applicability evaluation of steel plate reinforced

Transactions, SMiRT-23

Manchester, United Kingdom - August 10-14, 2015

Division V, Paper ID 258

APPLICABILITY EVALUATION OF STEEL PLATE REINFORCED

CONCRETE STRUCTURE TO PRIMARY CONTAINMENT VESSEL OF

BWRS

(3) COMPRESSIVE LOADING TEST OF STEEL PLATE

REINFORCED CONCRETE STRUCTURE UNDER HIGH

TEMPERATURE CONDITIONS

Shintaro Narita1, Masaaki Osaka

2, Tomohisa Kurita

3, Tomohiro Kobayashi

4,

Norichika Kakae5, Yoshihisa Kobayashi

6

1 Staff Engineer, Hitachi-GE Nuclear Energy, Ltd. Japan 2 Manager, Hitachi-GE Nuclear Energy, Ltd. Japan 3 Senior Manager, Toshiba Corporation, Japan 4 Senior Engineer, Kajima Corporation, Japan 5 Senior Research Engineer, Kajima Corporation, Japan 6 General Manager, Tokyo Electric Power Company, Inc. Japan

ABSTRACT

Since the steel plate of steel plate reinforced concrete containment vessel (SCCV) is directly exposed to

high temperature under accident conditions, thermal thrust that may cause buckling of steel plate is

generated. In this study, compressive loading tests of steel plate reinforced concrete (SC) specimens

under high temperature up to 200°C were conducted in order to obtain the compressive property of SC

structure. The buckling of steel plate is not observed under the vertically restrained condition until 200°C.

After the continuing compressive loading that causes steel plate buckling, specimens reach maximum

compressive strength. Simulation analysis using elasto-plastic finite element analysis code was

conducted, and it was confirmed that analyses could simulate the buckling behavior of steel plate. The

relationship between ratio of stud pitch to steel plate thickness and the steel plate strain at the time of

buckling under high temperature is examined.

INTRODUCTION

Steel plate reinforced concrete containment vessel (SCCV) is directly exposed to high temperature under

accident conditions. To evaluate the applicability of SC structure to Primary Containment Vessel (PCV),

it is required to confirm the compression resistance of SC structure and the behavior of the buckling of

steel plate in high temperature environment. The test purpose is to collect data for the evaluation of load-

displacement relationship, and for the understanding the phenomenon of yield and buckling of steel plate

under high temperature environment.

23rd Conference on Structural Mechanics in Reactor Technology


Division V

EXPERIMENTAL DETAILS

Specification of the test specimen

The test specimen is a partial model of the internal surface of SCCV wall (the side exposed to high

temperature). It is modelled in 1/2 scale of the expected actual structure. Figure 1 shows the

configuration of the test specimen. Figure 2 shows the shape of the test specimen. As shown in Figure 1

the test specimen has test portions at both sides arranged symmetrically, and fixed upper and lower ends

with Reinforced Concrete (RC) stubs for the force application. The test specimen is heated from both

sides.

The steel plate is made of SPV490 (JIS G 3115: Yield stress:490MPa, Ultimate strength:610MPa), which

is a proven primary containment material in Japan. The specified design compressive strength of concrete

is 33N/mm2, which is the same as RCCV (Reinforced Concrete Containment Vessel), which has

operational experiences in Japan. The material age of concrete for test specimen is more than 91days.

Figure 1. Configuration of the test specimen. Figure 2. Shape of the test specimen.

Test parameters

The test parameters are temperature, heating duration, stud pitch, restraint conditions when heating, and

compression loading method. Table 1 shows the test matrix set, considering the following parameters (1)

through (4).

(1) Temperature conditions

The temperature conditions in this test are set based on the assumed temperature conditions under design

basis accident (DBA) and severe accident (SA) of SCCV. Assuming short-term has passed after accident,

the test case of 175 is set. In this condition, temperature difference between surface of steel plate and

concrete is large. Assuming long-term has passed after accident, the test cases of 145 and 200 are set.

In these conditions, the steel plate and concrete are both under high-temperature conditions. In addition,

to evaluate the effect of heating history, one heat removal case is also set. The test specimen of heat

removal case is cooled after 145 heating.

Partial Scale model

Specimen

100mm 200mm

Fc331/2(Scale down)SymmetricalArrangement

Plate

(6mm thick)

SCCV

Fc33

Heat

2000mm

200mm

Inside Plate

12mm thick

Surface Part

200mm thick

Heat Heat Heat

:Test part

RC stub

RC stub

Front side Back side

Tie bar!5@63

(

Front View Cross Section(B-B’)

D19@125

PL6.0PL6.0

D19@125

Tie bar!5@63

B

B’

PL20 PL6.0

300550

1150

300 200 200 200

600

Stud!9@120

(L=72)

@120 3

=360

@120

5=

600



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(2) Stud pitch

The buckling of the steel plate constituting the SC structure depends on the ratio of the stud pitch (B) and

the steel plate thickness (t). In this test, B/t=20 is set as the standard. In previous studies, elastic buckling

does not occur when steel plate’s B/t is equal to 20 under high temperature. However, to obtain the data

for the rationalization study of the stud number, B/t=30 case is also set.

(3) Restraint conditions when heating

In this test, after the test specimen is heated to a predetermined temperature, the compressive force is

planned to be loaded. Two cases of restraint conditions when heating are considered: a) case of

restraining the thermal displacement of the test specimen while heating (“Fixed” condition) and b) case of

not restraining the thermal displacement of the test specimen while heating (“Free” condition). Since the

main purpose of this study is to understand the behavior of steel plate with thermal strain, and

compressive buckling, the “Fixed” cases are set as the standard. To evaluate the effect of restraint

conditions, one “Free” condition case is also conducted.

(4) Compression loading method

To confirm the condition of the steel plate at each load level set in steps and the tendency of stiffness

when unloading, cyclic compressive load is applied to the test specimen. To evaluate the effect of

loading methods, one monotonic loading case is conducted.

Table 1: Test matrix.

No.

Temperature conditions B/t Restraint

conditions Loading method

Room

temp. 175

Short term

145

Long term

200

Long term20 30 Fixed Free Cyclic Monotonic

1 X - - - X - - - X -

2 - - X - X - X - X -

3 - X - - X - X - X -

4 - X - - X - - X - X

5 - X - - - X X - X -

6 - - - X X - X - X -

7 - - X *1 - X - X - X -

*1: Heat removal case.

Test Method

In this test, after the test specimen is heated to a predetermined temperature, the compressive axial force

is loaded. (During the loading of compressive force, the temperature of test specimen is maintained.) By

using an electric heater, the test specimens are heated until the temperature distribution in the cross

section becomes the same as the temperature distribution of the assumed SCCV wall. After above initial

heating, the compressive load in the axial direction is applied on test specimen using two hydraulic jacks

capacity of 10,000kN, through the RC stub which is provided at the upper and lower ends of the specimen.

The test specimen is shown in Figure 3. The heating and compressive loading apparatus is shown in

Figure 4. In the cyclic load test, the loading sequence as shown in Figure 5 is applied to the test specimen.



Division V

Figure 3. Test specimen. Figure 4. Heating and compressive loading apparatus.

Loading end

(Max. load)

Start loadingTime

Compressive load

Heating end

Reach the target temperature

distribution condition

TimeStart Heating

Temperature

Heating Sequence

Loading Sequence

Test temperature

Figure 5. Test procedures.

Measuring Method

In order to detect the buckling of the steel plate, the strains at representative parts of steel plate, stud and

tie bars are measured using strain gauges. Furthermore, thermocouples are arranged to measure the

temperature distribution of steel and concrete in the specimen.

RC stub

RC stub

Test Specimen

(SC Wall)

Test Specimen

& Heater

Hydraulic Jacks

(2 jacks)

Force application Flame



Division V

RESULTS AND DISCUSSIONS

Test Results

Test results are shown in Table 2.

Table 2: Test results.

No. Test

condition

Compressive

strength of

concrete

[N/mm2]

Compressive

load at the

start of the

out-of-plane

deformation

[kN]

Compressive

strain at the

start of the

out-of-plane

deformation*1

[ ]

Maximum

compressive

load

[kN]

Compressive

strain at the

maximum

compressive

load*1

[ ]

1 Room temp. 49.2 8766 3841 9063 4306

2 145 47.6 6798 3194 7575 3711

3 175 51.1 6182 3560 6511 3701

4 175

[Free / Monotonic] 46.3 6417 3288 6789 3594

5 175

[B/t=30] 50.6 3932 1963 5109 2975

6 200 52.1 4073 2505 5604 8699

7 145

[Heat removal] 46.6 8272 3726 8443 3886

*1: Value of strain converted from vertical displacement of the steel plate.

Figure 6 and Figure 7 shows the load-displacement relationship of case No.1 and No.3, as the

representative case.

Figure 6. Load-displacement relationship Figure 7. Load-displacement relationship

of case No.1. of case No.3.

Case No.1 is the cyclic loading test at room temperature. With the compressive load increase, the out-of-

plane deformation of the steel plate occurred, and then compressive load reached the maximum strength.

Case No.3 is the cyclic loading test at high temperature. In step (1), the out-of-plane deformation did not

occur in a state of restraining the thermal displacement of the test specimen. In other high temperature

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

-2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0

Co

mp

ressiv

e L

oa

d (kN

)

Vertical Displacement (mm)

Out-of-plane derformation (Start point)

Maximum Load

Compressive

Loading

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

-2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0

Co

mp

ressiv

e L

oa

d (kN

)

Vertical Displacement (mm)

Out-of-plane derformation (Start point)

Maximum Load

(3) Compressive loading with heat

(1)Heating with restraint

(2) Release restraint

with heat



Division V

conditions, the result was the same. Then in step (2), the restraint of the specimen was released while

maintaining the heating, and in step (3), with the compressive load increasing, the out-of-plane

deformation of the steel plate occurred, and then compressive load reached the maximum strength.

Figure 8 and Figure 9 shows the load-displacement relationship showing load sharing of steel plate and

concrete for the cases described above.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

-2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0

Co

mp

ressiv

e lo

ad

(kN

)

Vertical displacement (mm)

SC structure (Total)

Concrete

Steel plateMax. compressive load

(Concrete)

Buckling

Simple cumulative load

(Concrete & Steel)

Max. strength of SC specimen

Max. compressive load

(Steel plate)

Figure 8. Load-displacement relationship of case No.1 (showing load sharing).

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

-2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0

Co

mp

ressiv

e lo

ad

(kN

)


SC structure (Total)

Concrete

Steel plate Max. compressive load

(Concrete)

Buckling

Simple cumulative load

(Concrete & Steel)


(Steel plate)

Difference in thermal expansion

between the steel and concrete

Max. strength of SC specimen

Figure 9. Load-displacement relationship of case No.3 (showing load sharing).

Figure 8 shows that at room temperature, the maximum strength of SC specimens measured in the test is

approximately equal to the simple cumulative compressive load of steel and concrete. On the other hand,

Figure 9 shows that at high temperature, the maximum strength of SC specimens measured in the test is

lower than the simple cumulative compressive load of steel and concrete. At high temperature condition,

since difference in thermal expansion between the steel plate and the concrete occurs, the load sharing



Division V

ratio of concrete when the out-of-plane deformation of the steel plate occurs is small. As a result, it is

considered that the concept of the cumulative load is not satisfied.

Parametric study

Figure 10 shows the comparison of compressive load-strain relationship in the cases of the temperature

conditions in the test of the B/t=20. The starting point of the out-of-plane deformation of steel plate is

distributed to between 2500! to 4000!, which is the same level as the yield strain of the steel plate (about

3400!). In order to confirm the effects of stud pitch and loading method, a comparison of compressive

load-strain relationship in case 3, 4, 5 is shown in Figure 11. With the expansion of the stud pitch, the

out-of-plane deformation of the steel plate occurs at smaller compressive strain. In addition, since the

compressive stiffness and compressive strength of cyclic loading and monotonic loading are

approximately equivalent, the effects of loading conditions are small. In order to confirm the effects of

heat removal, a comparison of compressive load-strain relationship in case 1, 2, 7 is shown in Figure 12.

Even when applying compressive load after heat removal, the starting point of the out-of-plane

deformation of the steel plate is equivalent to the room temperature case. In addition, the compressive

strength and the deformation characteristics after heat removal show an intermediate property of the test

results at room temperature and high temperature.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2000 4000 6000 8000

Co

mp

ressiv

e lo

ad

(kN

)

Compressive strain (")

No.1(Room temp. B/t=20)

No.2(145 , B/t=20)

No.3(175 , B/t=20)

No.4(175 , B/t=20, Monotonic Loading)

No.6(200 , B/t=20)

Figure 10. Comparison of the results due to the temperature conditions.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2000 4000 6000 8000

Co

mp

ressiv

e lo

ad

(kN

)


No.3(175 , B/t=20)

No.4(175 , B/t=20, Monotonic Loading)

No.5(175 , B/t=30)

Figure 11. Comparison of the results due to the stud pitch and loading method.



Division V

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2000 4000 6000 8000

Co

mp

ressiv

e lo

ad

(kN

)


No.1(Room temp. B/t=20)

No.2(145 , B/t=20)

No.7(145 , B/t=20, Heat removal)

Figure 12. Comparison of the results due to the heat removal.

Analytical approach

The purpose of analysis is to develop the method of analysis which is able to simulate the buckling

behavior of steel plate and compressive load-displacement relationship of SC structure, by comparing

with test results. Using Finite Element Analysis code “ABAQUS Ver.6.9”, the concrete is modelled with

solid elements, and the steel plate is modelled with layered shell elements. The comparison of load-

displacement relationship by analysis with test case No.3 is shows in Figure 13. Although the maximum

strength of the analysis shows greater value than the experiment, the displacements at the out-of-plane

deformation of the steel plate are nearly identical. Figure 14 shows the appearance of the specimen after

the test. Figure 15 shows the deformation shape of analysis simulated in test case No.3. Figure 14 and

Figure 15 show that analysis is able to simulate the buckling behavior of steel plate.

-1000

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Com

pre

ssiv

e load (

kN

)


Test

Analysis

Out-of-plane deformation (Start point)


Figure 13. Comparison of analysis with test.



Division V

Compressive load

Out-of -plane

deformation

Compressive load

Out-of-plane

deformation

Figure 14. Appearance of the specimen (test No.3). Figure 15. Deformation shape of analytical model

(Deformation magnification 5 times).

Evaluation of buckling strain

Figure 16 shows the relationship between “dimensionless strain” normalized by y at out-of-plane

deformation and “dimensionless ratio of stud pitch to steel plate thickness” normalized by ( y/E).

These plots represent the results of test. The relationship between compressive strain at out-of-plane

deformation of the steel plate and B/t is approximately equal to the Euler equation for column buckling.

(One end fixed, other end pinned.)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

Dim

en

sio

nle

ss s

tra

in: #

cr/#y

Dimensionless ratio of stud pitch to steel plate thickness: B/t $%y/E

Euler equation

Room temperature

145

175

200

145 -Heat removal

Figure 16. Relationship between dimensionless strain at out-of-plane deformation

and dimensionless ratio of stud pitch to steel plate thickness.



Division V

CONCLUSION

From the results of this study, the following conclusions are obtained.

- Up to 200 , the out-of-plane deformation of the steel plate did not occur in a state of

restraining the thermal displacement of the test specimen. After that, with compressive load

increasing, the out-of-plane deformation of the steel plate occurred, and compressive load

reached the maximum strength.

- Elastic buckling did not occur when steel plate’s B/t is equal to 20 under high temperature.

With the expansion of the B/t up to 30, the out-of-plane deformation of the steel plate occurs

at smaller compressive strain.

- The strain at out-of-plane deformation obtained by Finite Element Analysis, and the test

results matched mostly. It was confirmed that analyses could simulate the buckling behavior

of steel plate.

- The relationship between compressive strain at out-of-plane deformation of the steel plate

and B/t is approximately equal to the Euler equation for column buckling. (One end fixed,

other end pinned.)

ACKNOWLEDGEMENTS

This work was carried out during FY2008-2010 as Japan national project “Development of Innovative

Construction Method (SC Structure)” with the participation of Tokyo Electric Power Company, Inc.,

Tohoku Electric Power Company, Inc., Chubu Electric Power Company, Inc., Hokuriku Electric Power

Company, Inc., The Chugoku Electric Power Company, Inc., The Japan Atomic Power Company,

Electric Power Development Company, Ltd., the Institute of Applied Energy, Toshiba Corporation and

Hitachi-GE Nuclear Energy, Ltd.

We would like to thank Dr. T. Nishikawa, a Professor Emeritus at Tokyo Metropolitan University, Dr. K.

Takiguchi, a Professor Emeritus at Tokyo Institute of Technology, Dr. Y. Kitsutaka, a Professor at Tokyo

Metropolitan University, and Dr. I. Maruyama, an Associate Professor at Nagoya University for valuable

discussions.

applicability evaluation of steel plate reinforced

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