ML20038C282

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Addendum to Technical Rept on Underpinning Auxiliary Bldg & Feedwater Valve Pits
ML20038C282
Person / Time
Site: Midland
Issue date: 12/02/1981
From:
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML20038C281 List:
References
NUDOCS 8112100357
Download: ML20038C282 (14)
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ADDENDUM TO TECHNICAL REPORT ON UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS CONSUMERS POWER COMPANY MIDLAND PLA'iT UNITS 1 AND 2 DECDGER 2,1981 ffj2100357811203 ADOCK 05000329 A

PDR

f' MIDLAND PLANT UNITS 1 AND 2 ADDENDUM TO TECHNICAL REPORT ON UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS CONTENTS

1.0 INTRODUCTION

1 2.0 SOIL PRESSURES 1

3.0 UNDERPINNING WALL DESIGN 3

4.0 STABILITY 4

5.0 CONNECTION DETAIL 4

6.0 EXISTING STRUCTURE 4

REFERENCES l

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r MIDLAND PLANT UNITS 1 AND 2 ADDENDUM TO TECHNICAL REPORT ON UNDERPINNING THE AUXILIARY BUILDING AND FEEDWATER ISOLATION VALVE PITS

1.0 INTRODUCTION

The purpose of this addendum is to supplement Section 7.5 of the Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits (Reference 1) with the following information:

a.

Soil pressure data under the auxiliary building, feedwater isolation valve pits (FIVPs), and auxiliary building underpinning b.

Load combinations used for preliminary design of the underpinning reinforcement and the connection of the underpinning to the auxiliary building c.

Design forces and moments at the design sections d.

Reinforcement provided in the underpinning walls e.

Identification of the areas of potential overstress in the auxiliary building as indicated by the preliminary analysis The material presented herein is based on preliminary analyses and design for the permanent underpinned configuration of the auxiliary building and the FIVPs.

Detailed checking will be performed after final analysis to verify the design adequacy.

The results of this detailed check will be provided later in an audit scheduled for May 17, 1982.

The results of the analysis for the construction condition with temporary support piers are not included.

This analysis is in progress and the results will be provided later for the audit scheduled January 15, 1982.

2.0 SOIL PRESSURES l

2.1 AUXILIARY BUILDING UNDERPINNING Table.1 and Figure 1 show the magnitude and location of the net soil pressure under the main auxiliary building and underpinning under the control tower and the electrical penetration area.

The soil pressures were computed for the following load combination considered to be critical for preliminary analysis.

D+L+R+E' +P g

where D = dead load 1

Midland Plant Units 1 and 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits L = live load R = pipe break load E' = safe shutdown earthquake (SSE) loads corresponding to the ground acceleration given in the Midland FSAR Section 3.7 This load combination corresponds to the 19th load combination in Table 1 of Reference 1 without the thermal loads which are neglected in the preliminary design.

The allowable net bearing pressure is based on the allowable values submitted to the NRC in Subsection 7.2.1 of Reference 1 and Midland FSAR Section 2.5.

2.2 FEEDWATER ISOLATION VALVE PITS The FIVPs will be supported on engineered sand backfill.

A 3-foot thick concrete slab will be provided between the bottom of the pit and the top of the sand, as shown in Figure 2.

The sand will be confined between the reactor building, electrical penetration area underpinning wall, turbine building underpinning, and buttress access shaft.

The slab at the top of the engineered backfill will be jacked against the existing FIVP base slab.

This jacking will minimize any future settlement due to compaction of the engineered backfill from the weight of the FIVP.

After jacking, the space between the 3-foot slab and the bottom of the pit will be filled with concrete grout.

The maximum bearing pressures on the engineered backfill are shown in Table 2.

The soil pressures (shown in Table 2) were computed for the following critical load combination considered in the preliminary analysis:

D + L + E' +Pg This load combination corresponds to the 19th load combination in Table 1 of Reference 1 without the thermal loads which are neglected in the preliminary design.

2 1

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Midlcnd Plant Unito 1 cnd 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits 3.0 UNDERPINNING WALL DESIGN 2.1 LOADS The preliminary wall design is based on the following loads and load combinations:

a.

U = 1.4D + 1.7L + Pg(corresponds to the fifth case in Table 1 of Reference 1) b.

U = 0 + L + R + 1.5E' + Pg For the above load combinations, the following loads have been considered:

a.

Dead load - Includes soil pressure loads.

b.

Jacking load applied as uniform load along the length of the underpinning c.

Live load d.

Seismic loads e.

Pipe break loads 3.2 UNDERPINNING BELOW THE ELECTRICAL PENETRATION AREA The underpinning wall under the electrical penetration areas will carry the vertical loads which will be transferred to clay till at el 571'.

The walls will also carry lateral loads due to seismic forces, soil pressure, and surcharge from the turbine building.

These lateral loads will be resisted by the engineered sand backfill placed between the underpinning wall and the reactor building, as shown in Figure 4, and the friction between the concrete wall and the soil underneath (clay till).

The net lateral loads in the second load combination exceed the available friction between the wall and soil.

For this reason, an ll-foot wide, horizontal beam has been provided to resist the bending due to the net lateral loads (Figure 4).

The critical section for the wall is near column lines 5.3 and 7.8 (see Figure 3).

The design forces are shown in Table 3 and reinforcement is presented in Figure 3.

3 i

Midland Plant Unita 1 and 2 Addendum to Technical Report on Underpinning the Auxiliary Building and Feedwater Isolation Valve Pits 3.3 UNDERPINNING BELOW THE CONTROL TOWER The underpinning wall will be embedded in natural clay till between elevations 571 and 562, and will be restrained by a new slab at el 583'-6" to be constructed as shown in Figure 4.

The space between el 571' and the slab at el 583'-6" will be backfilled with engineered granular material.

Part of the lateral loads will be resisted by the clay till between.

elevations 571 and 562, ar.d the balance will be transferred to the main building by the slab at el 583'-6".

The critical section for the wall is at column'line 7.8.

The location of the critical sections and reinforcement are presented in Figure 3.

Design loads at the critical section are presented in Table 3.

4.0 STABILITY The factors of safety against sliding and overturning are shown in Subsection 3.8.6.3.4 of the Midland FSAR (Reference 2).

In the underpinned condition, the overall safety factors against sliding and overturning are expected to reduce or remain unchanged from the values shown in the Midland FSAR.

5.0 CONNECTION DETAIL

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The connection of the underpinning to the auxiliary building will i

be designed to transfer shear and tension resulting from the seismic lateral loads and other concurrent loads.

The design i

loads are presented in Table 3.

The type and arrangement of l

dowels required for the connection are being finalized and j

will be provided during the structural audits.

At first, the dowels will be grouted only on one side, either at the building or the underpinning.

The other side will be arouted only after jacking loads are applied and held.

To achieve this for the horizontal dowels, the end portion of the underpinning wall will be poured after jacking loads are applied and held long enough for the till to be within secondary compression.

6.0 EXISTING STRUCTURE Based on a preliminary analysis, the following areas between column lines G and H appear to be overstressed:

a.

Slab at el 659' 4

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Midland Plant Units 1 and 2 Addendum to Technical Report on Underoinning the Auxiliary Building and Feedwater Isolation Valve Pits b.

Shear walls on column lines 5.6 and 7.8 between elevations 584' and 614' c.

West staircase wall on column line 5.3 between elevations 646' and 685' d.

Walls on column lines 5.8 and 7.2 from elevations 659' to 699' The above mentioned areas will be structurally upgraded to withstand all loads including 1.5 x E' if the more rigorous final analysis still indicates that these areas are overstressed.

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NET SOIL PRESSURE (XSF)

ULT. NET D+ L+ R + E% P D+L+R+P BEARING u

POINT CAPACITY EL.

CASE 1 CASE 2 (KSF) pr,m3 A

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Case 1 corresponds to maximum compression @ PT. F l

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Case 2 corresponds to minimum compression @ PT. F 3.

Cross soil pressure is given in parenthesis 4.

Compression is negative Note: Net pressure is total pressure CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 minus the pressure due to the AUX BLDG UNDERPINNING SOIL PRESSURE TABLE-1

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SOIL PRESSURE (KSF) i D + L+ E' D+L POINT CASE I CASE 2 CASE 3 A

2.54 2.96

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-10.83

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-7.41

-6.78 4.68 E

0.39 0.85

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1) CASE 1 CORRESPONDS TO MAX. COMPRESSION
2) CASE 2 CORRESPONDS TO MIN. COMPRESSION
3) COMPRESSION IS NECATIVE
4) ULTIMATE BEARING CAPACITY = 25 KSF (ESTIMATED MINIMUM VALUE)

CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 FIVP SOIL PRE S S URES TA B L E - 2 i

UNDERPINNING WALLS IN pt A Ne L OCA TION LOAD A XIA L MOM'T M O M'T SHEA R SHEA R P

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INTERFA CES

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LOCATION A XIA L SHEAR SHEAR IN TERFACE CAR K/F i K/F T gjp 7 HOR /Z 15.7 117 (FIG. 3) b (FIG 1)

YbbI 12.7 79.7 2

LOAD COMBINATIONS:

1.

U = 1.4 D + 1.7 L +Pu 2.

U = D + L + R + 1.5 E'+ Pu NO TE:1)THE CAPACITIES CORRESPOND TO THE EXISTING A XI A L LOADS.

2)+VE AXIAL LOAD IS TENSION 3)THE CRITICAL OUT OF PLANE SHEAR IN THE UNDERPINNING WALL IS 21.3k/ft WHILE THE CAPACITY IS 94k/ft

  • THE TYPE AND SPACING OF DOWELS WILL BE FINALIZED

" CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 Aux. Bldg. Underpinning Design Loads Table 3

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