Study on a concrete filled structure for nuclear power plants

Nuclear Engineering and Design 179 (1998) 209–223

Study on a concrete filled structure for nuclear power plants

M. Takeuchi a, M. Narikawa a, I. Matsuo b,*, K. Hara b, S. Usami b

a Tokyo Electric Power Company, 1-1-3 Uchisaiwaicyo, Chiyoda-ku, Tokyo 100, Japanb Kajima Corporation, Nuclear Structures Engineering Department, A/E 6-5-30 Akasaka, Minato-ku, Tokyo 107, Japan

Received 1 November 1996; accepted 26 September 1997

Abstract

The feasibility of a new structural system for nuclear power plant buildings utilizing concrete filled steel structures,termed ‘SC structural system’ was studied. SC wall test specimens (1/5 scale) were manufactured and compressiveloading tests were carried out to determine how to prevent buckling. Also, bending shear tests were performed usingH-section wall specimens to determine the shear and bending characteristics of SC walls. This paper presents anoutline of the feasibility study, and the various structural properties resulting from the experiments. © 1998 ElsevierScience S.A. All rights reserved.

1. Introduction

There have been several studies on SC structure(Fukumoto et al., 1987; Kaneuji et al., 1989;Kobayashi et al., 1985; Sekimoto et al., 1989), aswell as primary experiments. There are twobenefits from the application of SC. Firstly, SCenables the building to maintain a highly seismiccondition and secondly, due to SC’s prefabrica-tion, the buildings can be efficiently constructed.

However, SC is expensive compared with con-ventional reinforced concrete structures (RC), andit also has the disadvantage of requiring weldingwork at every joint of the SC panels. These disad-vantages can be redressed by using the thinnestpossible steel plates (around 6 mm) and employ-ing steel bars at the joints.

We developed, in detail, the building structuralsystem with SC (Fig. 1) based on the above

mentioned criteria, and carried out a feasibilitystudy on the construction of ABWR buildingsusing ‘SC’. Additionally, various experiments con-cerning structural property, and the constructionworkability were conducted in order to confirmthe viability of the ‘SC’ application.

Fig. 1. Overview of SC structural system.* Corresponding author. Tel.: +81 3 5561 2111; fax: +81

3 5561 2345.

0029-5493/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.

PII S0029 -5493 (97 )00282 -3

M. Takeuchi et al. / Nuclear Engineering and Design 179 (1998) 209–223210

Fig. 2. SC wall panel.

Fig. 4. Pipe support.

When laying pipe work along the walls, thesupports can be welded to any preferred positionon the surface plates, and the headed studs at-tached to the steel plates also serve as their anchorbolts (Fig. 4).

2.2. SC floors

For floors, a steel plate is attached to thebottom side, and a reinforcement mesh is placedat the top (Fig. 5). The reason for employing steelmesh is that a flexible surface finish is possible,and anchoring can be easily placed on to thesurrounding walls and girders (Fig. 6). Steel ribsare attached to the bottom plate, maintaining theshape of the panel during the erection and place-ment of the concrete. These ribs can also beutilized to enable the prefabrication of the pipework which is attached to the bottom plate.

2.3. SC columns, beams

Columns and beams need to be rigid members,as they support heavy vibrating machinery. Theyconsist of a concrete filled box-like steel casing(Fig. 7).

2. SC structural system

The walls, floors, columns and girders are allcomposed of concrete and steel plates with headedstuds. Head studs, being components that arehighly workable, prevent thin steel plates fromsectional buckling. It is possible to flexibly designthe diameters and pitches, in order to connect theplates and the concrete under various loadingconditions.

2.1. SC wall members

The steel wall panel shown in Fig. 2 is factoryproduced. Two plates are connected to form asandwich by means of tie-bars, and thus the shapeis easily maintained during transportation. Defor-mation, caused by the pressure of the concretewhen it is poured after erection is also prevented.The normal pitch of studs is approximately 20 cm.

Only when employed as shear walls, are thesepanels welded to each other, and assembled in thespecified shape for resisting seismic forces. Whenemployed as partition walls, the simple jointingtechnique with steel bars is used to fasten the steelplates to the ceiling and floor (Fig. 3).

Fig. 5. SC floor.Fig. 3. Wall joint.

M. Takeuchi et al. / Nuclear Engineering and Design 179 (1998) 209–223 211

Fig. 6. Wall–floor joint.

estimation of the quantity of construction mate-rial showed that a decrease in the amount of steel(around 20%) is possible; additional forms alsobecome unnecessary (Fig. 9). The constructioncost would therefore be about the same as for RCbuildings.

The total number of construction workers inthe field would also decrease by around 30% (Fig.10). Furthermore, because the ‘SC structural sys-tem’ requires only the relatively simple work ofassembling panels, filling the concrete and straightwelding, it is well suited for mechanized construc-tion. Thanks to prefabrication, the constructionperiod is 2–5 months shorter than current RCbuildings.

4. The structural properties tests

In the SC structural system, by the effective useof headed studs to prevent buckling, the thicknessof the steel plates can be reduced. A compressionloading test was conducted to confirm at whatpitch the headed studs should be welded at formaximum economy.

Additionally, there are the following questionsabout ‘SC’ bearing walls:1. The relationship between stress and displace-

ment.2. The failure mechanism and evaluation

method. Accordingly, a shear and bendingloading test, with a ‘H’ shaped cross-sectionSC wall specimens, was carried out.

4.1. Compression loading test

4.1.1. Test outlineThe test specimens were 1/5 scale models of

actual SC walls. As shown in Fig. 11. a total offour specimens were tested. The test parameterswere the width-thickness ratio (B/t), and fourvalues, 20, 30, 40 and 50, which were set toachieve plastic, inelastic and elastic buckling. Thethickness (t) of the surface steel plates in actualstructures is 6�16 mm. The thickness for each ofthe test specimens was 3.2 mm to ensure consis-tency. The design stud diameter to plate thicknessratio f/t was 1.4�2.2, and a stud diameter of 5

2.4. Construction procedure

When constructing the ‘SC structural system’,light SC panels of :3 tons produced in thefactory are erected in the order, columns, girders,walls and finally the floor (Fig. 8). After settingthe steel bars on the floor, concrete can be placedwithout formwork. Lastly, the joints between pan-els are welded or sealed.

Since the construction period of the SC systemis shorter, the subsequent interior machinery workcan be completed in 2–3 months earlier thancurrent RC buildings for nuclear power plants.

3. Feasibility study

A feasibility study was carried out to investi-gate the construction period, material quantitiesand construction costs, as well as the manpowerrequirements involved when an ABWR plant isconstructed using the ‘SC structural system’.

The rough design of the ‘SC’ using thin plateswas drafted, based on the results of structuralexperiments, which will be mentioned later. An

Fig. 7. Column and girder.


Fig. 8. Construction procedure.

mm (f/t=1.56) was chosen for the specimens.Concrete in an actual structure has a compressivestrength of 24�33 MPa, but for the specimen,ordinary concrete with a compressive strength of33 MPa was chosen. The size of the specimen wasdetermined to produce a clear buckling failure ofthe steel surface plate, with the width and heightthree times the stud spacing. The 10 MN com-pressive test machine used is shown in Fig. 12(details are reported in Takeuchi et al., 1995)

4.1.2. Outline of test resultsThe results of the test are summarized in Table

1. Fig. 14 shows the buckling wave of the surfaceplate. The following observations can be made:1. The observed buckling stresses (Section 4.1.5

below) increase with decreasing B/t ratios.2. The ultimate compressive load and the overall

compressive strains at the ultimate loads de-crease with increasing B/t ratios. The observed

compressive strains at ultimate load are about0.0033 times greater than the value of 0.0022obtained from the concrete material tests, dueto the confining effects of the steel plates.

3. The failure of the inner concrete initiated fromthe region where the surface steel plate buck-led. In addition, the range of failure was 1–2times the stud spacing B(0.5–1 times the wallthickness).

4.1.3. Load displacement relationshipThe observed relationships between the applied

load P and displacement d are shown in Fig. 13.The load–displacement relationship can be calcu-lated from the stress–strain relationship of thesteel plates and concrete. From these figures, thefollowing observations can be made:1. There was no sudden change in the load–dis-

placement relationships due to buckling oryielding of the steel plate.

2. The stiffness under loads of up to 3 MN wasunaffected by B/t. However, for loads over 3

Fig. 9. Material quantity. Fig. 10. Manpower requirement.


Tab

le1

Tes

tre

sult

san

dca

lcul

ated

valu

es

Cal

cula

ted

Spec

imen

B/t

rati

oE

xper

imen

tal

mar

k

cK(M

N/c

m)

esc r

(MP

a)eK

(MN

/cm

)cs

c r(M

Pa)

esc r

csc r

Fro

nt

Bac

keo

c r(×

10−

6)

cPm

ax

(MN

)eP

ma

x

ePm

ax

cPm

ax

eK cK(M

N)

×F

ront

Bac

k×

Fro

nt

Bac

k

62.1

0.88

287

54.4

20N

S20

1.07

5.73

5.33

284

—

0.99 —

2944 —

NS3

062

.149

.028

71.

1530

0.79

0.74 —

5.47

4.76

212

—16

32 —62

.10.

8522

052

.740

1.05

NS4

01.

01

1.02

4.76

5.00

222

225

1285

1217

62.1

0.78

141

48.1

501.

06N

S50

134

186

0.95

1.32

5.05

4.76

943

945

eK,

cK,

expe

rim

enta

lan

dca

lcul

ated

init

ial

stif

fnes

s;es

c r,

csc r

,ex

peri

men

tal

and

calc

ulat

edbu

cklin

gst

ress

;F

ront

,fr

ont

surf

ace

plat

e;B

ack,

back

surf

ace

plat

e;eo

c r,

coc r

,ex

peri

men

tal

and

calc

ulat

edbu

cklin

gax

ial

stra

in;

ePm

ax,

cPm

ax,

expe

rim

enta

lan

dca

lcul

ated

ulti

mat

elo

ad;

cPm

ax=

Fc·A

c+ss

y1

·As 1

+ss

y2

·As 2

.F

c,co

mpr

essi

vest

reng

thof

conc

rete

;A

c,A

s1,

As2

,se

ctio

nal

area

ofco

ncre

te,

side

plat

ean

dsu

rfac

e.E

c,E

s,Y

oung

’sm

odul

usof

conc

rete

and

stee

l;A

c,A

s,se

ctio

nal

area

ofco

ncre

tean

dst

eel,

csc r

=p

2·

Es/

12·

h2(B

/t)2

.h=

0.07

;B

,sp

acin

gin

terv

alof

head

edst

udbo

lt;

t,th

ickn

ess

ofsu

rfac

epl

ate;

ssy

1,

ssy

2,

yiel

dst

reng

thof

side

plat

ean

dsu

rfac

epl

ate.


Fig. 11. Dimension of test specimens.

gests that an increase in displacement due to acollapse of the concrete between the studs andsteel plate occurred in the tests (See Fig. 14).

4.1.4. Initial stiffness and ultimate loadAs shown in Table 1, the initial stiffness eK of

the test specimens obtained from test results are78–88% of the calculated stiffness cK. The sametendency was observed in our previous tests refer-ence Usami et al., 1991. The calculated ultimateloads cPmax, shown in Table 1, were obtainedunder the assumption that the steel plates cannotbear any compressive load after buckling. Themeasured ultimate load ePmax closely coincidewith the calculated values, with the exception ofspecimen NS30.

4.1.5. Buckling of surface steel platesTo accurately determine the buckling stress,

wire strain gages were attached to the outside andinside surface of the steel plates. The relationshipbetween the applied load and the strains in thesteel plate in the buckled region is shown in Fig.15. Strains both outside and inside the surface ofthe steel plate increase similarly before buckling.However, after buckling, they separate suddenlyand the outside strain tends to become tensile andthe inside strain tends to become more compres-sive. The buckling stress of the steel plates isevaluated by the following data analysis. First,the steel plate is divided into n transverse layersand the strain distribution is assumed to be linearin the transverse direction. Next, the stress in eachlayer is determined from the stress–strain rela-tionship of the steel, by assuming a strain value ineach layer. Finally, the average stress in the steelplate is evaluated as the cumulative mean stressesin the n layers. The relationship between averagestress and applied load is shown in Fig. 15. Asshown, the average compressive stress increasesinitially, but suddenly becomes more tensile afterbuckling. We define this turning point as thebuckling stress of the steel plate. The bucklingstresses and strains are summarized in Table 1.Figs. 16 and 17 show the relationship between thewidth–thickness ratio and the buckling stress andstrain, respectively.

MN, the greater the value of B/t, the smaller thestiffness. This tendency is considered to resultfrom the confining effects of the concrete.3. The calculated P–d relationship can simulatecorrectly the observed relationship for loads in therange 0.5–3.5 MN. However, for a greater loadlevel, some discrepancies were observed. This sug-

Fig. 12. Loading method.


Fig. 13. Relation of load versus displacement.

From these results, the buckling stress can beevaluated using Euler’s equation for elastic buck-ling of columns, using B/t as the slenderness ratio.

4.2. Shear and bending loading test

4.2.1. Test outline(1) Specimens. Factors affecting the bending

shear characteristics of SC structures are shearspan ratio (height H/length L), steel ratio and theexistence of axial stress. In addition, whether ornot stud bolts are incorporated in the region ofthe joint between the web wall and flange wall isan important factor affecting cost effectivenessand ease of construction. These factors were ex-amined as test parameters using a total of seventest specimens. The specimens are listed in Table2. Their cross sections were equivalent to about

1/3–1/2 that of a full scale wall. As it was difficultto obtain steel plates of differing thicknesses andhaving the same mechanical properties, the steelratio was altered by changing the wall thickness.To obtain the shear strength of the SC structure,bending reinforcing plates were attached at theedge regions of the flange walls, so that shearfailure would occur after bending yield of theflange steel plate, but prior to bending failure. Theconfiguration and dimensions of the test speci-mens are shown in Fig. 18. Width-to-thicknessratio (stud bolt pitch/plate thickness) of the sur-face steel plates was chosen based on the compres-sion test results, to prevent elastic buckling of thesteel plates. A value of 33 was chosen for allspecimens, the resulting stud bolt pitch being 76mm (details are reported in Takeuchi et al., 1995).

(2) Test method. The test specimen mat slabwas fixed to the test bed using PC steel bars,and repetitive positive and negative horizontalloads were applied via the loading slab. Equaltensile and compressive loads were applied to theleft and right loading slabs by hydraulic jacks.The testing apparatus is shown in Fig. 19. Theabsolute and relative displacements were mea-sured by LVDTs. Absolute displacements weremeasured against measuring frames, supportedat four points on the mat skab. The strains inthe steel plate and the concrete were measuredby wire strain gauges. Strain gauges were alsoattached in three directions to the mainFig. 14. Buckling wave of surface plate.


Fig. 15. Relation of load versus buckling strain and axial stress.

parts, such as the web steel plate, to enable calcu-lation of principle strain and shear strain.

4.2.2. Outline of test results(1) Obser6ations. All test specimens demon-

strated the same failure pattern, i.e. sounds ofconcrete cracking occurred, and the steel plates

yielded, then buckled, and finally reached maxi-mum load. After this, depending on the level ofdamage to the specimen, a further load was ap-plied until a rotation angle of 1/40�1/25 wasreached. In some specimens, cracking occurred atthe foot of the flange plate on the bending tensionside, close to the maximum load. At ultimatedeformation, the crack increased in size with aloud noise and a certain reduction of strengthoccurred. The specimen H15T10 after loading isshown in Fig. 20 (Every two sections—intersec-tion of the straight lines—indicates stud bolt po-sitions in the left photograph). The condition ofthe internal concrete of specimen H10T05 afterthe surface steel plates were removed can be seenin Fig. 21. The following results were obtainedfrom all specimens:

Fig. 16. Relation of buckling stress versus width–thicknessratio.

Fig. 17. Relation of buckling strain versus width–thicknessratio.

Table 2Summary of specimen

Steel ratio Shear–span ratio

1.531.090.87h=166 cm h=250 cmh=125

cm

H10T05T=11.54.00%cm

H10T10T=23.0 H15T102.00% H07T10 H10T10Na1cm

H10T10Vb2T=34.51.33% H10T15cm

a No. stud bolts at the connection.b Axial stress of 3 MPa is applied.


Fig. 18. Test specimen.

1. Buckling occurred in the region between studbolt rows in the web plate at an angle of 45°,and also in the lower portion of the flangeplate in the horizontal direction (Fig. 20).

2. All steel plate buckling occurred after yielding(Table 3)

3. Prominent cracks ran between stud bolts at anapproximate angle of 45°, to the horizontal inthe web concrete, and also horizontally alongthe flange concrete (Fig. 21).

4.2.3. Shear stress and displacementThe relationship between the shear stress occur-

ring under positive loading and the rotation angleat the top of the wall, are shown as envelope linesdrawn for each parameter in Figs. 22–24. Theshear stress is obtained by dividing the appliedload by the effective cross sectional area shown in

the same figure. The rotation angle is obtainedfrom the absolute horizontal deformation at thetop of the wall measured by the LDVT, less theoutcropping deformation at the foot of the wall,divided by the internal height. From these figures,the following results were obtained:1. All test specimens were brought to the maxi-

mum load condition without sudden loaddrops or spillage, and a satisfactory stableload deformation relation was achieved (seeFigs. 22 and 23).

2. After the maximum load was exceeded, allspecimens exhibited good ductility, keeping70�80% of the maximum load, althoughcracks occurred in the flange plates of somespecimens (see Figs. 22 and 23).

3. Test specimens stiffness and strength increasedwith decreasing shear span ratio and increas-ing steel ratio (see Figs. 22 and 23).

4. Axial stress had little effect on stiffness, butthe ultimate strength increased (see Fig. 24).

5. The stud bolts in the web to flange joint regionhave no effect on the relationship betweenshear stress and rotation angle (see Fig. 24).

In terms of ductility and ultimate strength, the SCstructure performs better than an equivalent RCstructure.

4.2.4. Strain distributionThe principal strain distribution and the shear

strain distribution in the web steel plate at theyield load level are shown in Fig. 25, respectively.Similar results were obtained for the other testFig. 19. Testing apparatus.


Fig. 20. Specimen after loading (H15T10).

Fig. 21. Concrete surface after loading (H10T05).

specimens. From these figures, the following re-sults were obtained:1. The applied load was distributed fairly uniformly

over the entire surface of the web steel plate (seeFig. 25).

2. Regardless of the shear span ratio, with theexception in the region of the foot, where bendingmoments are dominant, the direction of theprincipal strain acted at an angle of 45° to thehorizontal (see Fig. 25).

3. The shear stress was sustained fairly uniformlyover the entire surface of the web steel plate.

4. Attheinnerwebportion,theverticalstrainvariedlinearly,whileattheflangeportion,a largerstraincan be seen acting in the vertical direction. Thisis thought to be the effect of partial bendingmoment acting on the flange walls.

4.2.5. Analytical model(1) As the results of the tests show, we consid-

ered three types for each loading level as shown inFig. 26, in order to assess the bearing mechanismof SC walls.At lower loading levels, SC walls arecomposed of the elastic steel surface plates andinner concrete. Therefore, the relationship be-tween the shear stress Q1 and the rotation angle g1

is given in Eq. (1).

Q1= (As · Gs+Ac · Gc) · g1 (1)

where Gs,c is the shear modulus of steel plate andconcrete; and As,c is the cross section area of steeland concrete.

(2) After increasing the load level, many cracksoccurred in the inner concrete which cannot sup-


Table 3Summary of test results

Stress (MPa) Initial stiffness Flange plate(×10 MN cm−1) tensile failurea

MaximumWeb plateFlange plate

BucklingYield Buckling Yield

A 10.6 2.57 AH07T10 6.5 7.9 6.5B0.8512.6H10T05 12.57.1 8.8 10.1

9.5 3.09H10T15 5.6 8.1 5.0 A AB2.159.3H10T10V 7.45.1 8.4 6.1

8.5 9.4 2.21 BH10T10 5.7 7.2 6.00.73 N9.5H10T10N 8.18.2 9.0 5.3

9.5 0.73H15T10 6.7 8.5 5.3 N8.1

a N, non occurrence; B, occurence before max load; A, occurence after max load.

port the diagonal tensile force. The concretechanges its properties to exhibit anisotropic elas-ticity as in the following stiffness metrics [c].

[c]=Ac · Ec · [T1]−1 · ÃÆ

È

000

010

000ÃÇ

É· [T2]

=Ac · Ec · ÃÆ

È

sin4 u

sin2 u cos2 u

−sin3 u cos u

sin2 u cos2 u

cos4 u

−sin u cos3 u

−sin3 u cos u

−sin u cos3 u

sin2 u cos2 u

ÃÇ

É(2)

where [T1] is the stress transformation martix; [T2]is the strain transformation matrix; and u is thestrut’s angle at the web concrete.

Here, the concretes stiffness Ec is decreased to0.7 oEc (oEc: Youngs modulus obtained by thecylinder test) caused by cracking.

The steel plates stiffness is expressed as follows:

Fig. 22. Shear stress-rotation angle for various shear-spanratios. Fig. 23. Shear stress-rotation angle for various steel ratios.


Fig. 24. Shear stress-rotation angle for other parameters.

4.2.6. E6aluation method(1) Shear stress. Based on the former model,

the typical loads representing the properties of SCwalls under shear stress (i.e. cracking, yielding,maximum), are calculated in the following equa-tion.

(1) The cracking load is given as follows, ac-cording to Eq. (1):

Qcr= (Ac+Gs/Gc · As) · tcr

gcr=tcr

/Gc

Here, tcr=sB shear cracking strength

(2) The yielding load based on the theory ofVon Mises is given, as follows, according to Eqs.(2)–(4).

Qy= (a+b)/3a2+ (As/Ac)2 · b2 · As · sy

gy=Qy/(a+b)

Here,a=As ·Gs: shear stiffness of steel plate; b=1/{4/(Ac ·Ec)+2(1-ns)/As ·Es}: shear stiffness ofinner concrete.

(3) The maximum load is given in the followingequation, where only the truss mechanism exists.(sw=sy, cot2 f= (n ·sB)/Pw ·sy), in Eq. (5). Theultimate rotation angles obtained from the experi-mental results of shear deformation are almost aconstant value 6.0×10-3 rad.

Qu=Ac · As/Ac · sy · n · sB

gu=6.0×10−3 (rad)

[s]=As · Es

1−ns2 · ÃÆ

È

1ns0

ns10

00

(1−ns)/2ÃÇ

É(3)

The relationship between the supported shearstress Q2 and the rotation angle g2 is shown in Eq.(4):

ÍÁ

Ä

NxNyQ2

ÌÂ

Å= [[c]+ [s]] · Í

Á

Ä

oxoyg2

ÌÂ

Å, Nx=Ny=0 (4)

(3) In the ultimate state, the surface plates alsobecame anisotrophic due to buckling. An analyti-cal model of resistance with the plates and con-crete assumes that a truss and arch mechanism arecoexisting as shown in Fig. 27.

The maximum strength can be obtained in Eq.(5), this model being based on the lower boundtheory of limit analysis (details are reported inSuzuki et al., 1995)

Q3=Ac · Pw · sw · cot f (truss mechanism)+Ac · (1−bc) · n · sB/2 · cot uc (concrete arch mechanism)

+Ac · (1−bs) · Pw · sy/2 · cot us (steel arch mechanism) (5)

Here,

bc= Pw ·sw · cot2f/(n ·sB)bs= Pw ·sw/(Pw ·sy)Pw= As/Ac

0.7-sB/2000: coefficient of effective concrete strengthn=sB: cylinder strength of concretesy: yield strength of steel platesw: supported stress of steel plate in the truss mechanism


Fig. 25. Principle strain distribution in the Web plate.

Fig. 26. Mechanism for shear loading.

(2) O6erturning moment. The bearing mecha-nism concerning the overturning moment of an SCwall is similar to that of conventional RC wall. Thesteel plates are evaluated in the same way as thereinforcing bars. The representative evaluationmethod is shown in JEAG4601, 1991

4.2.7. ApplicationThe evaluation method was applied to every test

specimen. The experimental and calculated curvesof relationships between horizontal and rotationangles are shown in Fig. 28. The calculated rotation

angles are determined to sum up the deformationscalculated by the shear stress and the overturningmoment at each point. Comparing the two curves,the calculated relationship between the load and thedeformation predicted the experimental result suc-cessfully. The calculated values of yielding load aregreater than the test results observed with the wirestrain gauges (attached to the surface plates),although the tangential gradient of the test curvesdecrease near the calculated points.

5. Mock-up test

5.1. Objecti6es

One of the objectives was to examine possibleshortcomings, relating to manufacturing and con-struction. A lot of thin steel plates are used in the‘SC structural system’. Some of the problemsconsidered were,Fig. 27. Truss and arch mechanism.


Fig. 28. Comparison of experimental and calculated relationship between load and deformation.

1. The formation of surface ripples caused bywelding heat.

2. The perforation of the steel plates caused bythe headed studs during manufacturing.

3. The degree of out-of-plane deformation whenthe steel case is filled with concrete.

Another objective was to evaluate workabil-ity—ease of erection of such panels and fillingwith concrete, as well as the quality of the finishedproduct. In order to study these objectives, a fullscale model of height 4 m (1/2 scale) span 8×5 mwas built.

5.2. Outline of test results

An overview of the experiment is given in Fig.29. The components indicated in Figs. 2–7 wereused. Figs. 30 and 31 show the completed walland floor.

Almost no surface ripples occurred, and theprecision of the measurement was 92 mm.

The panels were erected rapidly using a 4 toncrane. The panels, assembled in sandwich form,experienced very little flexing. Ordinary concretewas used with a slump of 12 cm for the floor and


Fig. 29. Outward appearance.

Fig. 31. Floor panel.

� The buckling and yielding phenomena of steelplates have no influence on the overall loaddisplacement relationship of SC walls

� The buckling stress can be evaluated usingEuler’s equation for elastic buckling ofcolumns with one fixed end and one pin-jointedend.(3) From the shear and bending tests, we can

conclude.� The SC structure has a superior seismic capa-

bility than the equivalent RC structures.� Some evaluation, yielding and ultimate stress

and deformation have been developed.In the near future, durability and fire-proofing

must be assessed, as they are considered impor-tant themes for future studies.

References

Fukumoto, H., Kobayashi, M., et al., 1987. Concrete filledbearing walls. IABSE, vol. 5, pp. 467–472.

JEAG4601, 1991. Technical guidelines for aseismic design ofnuclear power plants (Suppl.), pp. 79–92.

Kaneuji, A., Hara, K., et al., 1989. Feasibility study of filled steel(SC), structure for reactor building, Tenth SMiRT Confer-ence, pp. 67–72.

Kobayasi, M., Sakamoto, M., et al., 1985. Experimental studyof concrete filled steel bearing walls (Part 2 compressiontest), Proceedings Annual meeting of Arch. Inst. Japan, pp.1325–1326.

Sekimoto, H. Akiyama, H., et al., 1989. 1/10th scale model testof inner concrete structure composed of concrete filled steelbearing wall. Tenth SMiRT Conference H73, pp. 73–78.

Suzuki, N., Narikawa, M., et al., 1995. Study on a concrete filledsteel structure for nuclear power plants (Part 4), 13th SMiRTConference, pp. 33–38.

Takeuchi, M., Matsuo, I., et al., 1995. Study on a concrete steelfilled structure for nuclear power plants (Part 1–3), 13thSMiRT Conference, pp. 15–32.

Usami, S., Sekimoto, H., et al., 1991. Compression and shearloading test of concrete filled steel bearing wall, 11th SMiRTConference, H12/2, pp. 323–328.

Fig. 30. Wall panel.

15 cm for the walls. The out-plane deformations ofthe surface plates were measured and came to only2–4 mm. Because there were only a few obstructionswithin the panels, the concrete was positionedsatisfactorily without air pockets. Since the pipework supports can be welded to any position on thesurface plates, the equipment pipe work that willbe carried out after construction should also proveto be efficient.

6. Conclusions

(1) The SC structural system for nuclear powerplants was proposed. From the feasibility study, wecan conclude that,� The construction costs would be approximately

the same as RC buildings.� The construction period can be greatly re-

duced.� The total number of construction workers

needed in the field would also decrease.� It also faciltates efficient building construction.

(2) The following conclusions were obtainedfrom the compression loading test results.

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Study on a concrete filled structure for nuclear power plants