ML20053E558
| ML20053E558 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 06/01/1982 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML20053E550 | List: |
| References | |
| 00072090, 72090, NUDOCS 8206090018 | |
| Download: ML20053E558 (7) | |
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4 ATTACHMENT Ir-2 TO 4
TECHNICAL REPORT STRUCTURAL STRESSES INDUCED BY DIFFERENTIAL SETTLEMENT OF THE DIESEL GENERATOR BUILDING 1
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l 00072000 MIDLAND PLANT UNITS 1 AND 2 ANALYSIS OF DIESEL GENERATOR BUILDING FOR ZERO SPRING CONDITION ANALYSIS CONTENTS
1.0 BACKGROUND
1 2.0 ANALYSIS PROCEDt'RE 1
3.0 CONCLUSION
S 2
TABLES 1
Rebar Stress Values for the Diesel Generator Building for Zero Spring Condition FIGURES 1
Diesel Generator Building Finite-Element Model for Zero Spring Condition 2
Comparison of 40-yr Estimated Settlement Values With Settlement Values Resulting From A Finite-Element Analysis of the Zero Spring Condition 11
MIDLAND PLANT UNITS 1 AND 2 OF DIESEL GENERATOR BUILDING ZERO SPRING CONDITION ANALYSIS
1.0 BACKGROUND
During the February 23 through 26, 1982, meeting with the NRC, it was requested that a finite-element analysis of the diesel generator building (DGB) be performed for the 40-year, dead load case, modified with zero and near-zero soil spring constants in areas to represent potential bridging.
The primary purpose of this analysis would be to investigate the structure's ability to span any soft soil condition.
It was subsequently decided that, in an attempt to approximate the predicted 40-year settlement profile of the south wall (as proposed by Dr. Affifi on February 23, 1982), a soil spring value of zero would be used at the junction of the south wall and east center wall.
Soil spring values would then be linearly varied so that springs returned to their original 40-year values within a distance of approximateJy 15 feet from the zero spring (see Figure 1).
2.0 ANALYSIS PROCEDURE A finite-element analysis of the DGB was therefore performed using 40-year soil spring values, modified along the south wall and east center interior partition wall as described above.
Several analysis iterations were necessary to arrive at a settlement profile that approximated the desired "best fit" settlement profile (as obtained from a statistical analysis of Dr. Affifi's estimated 40-year settlement values).
Figure 2 gives an isometric presentation of Dr. Affifi's 40-year settlement values and also the settlement values re-sulting from the finite-element analysis of the DGB for the zero spring condition.
Subsequent to the final analysis iteration, maximum rebar stress values were calculated for the dead load plus settle-ment case (i.e., " modified case").
These values were com-pared with the dead load plus settlement case previously calculated for the " unmodified" 40-year settlement case (see Table 1).
Such a comparison shows that, except for an increase in the south wall, the footings, the box missile shield, and the south shield wall, the maximum rebar stress values remained essentially unchanged.
Typically, stress level increases were limited to approximately 5 ksi except in the south shield wall, where the modeling technique causes the rebar stress value to increase 18 ksi, and in the footings where the nature of the analysis causes the rebar stress value to increase approximately 20 ksi.
1 1
Midland Plant Unito 1 and 2 Diesel Generator Building 000g2000 zero Spring Condition Analysis As a result of this favorable comparison, it is apparent that it would be unnecessary to combine the " modified" 40-year settlement case with other load cases to form the load combinations of the FSAR and the response to Question 15 of the NRC Requests Regarding Plant Fill.
For comparative purposes, the last column of Table 1 also presents maximum rebar stress values for the governing load combinations of the FSAR and Question 15.
A review of this table indicates that settlement stress is typically only a small portion of the overall maximum rebar stress values associated with the required load combinatione (FSAR and Question 15).
Furthermore, because the maximum settlement stresses and maximum service load stresses generally do not occur at the same location, the component of settlement stress that actually exists in a maximum rebar stress value would typi-cally be less than the values of Table 1.
3.0 CONCLUSION
S As a result of the analysis performed, it can therefore be concluded that the DGB can successfully span the assumed sof t soil spot introduced into the analysis without significantly increasing the rebar stress levels.
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Midland Plant Unita 1 cnd 2 Diccol Ganorator Building Zero Spring Condition Analysis 00012090 TABLE 1 REBAR STRESS VALUES FOR THE DIESEL GENERATOR BUILDING FOR ZERO SPRING CONDITION Category Tensile Rebar Stress Values (allowable = 54 ksi)
(D + T)
(D + T)
Max Rebar for for Stresses Unmodified Modified for'FSAR 40-Year Case 40-Year Case and 0 15*
West wall 2.15 2.78 25.03 South wall 6.82 10.98 44.04 Sicb at el 664' 16.94**
16.97**
39.15 Roof at el 680'-0" 5.61 6.19 36.06 South misuile shield 10.79 28.82 42.79 Interior missile shield 5.51 5.30 28.06 North missile chield 2.71 2.72 13.85 Ecot wall 2.24 2.80 23.64 North wall 3.85 4.26 21.90 Interior partition wall 3.71 4.01 16.66 Box missile shield 4.50 9.33 8.02 Footings 14.35 37.14 20.95 (longitudinal bending)
Consists of FSAR load combinations and load combinations contained in response to Question 15 of the NRC Requests Regarding Plant Fill A large portion of this value is attributable to the dead load component.
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MIDLAND PLANT UNITS I AND 2 DIESEL GENERATORS BUILDING ANALYSIS FOR ZERO SPRING CONDITION REFERENCE SURFACE T
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1.15 1.19 1.18 1*29 8
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1.98 CALCULATED SETTLEMENTS (inches)
ACTUAL MEASURED SETTLEMENTS FROM SEPT.14,1979 TO DEC. 31,1981 PLUS
-O-ESTIMATED SECONDARY COMPRESSION SETTLEMENT FROM DEC.31,1981 TO DEC.31,~2025 ASSUMING SURCHARGE REMAINS IN PLACE.
COMPARISON OF 40-YEAR ESTIMATED SETTLEMENT VALUES WITH SETTLEMENT VALUES RESULTING FROM A FINITE ELEMENT ANALYSIS OF Tile ZERO SPRING CONDITION FIGURE 2
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