stated that no contact existed between the top of the masonry wall and the floor above. None of the masonry walls are building structural bearing walls. Load effects due to floor differential displacements are resisted by reinforced concrete structural eieraents.

The Licensee's response is considered adequate and satisfactory.

Question 12 Provide information on construction practices and the availability of relevant quality assurance / quality control (QA/QC) records to justify the use of allowable stresses applicable to the Special Inspection Category.

Response 12 The Licensee's response supplied information on the criteria used for construction of concrete masonry walls in the plant. However, as indicated in Response No. 5, no written document was available with regara to QA/QC records; therefore, the Licensee assumed that the construction was not inspected and used the allowable stresses specified for uninspected cons truction.

The Licensee's response meets the requirements of the Uniform Building Code [9] and ACI-531-79 (10] and therefore satisfies the SGEB criteria, i

Question 13 Indicate whether the walls are stack bond or running bond. If any stack bond wall exists, provide sample calculations to obtain moment and shear stress of a typical wall.

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• i Response 13 The Licensee stated that all :nasonry walls of this plant have running bond construction, thus eliminating the concern about stack bono construction.

Question 14 Indicate how wall attachments (equipment, pipes) were considered in the-analysis.

Response 14 i

The Licensee's response indicated that there are no pipe support or equipment reactions applied to any wall. There are some light loads such as fire extir.guishers, electrical switch boxes, and conduit supports. The effects of these light loads have been considered in the analysis. The Licensee's response is judged adequate and satisfactory.

Question 15 Provide sample calculations for:

o Block pullout analysis o Missile impact.

Response 15 l

In this response, the Licensee stated that the concrete masonry walls l were not subject to missile impact.

! Regarding the block pullout analysis, the Licensee has submitted a sample calculation. A review of the calculation indicated that the pullout forces due to attached equipment have been properly accounted for. The calculated shear stress has been compared to the allowable values given in the ACI 531-79 codes. Therefore, the Licensee's response satisfies the SGEB criteria.

Question 16 r

With reference to the multiple wythes, clarify whether the collar joint strength was used in the analysis. If so, justify the values used.

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Also, on page 2 of Reference 2, the Licensee explained that, when Dur-O-Wal reinforcing has not been used, the wall strength is a multiplication of a single wythe. Explain how shear and tensi'on can be transferred along the collar joint so that the wall strength is a multiplication of single-wythe strength. Also, provide a sample calculation.

Response 16 The Licensee's response indicated that the collar joint was not used in the analysis. A sample calculation illustrating the fact that collar joint strength was not used in qualifying the multi-wythe walls has been provided

[7] . In fact, a single wythe was assumed in the analysis.

With regard to the walls without Dur-O-Wal reinforcing, the Licensee indicated that they are knockout panels which have been encapsulated within a structural steel framing.

The Licensee's response is considered adequate and meets the requirements of the SGEB criteria.

Question 17 .

Indicate if any nonlinear technique was used in the analysis. If so, provide justification for its use. If any existing test data are used to justify the technique, the applicability of the tests should be discussed for the following areas:

Nature of loads Boundary conditions Materials used Wall sizes Amount and distribution of reinforcement.

Response 17 The Licensee stated that the analysis performed was linear elastic analysis. Nonlinear analysis techniques were not used.

The Licensee's response has eliminated the concern about nonlinear analysis methods.

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Question 18 Provide the number of walls which are unreinforced. Also, provide a sample calculation illustrating how tension, shear, and displacement were obtained.

Response 18 The Licensee's response indicated that all masonry walls either have joint reinforcement (Dur-O-Wal) or are encapsulated within structural steel framing, which is a steel grating covering both faces of the wall and connected by tie i rods bolted through the walls. Regarding the use of joint reinforcement, the Licensee indicated that all but five walls were qualified relying on the mortar strength. The use of joint reinforcement is further discussed below.

The Licensee has provided a sample calculation illustrating how tension, shear, and displacement were evaluated. This calculation has been reviewed and is considered technically adequate since the analysis procedures as well as the allowable stresses were in compliance with the SGEB criteria.

Question 19 Provide detailed drawings of the modifications used. Also, provide a sample calculation to illustrate that the modified wall will be qualified under the working stress design condition.

Response 19 In response to this question, the Licensee has provided detailed drawings of the modifications. In addition, a sample calculation was provided to demonstrate that the modified wall will be qualified under the working stress design method. The modifications and sample calculation have been reviewed and found adequate; they satisfy the SGES criteria. Further discussion on the modifications will be given in Section 3.2 on the next page.

Additional Responses With regard to the use of joint reinforcement (Dur-O-Wal) to qualify the masonry walls in the plant, a list of questions was sent to the Licensee (8] .

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In its response, the Licensee indicated that Dur-O-Wal reinforcing is made of ASTM Standard A82 steel for " Cold Drawn Steel Wire for Concrete Reinforcement." However, all but five walls were qualified relying on the mortar strength. Furthermore, it was noted that if the allowable stresses for the inspected construction category were used, these five walls would be qualified without the use of Dur-O-Wal. The Licensee also indicated that efforts have been initiated to verify the existence of the Dur-O-Wal reinforcing as specified in the design specification through the use of metal detectors. The affected walls are 12-4031-Wl,1-40330-W2 and -W3, and 2-4036-W2 and -W3. NRC staff, FRC, and their consultants have conducted an exhaustive review of available information and licensees' responses to determine the technical adequacy of the use of joint reinforcement to qualify masonry walls in nuclear power plants. The Structural and Geotechnical Engineering Branch (SGEB) of the NBC is developing a position statement regarding this issue which will be available shortly.

3.2 EVALUATION OF LICENSEE'S APPROACH TO WALL MODIFICATIONS From its evaluation, the Licensee has concluded that 34 walls at the D. C. Cook Nuclear Plant Units 1 and 2 require modification. According to Reference Sc Attachment B, four types of modifications were made at the plant:

1. Beams added to the faces of walls

2. Angles added to the faces of walls

3. Grating added at knock-out areas to encapsulate block walls

4. Beams added at the ends of walls.

i All modifications were completed as of October 30, 1981.

With reference to the Response 19 (Section 3.1) , the Licensee has provided detailed drawings of the modifications. The Licensee has also provided a sample calculation demonstrating that the modified walls satisfy the SGEB criteria.

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3. REVIEW OF. CODE PROVISIONS Table 2 presents the different code design provisions concerning the role of joint reinforcement in masonry walls. As can be noted from -Table 2, these codes are rarely specific about the usefulness of joint reinforcement and its function as a structural element to carry lateral loads. The codes, however, allow the use of joint reinforcement as part of the required minimum reinforcement in reinforced masonry construction. This implies that the main structural function of joint reinforcement is to distribute the load to the mai:a vertical steel. It must be noted, however, that the codes, if they allow wire reinforcement to be used as principal reinforcing steel, specify that the working stress design (WSD) approach should be followed. The WSD approach assumes linear elastic material properties and limits the allowable steel stress to 30,000 psi.

The new edition (1982) of the Uniform Building Code (UBC) allows the use

, of joint reinforcement as principal horizontal steel to carry design stresses

[13]. This is, however, lim.' ed to reinforced masonry walls designed using the WSD method.

The design provisions of most codes apply to masonry buildings under static loads. ATC-3 [3] is the only code that specifies die structural use of ,

joint reinforcement under earthquake loads in seismic areas. It does permit the use of joint reinforcement to resist tensile stresses for seismic Category A and B structures, but states that it cannot be used as the principal reinforcement for Categories C and D structures, except as part of the minimum reinforcing requirements.

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4. DESIGN OF MASONRY WALLS WITH JOINT REINFORCEMENT I .

North American codes for reinforced masonry design assign allowable flexural compressive stresses for masonry and tensile stresses for reinforcing steel. Table 3 presents calculated allowable moments /f t of typical 8-in hollow block walls which span horizontally based on the working stress design. It is assumed that the wall is cracked and that steel carries all the tension. The allowable moment (M g) the unreinforced wall carries hori=ontally is calculated based on an allowable flexural stress of 1.0'V3['

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,; 2 Table 2. Code Design Provisions for Joint Reinforcement Code -

Design Provisions ACI (1] Section 6.7

" Horizontal joint reinforcement mag be

' used in the wall to increase the tensile resistance and as a means to resist design tensile stresses."

Section 8.2 "The function of joint reinforcement is j to prevent the formation of excessively j large, unacceptable shrinkage cracks in

, masonry walls. "

UBC [12] Section 2418 "The minimum diameter of reinforcement shall be 3/8 inch except that joint reinforcement may be considered as part of the required minimum reinforcement."

NOMA [15] Section 3.10 " Approved wire reinforcement, placed in horizontal mortar joint, may be used as part of the required reinforcement."

ATC [3] Section 12.5.1 " JOINT REINFOICEMENT: Longitudinal masonry joint reinforcement may be used in reinforced grouted masonry and reinforced hollow unit masonry only to fulfill minimum reinforcement ratios but shall not be considered in the determination of the strength of the me mber . "

CSA [6] Section 4.6.8.1 " Wire reinforcement in the mortar joints i may be considered as required horizontal l reinforcement."

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Note:

No provisions are given in BS 5628 [4] or TMS (16] concerning the use of joint reinforcement.

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• Table 3. Allowable Moments l Joint Calculated Allowable MAR

• Reinforcement Moment, MAR, lb-in/f t [10] Mgg i

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9 gage 8 in o.c. 4880 1.42

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16 in o.c. 2440 0.71 l

8 gage 8 in o.c. 5820 1.69 16 in o.c. 2910 0.85 3/16" 8 in o.c. 7430 2.16 16 in o.c. 3720 1.08 f'm = 2000 psi, fm = 0.33 f'ar fs = 3 0 00 0 T.si, type S-morta r, 7

• ratio of calculated moment of reinforced wall to unreinforced wall (M3g =

3436 lb-in/f t) .

The results presented in Table 3 show that the allowable moments for i

masonry walls spannina horizontally depend primarily on the steel ratio. It is interesting to note that joint reinforcement at lower percentages does not increase the wall resistance.

The contribution of joint reinforcement in the ultimate (failure) lateral load resistance of masonry walls was calculated by Cajdert [5] . He assumed a linear bending strain with a triangular stress distribution in the compression zone. The ultimate strength is assumed to be reached when, af ter yielding of the tensile reinforcement, the ultimate masonry strength, f',, is reached.

It must be r.oted that the joint rcinforcement is high tensile steel with a f yield stress as high as 100,000 psi. No published data are available on its stress-strain behavior which is needed in the ultimate load analysis.

Cajdert's (5) approach of ultimate stress design necessitates precluding any l

bond failure to develop yielding of the joint reinforcement.

S. COICLUSIONS AND RECOMMENDATIONS The structural performance of joint reinforcement is not well established.

The qualification of masonry' walls in nuclear power plants which takes into j account tensile stength due to joint reinforcement is questionable. This is based on the following arguments:

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1. The availabl'e test data are- scarce. Conflicting values have been obtained concerning the contribution of joint reinforcement. Also, the statistical significance of so few samples of such a variable material'is questionable.

2. All the tests were performed under static loading which cannot be extrapolated to predict the performance under earthquake loads, which are dynamic and cyclic, fully reversed in nature. Tne only test data for cyclic static loading showed a dramatic decrease in strength of 33% in half a cycle. This indicates the possibility of severe strength deterioration under multiple reversed cyclic dyna =ic loading.

3. Masonry codes are not specific about the usefulness of joint reinforcement. Its use is allowed to satisfy the minimum steel requirements for reinforced masonry. If it is to be used to resist tensile stresses, the WSD method should be employed with an allowable steel stress limited to 30,000 psi. This approach limits the contribution of joint reinforcement in increasing the allowable moment over that of unreinforced walls with running bond. It must be noted that codes allow the use of joint reinforcement as a structural steel only in reinforced walls which satisfy the minimum steel requirements in both vertical and horizontal directicas. This may not be the case for the masonry walls in nuclear power plants.

4. The only code [3] that addresses the use of joint reinforcement in seismic areas does not allow its use as principal steel for Categories C and D s tructures. Safety-related masonry walls in nuclear power plants would fit into these categories.

5. For hollow block walls with joint reinforcement, cracking extends to the compression face shell causing a dramatic reduction in wall stiffness and consequently excessive deflection, particularly under cyclic loading.

A serviceability limit state should be applied to assure proper performance of wall attachments (pipe s) . - This limit state =ay restrict the performance of joint reinforcement to the linearly elastic stage.

6. Unreinforced walls in nuclear power plants that are joint reinforced to span horizontally should have base boundary conditions which are free to allow both translation and rotation in the out-of-plane direction. This boundary condition, if it exists, forces the wall to transfer its self weight by beam action to the vertical support.

Therefore, the wall is under in-plane and out-of-plane forces. The effect of possible interaction on the wall performance, particularly under cyclic dynamic loads, is not known.

In conclusion, the state-of-the art does not give enough insight to understand the performance of joint reinforcement under seismic loads.

Therefore, it is the FRC consultants' opinion that nja credit should be given 4 b Franklin,n.esearch a cm.aa . . ma wi,u. Center R

to joint reinforcement to resist tensile stresses due to earthquake loads. A confirmatory test program is therefore recommended to provide data about the structural performance of joint reinforcement in block masonry walls under cyclic dynamic loading.

6. REFERENCES

1. American Concrete' Institute, " Building Code Requirements for Concrete Masonry Structures," ACI Standard 531-79, Detroit, Michigan

2. Anderson, D. L. , Nathan, N. D. , Cherry, S. , and Crajer, R. B. ," Seismic Design of Reinforced Concrete Masonry Walls," Proceedinos of the Second Canadian Masonry Svmoosium, Ottawa, Canada, June 1980

3. Applied Technology Council, " Tentative Provisions for a Development of Seismic Regulations for Buildings," ATC 3-06 (NSF Publication 78-8, NBS Special Publication 510), U.S. Government Printing Office, June 1978

4. British Standard Institution, "The Structural Use of Masonry," BS 5628:

Part 2: Reinforced and Prestressed Masonry, London, 1981

5. Cajdert, A., " Laterally Loaded Masonry Walls," Ph.D. Thesis, Chalmers University of Technology, Goteberg, Sweden,1980

6. Canadian Standard Association, " Masonry Design and Construction for Buildings," Standard S304-M78, Rexdale, Ontario, Canada, 1978

7. Cox, F. W. and Ennenga, J. L., " Transverse Strength of Concrete Block Walls," Proceedings of American Concrete Institute, Vol. 57, 1961

8. Churchward, G. and Mattison, E. N., "Some Tests on the Bending Strength of Concrete Masonry in Running Bond," Division of Building Research, Melbourne, Australia,1969

9. Dickey, W. L., " Joint Reinforcement and Masonry," Proceedings of the Second North American Conference, College Park, Maryland, August 1982

10. DUR-O-WAL Technical Bulletin No. 74-6, "DUR-O-WAL Masonry Reinforcement in High-Rise Bearing Wall Buildings," January 1974 l

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11. Hedstrom, R.O. , " Load Tests of Patterned Concrete Masonry Walls,"

Proceedinos of American Concrete Institute, Vol. 57, 1961 l

12. International Conference of Building Officials, " Masonry Codes and Specifications," 1979 UBC, Chapter 14, Whittier, California,1979 SJ Franklin h w m i-Research Center

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13. International Conference of Building Officials, Research Report No. 2292, January 1982

14. National Concrete Masonry Association, "The Structural Role of Joint Reinforcement in Concrete Masonry," TEK-99,1978

15. National Concrete Masonry Association, " Specification for the Design,and Construction of Ihad-Bearing Concrete Masonry," herndon, Virginia,1979

16. The Masonry Society, " Standard Building Code Requirements for Masonry Cons truction," Boulder, Colorado, August 1981 l

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