ML20080H068
| ML20080H068 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 09/16/1983 |
| From: | Con V, Le A FRANKLIN INSTITUTE |
| To: | Nilesh Chokshi NRC |
| Shared Package | |
| ML20080E255 | List: |
| References | |
| CON-NRC-03-81-130, CON-NRC-3-81-130 TAC-42925, TER-C5506-242, NUDOCS 8309200506 | |
| Download: ML20080H068 (31) | |
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TECHNICAL EVALUATION REPORT MASONRY WALL DESIGN PUBLIC SERVICE COMPANY OF COLORADO FORT ST. VRAIN NUCLEAR PLANT NRC DOCKET NO. 50-267 FRC PROJECT C5506 NRC TAC NO. 42925 FRC ASSIGNMENT 6 NRC CONTR ACT NO. NRC-03-81-130 FRC TASK 242 Prepared by
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Franklin Resea> h Center Author: 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. C. Chokshi September 16, 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 represents that its use by such third party would not infringe privately owned rights.
Prepared by: Reviewed by: Approved by:
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Priricipal Author: Group Leader Department Director (Accing)
Date: O./6-83 Date: Cf - 14 , ( ( Date: 7 /d/8 XA Copy Has Been Sent is PDR A
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TER-C550 6-24 2 CONTENTS Section Title Page 1 INTRODUCTION . . . . . . . . . . . . . 1 1.1 Purpose of Review . . . . . . . . . . . 1 1.2 Generic Issue Background . . . . . . . . . 1 1.3 Plant-Specific Background . . . . . . . . . 1 2 REVIEW CRITERIA. . . . . . . . . . . . . 4 3 TECHNICAL EVALUATION . . . . . . . . . . . S 3.1 Evaluation of Licensee's Criteria . . . . . . . 5 3.2 Evaluation of Licensee's Approach to Wall Modifications . . . . . . . . . . . . 14 4 CONCLUSIONS. . . . . . . . . . . . . . 16 5 REFERENCES . . . . . . . . . . . . . . 17 APPENDIX A - SGEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRA!CH [SGEB] OF THE NBC)
APPENDIX B - SKETCH OF WALL MODIFICATIONS g3 iii
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3 TER-C5506-242 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 Nuclear Regulatory Commission (NRO) masonry wall criteria. In additic.., ir the Licensee plans repair work on masonry walls, the planned methods, procedures, and repair schedules are reviewed for acceptability.
1.2 GENERIC ISSUE BACKGROUND In the course of conducting inspections at the Trojan Nuclear Plant, Portland General Electric Company determined that some concrete masonry walls did not have adequate structural strength. Further investigation indicated that the problem resulted from errors in engineering judgment, a lack of established procedures and procedural details, and inadequate design criteria. Because of the implication of similar deficiencies at other operating plants, the NBC issued IE Bulletin 80-11 on May 8,1980.
IE Bulletin 80-11 required licensees to identify plant masonry walls and their intended functions. Licensees were also required to present reevaluation I
criteria for the masonry walls with the analyses to justify those criteria.
If modifications were proposed, licensees were to state the methods and schedules for the modifications, j 1.3 PLANT-SPECIFIC BACKGROUND In response to IE Bulletin 80-11, Public Service Company of Colorado provided the NBC with letters dated July 7,1980 [2] and October 28, 1980 [3]
describing the status of masonry walls at the Fort St. Vrain Nuclear Plant.
Also, the Licensee Event Report was sent to the NRC on March 9,1983 [4]
describing the status of four masonry walls that required modifications due to discrepancies in their construction, in which joint reinforcement was specified in the design but was not found in these walls. The information in these letters was reviewed, and requests for additional information were sent I
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TER-C5506-242 to the Licensee on July 21, 1982 [5] and November 19, 1982 [6] . The Licensee responded to these requests on August 24, 1982 [7] and January 11, 1983 (8).
The Licensee reviewed 98 walls and identified 65 walls as safety-related according to IE Bulletin 80-11. These walls are located in the reactor and turbine buildings.
All walls analyzed in the turbine building are hollow, single-wy the ,
non-load-bearing walls serving one of two main functions:
- 1. separation of major equipment components
- 2. enclosures for rooms such as the maintenance shop.
All walls analyzed in the reactor building are solid, single-wythe, non-load-bearing walls serving one of three main functions:
- 1. separation of major equipment components
- 2. enclosures for pipe chases
- 3. radiological shielding similar to that in the liquid and gas waste facility.
The wall types and materials for the Fort St. Vrain Nuclear Plant are given below:
Wall Tyoes:
Total number of walls 98 Safety-related walls 65 Walls requiring modifications 16 Construction Materials:
Masonry - ASTM 90, Type I, Grade U-1, minimum compressive strength (f'm) of 1350 psi Mortar - Minimum compressive strength (M o) of 1200 psi with the following constituents Cemen t:
Portland cement: ASTM C150, Type I or II Masonry cement: ASTM C91, Type II A
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TER-C550 6-24 2 Lime:
Quick lime: ASTM C5 Hydrated lime: ASTM C207, Type S Masonry Sand: ASTM C144, natural sand only Mixing Water: ASTM 270 The walls are installed with "Dur-O-Wal" wire but have no vertical reinforcement. The majority of attachments are items such as electrical conduit and 2-in or less Class II piping supports. No Class I piping is attached to masonry block walls.
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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 NIC (attached as Appendix A to this report) , the Uniform Building Code [9],
and ACI 531-79 [10].
In general, the ma'arials, testing, analysis, design, construction, and inspection of safety-related concrete masonry walls 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 Final Safety Analysis Report (FSAR) for the plant. Allowable stresses are specified in Reference 10, 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, 3] and subsequent responses (7, 8] to the requests for additional information [5, 6]. The Licensee's criteria [3] were evaluated with regard to design and analysis methods, loads and load combinations, allowable stresses, construction specifications, materials, and relevant test data. The Licensee's responses to the requests for additional information were also reviewed.
3.1 EVALUATION OF LICENSEE' S CRITERIA The Licensee reevaluated the masonry walls using the following criteria
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o The design allowables are based on ACI 531-79 (10] .
o The working stress design method is used in the analysis.
o The load combinations used in the analysis, which include dead load, live load, and seismic load, are consistent with the FSAR.
o The walls are modeled as horizontal span or vertical span beams. The end conditions are considered as being simply supported for walls that span from floor to floor or from column to column, or as cantilevered fixed support for walls that do not span from floor to ceiling.
o The following criteria are used to compute the response of masonry walls to seismic forces:
5% damping is used for all walls under design basis earthquake (DBE) .
- The envelope of floor response spectra is used.
- Seismic moment and shear are multiplied by a factor of 1.05 to account for the contribution of higher mode effects of wall vibration.
- The loads of the equipment and piping attached to the wall are considered in the analysis, o No thermal effects due to pipe growth are considered since there are no thermal lines attached to Class I masonry block walls.
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TER-C550 6-242 o Differential story displacements are small enough that the strains that would be produced in the wall would result in very small stresses, o Initially, joint reinforcement (Dur-O-Wal) was used to qualify 22 masonry walls without vertical reinforcement. However, four walls were found with joint reinforcement discrepancies; therefore , they will be modified. Also, one wall can be qualified without relying on joint reinforcement. Therefore, only the 17 remaining walls were qualified by using joint reinforcement.
Except for those areas identified in Section 4, the Licensee's criteria are found to be adequate and in compliance with the SGEB criteria. Following is the review of the Licensee's responses (7, 8] to the requests for additional information [5, 6].
Request 1 Indicate whether the walls are stack bonded or running bonded. If any stack bond wall exists, provide sample calculations to obtain moment and shear stress of a typical wall.
Response 1 The Licensee confirmed that all masonry block walls at Fort St. Vrain plant are running bond. No stack bond wall exists at the plant. The Licensee's response has resolved the concern of stack bond construction at the Fort St. Vrain plant.
Request 2
! Describe the s'sumptions, modeling techniques, and procedures used in the analysis.
j Response 2 The Licensee provided the assumptions used in the analysis, s te p-by-s tep analysis procedures, and the allowable stresses for the walls. Tnis 1
information is summarized below:
o Determine the reactions, shear, and moments for the wall due to attachment and its own dead weight.
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l TER-C5506-242 o Calculate the natural frequency of the wall using formulas for simply supported and cantilever beams, o Calculate the seismic moment and shear by multiplying the g factor (selected from enveloped floor response sepctra) to the maximum shear and moment obtained from attachment and dead weight analysis.
o Calculate the wall stresses using combined axial and bending stress formulas.
o The following allowable stresses were used in the analysis of the masonry block walls (ACI 531-72):
Tension normal to bed joints 21.3 psi Tension parallel to bed joints 42.6 psi Shear . s tress 30.6 psi The Licensee's response indicated that its approach is adequate and satisfies dae SGEB criteria.
Request 3 Indicate how frequency variations due to uncertainties in mass, i materials, and other parameters were considered.
Response 3 The Licensee indicated that frequency variations due to uncertainties in mass, materials, and wall thickness were considered but were found not to
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affect the results of the analysis.
The Licensee's response is adequate and meets the intent of the SGEB criteria.
Request 4 Using sample calculations, show how it was determined that seismic differential floor displacements are negligible (3] .
Response 4-The Licensee indicated d2at the maximum horizontal seismic drif t for walls spanning from floor to ceiling is 0.007 f t. For confined walls at the U$d Franklin Research Center
TER-C5506-242 Fort St. Vrain plant, the permissible lateral strain is y = 0.001. The minimum height of the wall was derived from those two quantities and was found to be 7 ft. All walls at the Fort St. Vrain plant are greater than 7 f t in height; therefore , the Licensee concluded that seismic differential floor displacement is not a concern at the Fort St. Vrain plant.
The Licensee's response is satisfactory and meets the intent of the SGEB criteria.
Request 5 Regulatory Guide 1.61 allows 4% damping for an operating basis earthquake and 7% damping for a safe shutdown earthquake. Provide damping values used in the analysis and justify them if they are higher than those allowed in Regulatory Guide 1.61.
Response 5 The Licensee indicated that 5% damping was used for the DBE event. The Licensee has not provided the damping factor for OBE. However, in a telephone conference between the NBC staff and a Fort St. Vrain representative on August 29,_1983, the Licensee indicated that DBE is the governing case and that DBE response spectra, in general, are twice as great as those for OBE. The Licensee indicated in Response 10 that the increase factor for DBE is 1.33,
, which is in compliance with the SGEB criteria. Moreover, the Licensee used 5%
damping for DBE, which is more conservative than the damping ratio of 7%
i specified in Regulatory Guide 1.61. Therefore, the Licensee's response is considered adequate and satisfies the SGEB criteria.
Request 6 Indicate the boundary conditions used for analyzing masonry walls and provide justification.
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Response 6 The Licensee's response indicated that a pinned, fixed, or free-end boundary condition was used in the analysis. A fixed boundary condition was i
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TER-C550 6-242 assumed for walls embedded into concrete floors; a pinned boundary condition was used for walls framing into structural steel or concrete; and a cantilever wall was assumed when the top of the wall is free. Sample calculation for Wall 16 indicated that calculated shear stress at the boundary is 4.5 psi, which is much less than the allowable shear stress of 23 psi. For walls embedded into concrete floors, it is judged that this embedment should be able to prevent rotation. Therefore, the boundary conditions used by the Licensee are judged to be reasonably adequate.
Request 7 Specify material types used for masonry and mortar, and provide their compressive strengths f'm and m e, respectively.
Response 7 The Licensee has provided appropriate information on the type of masonry and mortar used for the plant (see Section 1.3) . Also, the Licensee has provided the compressive strength for masonry as 1350 psig (f',) and as 1200 psi for mortar.
The Licensee's response is satisf actory and in compliance with the SGEB 1 criteria.
Request 8 l
Provide values of allowable shear stresses in flexural members and shear walls for cases in which there is no shear reinforcement'and for cases in l which reinforcement takes the entire shear.
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l Response 8 l The Licensee confirmed that the masonry block walls at the Fort St. Vrain plant are unreinforced and that the allowable shear stress used for the DBE event is 30.6 psi. This allowable is considered reasonable since the ACI-531-79Codeallowedavalueof0.9,[f',,whichisequivalentto33 psi with the compressive strength f' = 1350 psi.
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TER-C5506-242 The Licensee's response is satisfactory and in compliance with the SGEB criteria.
Request 9 Provide information on construction practices and availablity of relevant quality assurance / quality control records to justify the use of allowable stresses applicable to the Special Inspection Category.
Item 1 in Reference 7 Since no quality assurance records are available the Licensee is requested to confirm that Dur-O-Wal exists in the walls as specified in the design. Also provide available data to justify the yield strength of Dur-O-Wal used in the analysis. In addition, provide verification to assure proper anchorage of Dur-O-Wal at the boundary and proper bonding between Dur-O-Wal and mortar. Further, justify the use of Dur-O-Wal as a reinforcing element considering the fact that this is not normally used in such capacity. Include applicable test data in your justification.
Responses to Request 9 and Item 1 in Reference 7 The Licensee indicated that all of the 22 walls that were qualified relying on the strength of Dur-O-Wal were investigated to verify that Dur-O-Wal does exist. It was verified that Dur-o-Wal exists in 17 of the walls by means of a metal detector and by removing mortar in various locations to check the Dur-O-Wal size and bond.
Five walls were noted to have discrepancies between the installed Dur-O-Wal and what was originally specified (walla 49, 51, 95, 100, and 101).
Reanalysis of wall 51, which has a very short span length, showed that there is adequate strength in the masonry to resist the various loads and that Dur-O-Wal would not be required to maintain wall integrity. The modifications (bar straps will be used, according to the Licensee Event Report (4]) for the remaining four walls (49, 95,100, and 101) would be completed by March 15, 1983.
The Licensee indicated that the maximum stress of 40 psi was used in the analysis of Dur-O-Wal steel compared to the minimum yield strength of 64 psi for normal cold-drawn steel wire used for Dur-O-Wal.
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TER-C550 6-242 The Licensee indicated that no credit was taken for the Dur-O-Wal at the boundary support. The shear strength of mortar is sufficient in resisting the seismic loads.
However, NRC staff, FRC, and their consultants have conducted a review of available information and licensees' responses to determine the technical adequacy of the use of joint reinforcement to qualify masonry walls in nuclear plants. The Structural and Geotechnical Engineering Branch of the NRC has developed a position statement regarding this issue, and it will be addressed in the NRC staff's Safety Evaluation Report.
Request 10 Provide any increase factors that may have been used for allowable stresses under abnormal loading conditions. If they are higher than those factors listed in the SGEB criteria, provide justification. The SGEB factors are listed below by type of stress.
Axial of flexural compression 2.5 Bearing 2.5 Reinforcement 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 10 The Licensee indicated that all allowable concrete masonry stresses were increased by 33% for the DBE event. This increase factor is satisfactory and in compliance with the SGEB criteria.
Request 11 Provide information on loads and load combinations applicable to masonry walls.
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l TER-C5506-242 Response 11 The Licensee provided information on loads and load combinations, which
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are consistent with the FSAR. Loads considered are dead load, live load, and design basis earthquake load. The Licensee's response is considered adequate and meets the intent of the SGEB criteria.
Request 12 Provide sample calculations for missile impact (if applicable) .
Response 12 The Licensee clarified that masonry walls at the Fort St. Vrain plant were neither designed nor required to withstand missile impact. The Licensee response is satisfactory and in compliance with the SGEB criteria.
Request 13 Indicate if any nonlinear technique was used in the analysis. If so, provide justification for its use. If the Licensee intends to use any existing test data to justify this technique, the Licensee is requested
'to discuss the applicability of these tests to the masonry walls at the plant to the following areas:
o Nature of the loads o Boundary conditions o Materials used o Wall size -
o Amount and distribution of reinforcement.
Response 13 f
The Licensee confirmed that no nonlinear analysis technique was used in the analysis. The Licensee's response is satisfactory and in compliance with the SGEB criteria.
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Request 14 Provide details of wall modifications with drawings. Also, provide a sample calculation to illustrate that the walls can be qualified under working stress design conditions af ter modification.
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Response 14 1
The Licensee has used bar straps spanning vertically to modify 16 walls.
i The' bar straps were attached to the floor by clip angles and anchors. The bar straps are 2-in wide and 1/4-in thick at 4-f t spacing (see sketch in Appendix 1
B). The Licensee provided sample calculations for wall modifications using bar straps. The calculations for wall 16 showed that the calculated moment of 4721 lb and shear stress of 4.5 psi are less than the isoment capacity of the bar straps of 6015 f t-lb and the allowable shear of 23 psi, respectively.
The Licensee's response is considered adequate and in compliance with the SGES criteria.
Item 2 of Reference 7 Provide data to justify the strength of the bar straps used in wall modifications.
i Response to Item 2 of Reference 7 The Licensee indicated that the bar straps used in the wall modifications are ASTM A36 steel, which is a low-strength steel, and any steel used would l- have a minia'am tensile strength of ASTM A36 steel.
~ The Licensee's response is adequate and in compliance with the SGEB criteria.
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. . ve,rify whether load combinations used are in compliance with the plant
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l l Response to Item 3 of Reference 7 The Licensee stated that the FSAR does not address load combinations on masonry block walls; however, concrete load combinations were used in the analysis of masonry block walls. The FSAR load combinations include dead
, load,-live load, earthquake, wind, and tornado loads. However, wind and e' ,
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tornado loads are not applicable to masonry walls at Fort St. Vrain Nuclear Plant.
The Licensee's response is adequate and satisfies the SGEB criteria.
Item 4 of Reference 7 Indicate the number of walls which were qualified by relying on the strength of Dur-O-Wal and that of bar straps. Also, provide the status of wall modifications.
Response to Item 4 of Reference 7 The Licensee indicated that originally 22 walls were qualified relying on the strength of Dur-O-Wa1. However, four walls were found to be missing joint reinforcement; therefore, they will be modified using bar straps. Also, one wall was found that can be modified without relying on joint reinforcement.
Therefore, only the 17 remaining walls were qualified using joint reinforce-ment. Sixteen walls were qualified by use of bar straps attached to the walls.
All wall modifications for the 16 walls requiring bar straps were completed in 1982. The modifications to the four walls which had Dur-O-Wal discrepancies were to be completed by March 15, 1983.
The Licensee's response is satisfactory.
3.2 EVALUATION OF LICENSEE'S APPROACH TO WALL MODIFICATION
.The Licensee identified 16 walls to be modified as stated in response to Item 4 of Reference 8. Bar straps were used on both sides of the wall and attached to it by thrubolts. The bar straps provided additional flexural strength to the wall. Also, the Licensee Event Report (4) indicated that those four walls in which joint reinforcement was missing will be modified using bar straps.
The Licensee's approach to wall modification is judged to be adequate, and the modified walls satisfy the SGES criteria with regard to the allowables.
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The Licensee stated that all modifications with regard to the 16 masonry block walls requiring bar straps were completed. The modifications to the four walls which had Dur-O-Wal discrepancies were to be completed by March 15, 1983.
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, 4. CONCLUSIONS A detailed study was performed to provide a technical evaluation of the masonry walls at Fort St. Vrain Nuclear Plant. Review of the Licensee's criteria and additional information provided by the Licensee led to the conclusions given below.
The criteria used for reevaluation of the masonry walls, along with the additional information provided by the Licensee, indicated that the Licensee's criteria are in complaince with the SGEB criteria (Appendix A) except for the following cases o The Licensee only considered the seismic analysis for DBE. However, in the telephone conference between the NBC and Fort St. Vrain staff, the Licensee indicated that DBE is the governing case and that DBE is twice as great as OBE. Therefore, the Licensee's approach in considering only the DEE governing case for the masonry wall seismic analysis is adequate.
o Joint reinforcement (Dur-O-Wal) has been used to qualify 17 unreinforced masonry walls at Fort St. Vrain Nuclear Plant. This issue will be addressed in the NBC staff position which will be addressed in the Safety Evaluation Report.
The Licensee's approa. h to wall modifications has been reviewed and is judged to be adequate and in compliance with the SGEB criteria.
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- 5. REFERENCES
- 1. Masonry Wall Design NBC, 08-May-81 IE Bulletin 80-11
- 2. F. E. Swart Letter to K. V. Seyfrit
Subject:
Masonry Block Walls, 60-Day Response to IE Bulletin 80-11 Public Service Company of Colorado, 7-Jul-80
- 3. F. E. Swart Letter to K. V. Seyfrit
Subject:
Masonry Block Walls (180-Day Response to IE Bulletin 80-11)
Public Service Company of Colorado, 28-Oct-80
- 4. D. Warenbourg Letter to J. T. Collins, NRC
Subject:
Fort St. Vrain Unit 1 - Reportable Occurrence Report No.
50-267/83-009 March 9, 1983
- 5. R. A. Clark (NRC)
Subject:
Fort St. Vrain - Masonry Wall Design, IE Bulletin 80-11, Request for Additional Information July 21, 1982
- 6. R. A. Clark (NRC)
Subject:
Fort St. Vrain - Masonry Wall Design, IE Bulletin 80-11, Request for Additional Information Novembe 9, 1982
- 7. O. R. Lee Letter to R. A. Clark, NBC
Subject:
IE Bulletin 80-11, Masonry Walls Public Service Company of Colorado August 24, 1982
- 8. H. L. Brey Letter to R. A. Clark, NBC
Subject:
Masonry Block Walls - Responses to Request for Additional Information Public Service Company of Colorado January 11, 1983
- 9. Uniform Building Code International Conference of Building Officials, 1979 bNOU Franklin Research Center
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- 10. Building Code Requirements for Concrete Msonry Structures Detroit: Ainerican Concrete Institutie, 1979 ACI 531-79 and ACI 531-R-79 M
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APPENDIX A SGEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BPA!CH
[SGEB] OF THE NRC)
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COhTENTS Section Title Page 1 GENERAL RMUIREMENTS . . . . . . . . . . . A-1 2 LOADS AND LOAD COMBINATIONS. . . . . . . . . . A-1
- a. Service Load Combinations . . . . . . . . . A-1
- b. Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmental Conditions . . . . . . . . . . . . . A-2 3 ALLOWABLE STRESSES . . . . . . . . . . . . A-2 4 DESIGN AND ANALYSIS CONSIDERATIONS . . . . . . . . A-3 5 REFERENCES . . . . . . . . . . . . . . A-4 iii O
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- 1. General Recuirements The materials, testing, analysis, design, construction, and inspection related to the design and construction of safety-related concrete masonry walls should conform to the applicable requirements contained in Uniform Building Code - 1979, unless specified otherwise, by the provisions in this criteria.
The use of other standards or ccdes, such as ACI-531, ATC-3, or NCMA, is also acceptable. However, when the provisions of these codes are less conservative than the corresponding provisions of the criteria, their use should be justified on a case-by-case basis.
In new construction, no unreinforced masonry walls will be permitted. For operating plants, existing unreinforced walls will be evaluated by the provisions of these criteria. Plants which are applying for an operating license and which have already built unreinforced masonry walls will be evaluated on a case-by-case basis.
- 2. Loads and Load Combinations The loads and load combinations shall include consideration of normal loads, severe environmental loads, extreme environmental loads, and abnormal loads. Specifically, for operating plants, the load combinations l provided in the plant's FSAR shall govern. For operating license applications, the following load combinations shall apply (for definition of load terms, see SRP Section 3.8.4II-3) .
(a) Service Load Conditions (1) D+L (2) D+L+E (3) D+L+W l If thermal stresses due to oT and Ro are present, they should be included in the above combinations as follows:
(la) D + L + To + Ro (2a) D+L+To+Ro+E (3a) D+L+To+Ro+W Check load combination for controlling condition for maximum 'L' and for no 'L'.
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TER-C5506-24 2 (b) Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmental Conditions (4 ) D + L + To + Ro + E (5) D + L + To+Ro+Wt (6) D + L + Ta+Ra + 1.5 Pa (7) D + L + Ta + Ra + 1.25 Pa + 1.0 (Yr + Yj + Ym) + 1.25 E (8) D+L+Ta+Ra + 1. 0 Pa + 1. 0 (Yr + Yj + Y )m + 1. 0 E '
In combinations (6), . (7) , and (8) the maximum values of Pa' Ta '
Rat Yja Yr , and Ym, including an appropriate dynamic load factor, should be used unless a time-history analysis is performed to justify otherwise. Combinations (5), (7) , and (8) and the corresponding structural acceptance criteria should be satisfied first without the tornado missile load in (5) and without Yr, Yj, and Y m in (7) and (8). When considering these loads, local section strength capacities may be exceeded under these concentrated loads, provided there will be no loss of function of any safety-related system.
Both cases of L having its full value or being completely absent should be checked.
- 3. Allowable Stresses Allowable stresses provided in ACI-531-79, as supplemented by the following modifications / exceptions, shall apply.
(a) When wind or seismic loads (OBE) are considered in the loading combinations, no increase in the allowable stresses is permitted.
(b) Use of allowable stresses corresponding to special inspection category shall be substantiated by demonstration of compliance with the inspection requirements of the SEB criteria.
(c) When tension perpendicular to bed joints is used in qualifying the unreinforced masonry walls, the allowable value will be justified by test program or other means pertinent to the plant ano loading conditions. For reinforced masonry walls, all the tensile stresses will be resisted by reinforcement.
(d) For load conditions which represent extreme environmental, abnormal, abnormal / severe environmental, and abnormal / extreme environmental
- conditions, the allowable working stress may be multiplied by the factors shown in the following table
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TER-C5506-242 Type of Stress Factor Axial or Flexural Compression 2.5 Bearing 2.5 Reinforcement 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 for reinforced masonry 0 for unreinforced masonry 2 1,3 Notes (1) When anchor bolts are used, design should prevent facial spalling of masonry unit.
(2) See 3 (c) .
- 4. Design and Analysis Considerations (a) The analysis should follow established principles of engineering mechanics and take into account sound engineering practices.
(b) Assumptions and modeling techniques used shall give proper considerations to boundary conditions, cracking of sections, if any, and the dynamic behavior of masonry walls.
(c) Damping values to be used for cynamic analysis shall be those for reinforced concrete given in Regulatory Guide 1.61.
(d) In general, for operating plants, the seismic analysis and Category I structural requirements of FSAR shall apply. For other plants, corresponding SRP requirements shall apply. The seismic analysis shall account for the variations and uncertainties in mass, materials, and other pertinent parameters used.
(e) The analysis should consider both in-plane and out-of-plane loads.
(f) Interstory drift effects should be considered.
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TER-C550 6-24 2 (g) In new construction, grout in concrete masonry walls, whenever used, l shall be compacted by vibration.
(h) For masonry shear walls, the minimum reinforcement requirements of ACI-531 shall apply.
(i) Special constructions (e.g. , multiwythe, composite) or other items not covered by the code shall be reviewed on a case-by-case basis for their acceptance.
(j) Licensees or applicants shall submit QA/QC informaticn, if available, for staff's review.
In the event QA/QC information is not available, a field survey and a test program reviewed and approved by the staff shall be implemented to ascertain the conformance of masonry construction to design drawings and specifications (e.g., rebar and grouting).
(k) For masonry walls requiring protection from spalling and scabbing due to accident pipe reaction (Y r ), jet impingement (Y3 ) , and missile impact (Y m), the requirements similar to those of SRP 3.5.3 shall apply. However, actual review will be conducted on a case-by-case basis.
- 5. References (a) Uniform Building Code - 1979 Edition.
(b) Building Code Requirements for Concrete Masonry Structures ACI-531-79 and Commentary ACI-531R-79.
(c) Tentative Provisions for the Development of Seismic Regulations for Buildings - Applied Technology Council ATC 3-06.
(d) Specification for the Design and Construction of Load-Bearing Concrete Masonry - NCMA August, 1979.
(e) Trojan Nuclear Plant Concrete Masonry Design Criteria Safety Evaluation Report Supplement - November,1980.
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APPENDIX B SKETCH OF WALL MODIFICATIONS A4
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i Attachment 2 SGEB Staff Position on the Use of Joint Reinforcing in Qualifying Unreinforced Masonry Walls
- Introduction The function of joint reinforcement in masonry walls is to prevent the formation of unacceptable shrinkage. cracks. The structural significance (i.e., to provide resistance to tensile stresses) of joint reinforcement
.....in,, masonry,wal_1.s is not , wel.1 established. - This is particularly true for unreinforced hollow block masonry walls subject to cyclic dynamic loading. However, some licensees have proposed to use joint reinforcement as a structural element to qualify unreinforced masonry walls in their plants.
The staff and their consultants have reviewed the technical justifications provided by scme licensees for using the joint reinforcing (such as 'Dur Wal') as a structural element in qualifying masonry walls which are unreinforced or do not meet the minimum reinforcement requirements of the Uniform Building Code. The staff has further reviewed the ' test results available in the literature, codes, and other pertinent information. Based on these reviews, the staff has formulated the following position on-the use of joint reinforcing as a structural reinforcing element in unreinforced masonry walls. The
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staff's technical. basis for this position is discussed in the attached report.
2-Position The use of joint reinforcing as a structural element (to evaluate the capacity of the wall in resisting applied laods) for qualifying masonry walls not meeting the minimum reinforcement requirements with respect to steel ratios, spacing, etc., of the Uniform Building Code-1979 edition ,
is not acceptable *. Therefore, the licensee shall fix the walls currently qualified by the use of joint re'inforcing as a structural element such that they meet the staff's acceptance criteria for unreinforced walls (Appendix A of TER, Attachment 1).
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- As noted in the attached report, the use of high allowables in joint reinforcernent, say beyond 30,000 psi, even in the case of reinforced walls is questionable and not acceptable. However, this position only addresses the use of join-t reinforcing in unreinforced walls. ,
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