ML19344A408
| ML19344A408 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 07/31/1980 |
| From: | Colville J MARYLAND, UNIV. OF, COLLEGE PARK, MD |
| To: | |
| Shared Package | |
| ML19344A406 | List: |
| References | |
| TAC-12369, NUDOCS 8008200206 | |
| Download: ML19344A408 (8) | |
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e.O~r REPORT ON CRITERIA AND METHODOLOGY FOR DIE EVALUATION OF OUT-OF-PLANE LOADING ON MASONRY WALLS AT THE TROJAN POWER PLANT Submitted to:
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Brookhaven National Laboratory Upton, N.Y.
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t by Dr. James Colville, P.E.
Consultant July, 1980 soos200M b t
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Introduction Since submitting the Report on " Design Criteria for Masonry Walls in the Trojan Power Plant" in March, 1980 and the subsequent three reports in April,1980 a considerable amount of discussion has centered on the appropriate criteria and methodology for the evaluation of out-of-plane loading on all masonry walls at the Trojan Power Plant.
A number of different types of walls exist at the Plant. These may be categorized as follows:
l a) Single wythe walls b) double wythe heavy weight block walls c) double wythe light weight block walls d) composite masonry walls On June 10, 1980, Portland General Electric Company submitted Supplement 4 to Licencee Event Report (LER) 79-15 which presenter. a proposed criteria and methodology for the evaluation of out-of-plane loads on double wythe heavy weight block walls.
Subsequently, and after meetings held on June 19-20 and June 25-28, 1980 with NRC Staff, Supplement 4 was revised and extended in scope to cover all masonry wall types listed above.
This report summarizes my comments on these revisions and my observations concerning the overall interim criteria to be used to evaluate the adquacy of all masonry walls.
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11 Review of Developed Criteria The criteria developed on June 28, 1950 for evaluation of all masonry walls is, in my opinion, adequate to ensure the integrity of all valls having safety significance, as defined in Attachnent 2 of the June 28, 1950 sub=ittal.
Although there are a considerable nu=ber of iters relating to the casonry wall proble=, the more significant of these are listed below:
(1) Identification of walls having safety significance I
(2) Magnitudes of interstory displace =ents throughout the co: plex.
(3) Material properties for stiffness evaluation (4) Material properties for capacity evaluation (5) Allowable stresses for walls, including:
a) heavy weight double wythe walls b) standard weight double wythe walls c) single wythe walls d) corposite walls (6) Calculation nethodology for determining collar joint shear bond stresses in double wythe walls.
(7) Stiffness considerations for energy balance technique for walls failing to meet the accepted criteria (S)
I= pact of wall response on attached safety related syste=s (9) Method of modifying walls that fail to =eet the accepted criteria Before briefly reviewing the above, it is i portant to state the philosophy of the criteria.
In essence, the criteria addresses the casonry wall proble: in two stages:
and (1) walls which cust be codified prior to start-up of the plant, (2) walls which can be codified by October 31, 1950 during plant operation.
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3 In my opinion, considering the relatively minor variations in the criteria for identifying walls which must be modified prior to start-up and the deadline for modifyirg all walls having safety significance, this apprcach is rational and reasonable.
(1)
Identification of Walls having Safety Significance The criteria stated in Attachment 2 for identifying walls having safety significance is considered appropriate.
(2) Amplification Factors for Interstory Displacements The procedures followed in Attachments 3 and 4 for determining the displacement amplification factors and displacement profiles through-out the Complex seem complete and adequate.
However, the detailed pro-cedure and associated numerical values developed have not been reviewed since this is beyond the scope of my past involvement with NRC Staff.
It should, however, be noted that the information contained in these attachments are for interim use only and will be replaced by information currently being developed by Bechtel using a finite element computer algorithm which has some capability of modeling nonlinear effects caused by degradation of the shear walls under in-plane loadings.
(3) Material Properties for Stiffness Evaluation (Table 3-2)
The values for modulus of elasticity of the various materials are acceptable as given. The major revision to this Table concerns the development of modulus of rupture ranges for the various materials listed.
Although the use of a range of modulus of rupture values is awkward and it would be preferable to have single values available for use, I concur that, because of the complex nature of the analytical problems
4 associated with the masonry walls, upper and lower bounds values are needed.
In the absence of sufficient test data to better quantify the modulus of ruptures and tensile bond strengths of the materials used, I believe that the ranges listed in Table 3-2 represent reasonable estimates of the variability of these properties.
Also the use of 80 psi as de-scribed in Note 2 is acceptable.
(4) Material Properties for Capacity Evaluation (Table 3-3)
The values given in Table 3-3 are satisfactory.
(5) Allowable Stresses for Walls The allowable stresses given in Tables 5-la, 5-Ib, 5-Ic, and 5-Id, are in my opinion, satisfactory for use at present. However, it should be pointed out that the collar joint shear stress values of 10 psi for heavy weight double wythe walls, and 20 psi for standard weight double wythe walls are based on a limited number of tests performed on in-situ walls at the Complex. Also the test procedure from which these values i
have been developed is subject to question.
In summary, these values i
are in my opinion appropriate as interim criteria, although it is recom-mended that further testing be conducted as soon as possible to validate j
these values.
In the meantime the immediate use of 12 psi and 24 psi for j
heavy weight and standard weight double wythe walls, respectively,that will l
l be accessible for modification during plant operation is acceptable, in l
my opinion.
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j (6) Calculation Methodology for determining Collar Joint Shear Stresses l
l The general methodology outlined in Supplement 4, Section 6.1.1 L
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5 for calculation of the collar joint shear stress in double wythe walls is valid and proper.
(7) Stiffness Considerations for Energy Balance Technique The procedure described in Attachment 6 outlining the method of determining the stiffnesses used to obtain wall deflections is reasonable and consistent.
(8)
Impact of Wall Response on Attached Safety Related Systems The use of the energy balance technique on walls in which the mid-span reinforcement strains exceed three times the yield strain and the requirement that an evaluation of the impset of wall flexibility on attached safety related systems of walls having a structural frequency of less than 20 Hz are, in my opinion, necessary elements of the criteria.
(9) Method of Modifying Walls The use of mouifications based only on alternatives 3 and 4 of Sup-plement 4 to LER 79-15 is acceptable.
In other words, Alternatives 1 and 2 of Supplement 4 to CER 79-15 should not be used to modify walls failing to meet the criteria.
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6 III Margin of Safety Since I have not reviewed the estimated in-plane capacity to load ratios of the numerous shear walls in the Complex, the overall margin of of safety existing in the Complex is impossible for me to assess. How-ever, I believe that the procedure outlined previously in my initial report on " Design Criteria for Masonry Walls in the Trojan Power Plant" for determining in-plane capacities of shear walls provides a reasonable basis for establishing an upper bound estimate of the margin of safety 1
when compared to the results of an appropriate analysis of the structural system.
The estimated margin of safety based on such a comparison should, in my opinion, be considerably larger than unity since factors such as, but not limited to, quality of original workmanship, variability of material properties, current structural condition of the walls, and the difficulty of accurately modeling the complex response of the struc-ture in a post cracked condition may combine to significantly reduce the theoretical safety margin.
With respect to out-of-plane margins of safety of masonry walls the following coments are presented:
(1) All safety related walls conforming to the allowable stress criteria set forth in Supplement 4, as modified, will have a safety margin estimated, in my opinion, to be approximately 2.0.
i (2) All multiple wythe walls in which the interface stress criteria l
are violated run a considerable risk of serious structural damage.
(3) Other walls having stresses in excess of the allowable values given in the criteria will have margins of safety which may be less than 2.0, and depending on the magnitude and t17e of over-stress may also experience structural damage.
In partt:ular, walls having strains in excess of the yield strain due to out-of-plane inertia loadings, will be permanently damaged and will,
7 in ny opinion, need to be subsequently strengthened or re-placed. The extent of this damage will depend on the magnitude r f the wall deformations.
e (4) Since the criteria requires the modification of walls in which safety related systens would be adversely affected by over-stress or delamination of multiple wythe walls, damage to in-dividual walls should not adversely affect the safety of the Plant. However, I do not feel campetent at present, to comment with assurance on the validity of the procedures established in the criteria for assessing whether or not safety related systems would be impacted.
But the use of the energy balance technique with a factor of two applied to the computation of wall displacements would appear to give a conservative basis for evaluating the impact of wall deformations on safety re-lated systems.
IV Summary In sum =ary, in my opinion, the criteria and methodology outlined in Supplement 4, as modified, represent a rational application of structural engineering principles tempered with reasonable estimates of material properties existing in the Complex However, it is recommended that collar joint shearing bond stress values be verified by additional testing.
The overall margin of safety of the Complex cannot be assessed at present, although it is believed that wall damage can result from an L
l SSE earthquake. Proper implementation of the criteria, however, should I
j limit and control this dan.ge such that safety related systems will not be advereely impacted.
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T Jurie 28, 1980 Trojan Nuclear Plant License NPP-1 DonacJ Broehi Assis:a-a Vce Pescent Docket 50-344 H. Engelken, Director Mr. R.
S. Nuclear Regulatory Commission U.
Region V Suite 202, Walnut Creek Flaza 1990 N. California Blvd.
Walnut Creek, CA 94596
Dear Mr. Engelken:
4 to LER 79-15, which contained the pro-posed criteria to be used in the analysis of the out-Supplement No.
of-plane behavior of heavyweight double wythe masonry walls, was submitted to you by my letter dated June 10,In i
the NRC Staff agreement was reached on revised criter a, 1980.
which have been expanded in scope to include all masonryThe enclosed attachm walls having safety significance.
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and tables reflect the agreed-upon revisions to the cr all masonry walls in As also agreed to at the meetings, i
d the Plant will be evaluated in 'accordance with the rev se except that,the allowable collar joint shear stress for standard weight and heavyweight double wythe
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walls in areas which are accessible during Plant operat on shall be 24 psi and 12 psi, respectively.
Based on the results of these evaluations the following actions will l
be taken prior to resumption of power operation for wallssatisfy the criteria:
having safety significance which do not For multiple wythe, walls for which the interface stress criteria are exceeded, wall delam,ination 1) will be assumed and a determination will be made as to whether the assumed delamination wouldadv attached to the wall or in its area of (2 feet) in accordance with "3)" below.
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DUPLICATE DOCUMENT Entire docums..c previously entered into system under:
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