ML20010G992

Procedure to Account for Out-of -Plane Interstory Drift Effects on Masonry Wall Evaluation.

ML20010G992
Person / Time
Site:	Point Beach
Issue date:	09/30/1981
From:	COMPUTECH ENGINEERING SERVICES, INC.
To:
Shared Package
ML20010G963	List: ML20010G962 ML20010G974 ML20010G981 ML20010G988 ML20010G992 ML20010G998
References
IEB-80-11, PROC-810930, R553.11, TAC-42896, TAC-42897, NUDOCS 8109220752
Download: ML20010G992 (6)

Text

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ACTION ITEM 11 PROCEDURE TO ACCOUT FOR OUT-OF-PLANE INTERSTORY DRIFT EFFECTS ON THE MASONRY WALL EVALUATION Prepared for Point Beach Nuclear Power Plant, Units 1 and 2 WISCONSIN ELECTRIC POWER COMPANY Milwaukee, Wisconsin l

Prepared by COMPUTECH ENGINEERING SERVICES, INC.

Berkeley, California September,1981 REPORT NO. R553.11 8109220752 810915 PDR ADOCK 05 LOO 266 G PD3

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TA8W OF CONTENTS i

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i 1 INTROD UCTIO N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 1 1

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! 2 ANALYSIS METHODOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 i

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3 RESU LTS . . . . . . . . . . . ........................... 2 i

e 4 DISCUSSION OF RESULTS ............................. 2 j

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! C O N C LU SIO N S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 INTRODUCTION The Nuclear Regulatory Commission (NRC) staff on June 9-11, 1981 reviewed the criteria and calculations performed on IE Bulletin 80-11 " Masonry Wall Design" for the Point Beach Nuclear Power Plant. Action item 11 resulting from the review meeting stated that the licensee shall provide the criteria and procedures to account for the out-of-plane Interstory drift effects in seismic analysis.

This short report is in response to that action item and includes a description of the analysis methodology, the results, a discussion of the results, and the conclusions.

2 ANALYSIS METHODOLOGY All walls were analyzed in accordance with the procedures given in ' Criteria for the Re-evaluation of Concrete Masonry Walls for The Point Beach Nuclear Power Plant.' Specifically. In assess the out-of-plane response of the walls the boundary conditions at all supports were assumed to be pinned.

Thir, assumption was made for the following reasons.

(1) The stresses resulting from out-of-plane seismic and equipment loads is conservative.

(2) The boundary rotations required for the existence of pinned supports are very small and will exist regardless of what type of fixity is used to prevent it. A field inspection of the walls Indicated this was the only reasonable assumption.

(3) The majority of the walls had no support at the top of the wall. In addition no support was assumed around any door or other opening.

In assessing the effect of out-of-plane drif t effects on the walls the same assumption of pinned boundary conditions was used for consistency in the analytical procedures. With this assumption no forces are induced in the walls when out-of-plane Interstory drift effects are assessed. The validity of this assumption was questioned in Action item 11 and as a result two walls (Wall Nos. 24 and 65-1) were selected to compare the results that would be obtained if fixed rather than simply supported boundary conditions had been assumed. Wall No. 24 is 164 inches long and 156 inches high and Wall No.

65-1 is 109 inches long and 176 inches high. Each wall is double wythe and was analyzed as a single and double wythe wall with both fixed and simply supported boundary conditions. For the fixed boundary conditions the effects of out-of-plane interetory drift were included in the analysis. The stresses resulting from out-of-plane seismic and equipment loads were combined absolutely with those resulting f rom out-of-plane drif t effects.

Out-of-plane drif t effects were calculated by imposing the out-of-plane displacement at the top of the wall with the wall fixed against rotation at both the top corners and the bottom of the wall.

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3 MSULTS A summary of the maximum stress ratios resulting from the eight analyses performed are given in Table 1. Care must be exercised in evaluating the results because the maximum stresses do not fall in the same region of the wall for the different boundary conditions. In the case of the simply supported boundary conditions the maximum stress ratios are towards the center of the wall and for the fixed boundary conditions they are close to or adjacent to the boundaries.

4 DISCUSSION OF NSULTS The results for Wall 65-1 Indicats that the maximum stress ratios of the simply supported boundary conditions for a single wythe wall are conservative when compared with those of the fixed boundary conditions that include out-of-plane interstory drift effects. The maximum stress ratio for this wall occurred on a horizontal strip and was reduced by almost one-half when fixed boundary conditions were used. When the some comparison is made for the double wythe wall, again the maximum stress ratio which was on a horizontal strip, was reduced by almost one-half. However, the maximum stress ratio on the vertical strip Increased from 0.07 to 0.097. In comparing the three analyses: 1) single wythe with fixed boundarles and out-of-plane drift 2) double wythe with simply supported boundaries and 3) double wythe with fixed boundarles and out-of-plane drift; the maximum stress ratios are all less than the ratios obtained from analyzing the wall with the procedures given in the re-evaluation criteria.

! The results for Wall 24 are similar to those of Wall 65-1 in that the maximum i

stress ratios on a horizontal strip decrease when fixed boundary conditions and out-of-plane drift are considered. However, on a vertical strip the maximum stress ratios increase for Wall 24. The increase for the single wythe wall is from 0.156 to 0.209 and for the double wythe wall it is from 0.075 to 0.226.

Although this increase for Wall 65-1 Indicates that for a vertical strip, the simply supported boundary conditions is non-conservative the governing stress ratio on the horizontal strip is not exceaded by the maximum i

stress ratios in either direction for the other three analyses. Therefore, in this l

regard the assumption of slmply supported boundary conditions used in the re-evaluation criteria can be considered conservative.

5 CONCLUSIONS The criterla and procedures used to account for out-of-plane Interstory drift effects in the re-evaluation criteria have been described and compared with l

resluts obtained from an alternate approach. In summary, the procedure used in the re-evaluation criteria assumes the walls have pinned supports at the j

boundarles because it is our opinion that this is the mest realistic representation of field conditions and in addition it results in a conservative estimate of the stresses resulting from out-of-plane selsmic and equipment j loads.

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Two walls were selected to compare the maximum stress ratios obtained from the assumptions used in the re-evaluation criteria with those obtained from using the assumption that the top and bottom boundarles had fixed supports.

The stresses obtained for the out-of-plane forces acting on the wall with fixed boundary cnnditions were added absolutely to those resulting from out-of-plane drift effects.

For the two walls that were analyzed, the maximum magnitude of the Stress ratio was obtained for the single wythe wall with simply supported boundary conditions. In both cases this was the stress on a horizontal strip. In this regard the assumptions used in the re-evaluation criteria are conservative.

For Wall 65-1 the maximum stress ratio on both a horizontal and vertical strip obtained from the single wythe wall with simply supported boundary conditions were conservative. For Wall 24 the same statement is valid for the maximum ctress ratio on a horizontal strip. For the maximum stress ratio on a vertical strip there was an increase when fixed boundary conditions were used but this increase did not exceed the maximum stress ratio obtained on the horizontal strip.

From the results presented it is clear that the impact of different boundary conditions varies and is difficult to accurately assess because the region where the maximum stress occurs changes as the boundary condition changes. However, for the two walls analyzed the assumption of a single wythe wall with simply supported boundary conditions (i.e. that used in the re-evaluation criteria) produces the maximum magnitude in the stress ratio on either a horizontal or vertical strip. Furthermore, it is our opinion that these boundary conditions are the most realistic for the conditions that exist in the field.

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TABLE 1 MAXIMUM STRESS RATIOS FOR VARYING BOUNDARY CONDITIONS Uall No. Thickness (in) Condition Mx /Mxa My/Mya 12 Simply Supported 0.373 0.156 12 Fixed, Drif t 0.244 0.209 24 25 Simply Supported 0.181 0.075 25 Fixed, Drift 0.129 0.226 6 Simply Supported 0.483 0.157 6 Fixed, Drift 0.264 0.136 65-1 -.

12 Simply Supported 0.215 0.070-12 Fixed, Drift 0.117 0.097 Note: Subscripts x and y denote stress ratios on horizontal and vertical strips respectively i

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