定軸力のもとで繰返しせん断力を受けるコンクリート充てん角形鋼管短柱に関する実験的研究(梗概)

(1)

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EXPERIMENTAL

STUDIES

ON

CONCRETE

FILLED

SQUARE

STEEL

TUBULAR

SHORT

COLUMNS

SUBJECTED

TO

CYCLIC

SHEARING

FORCE

AND

CONSTANT

AXIAL

FORCE

by

KENJI

SAKINO'

and

HISAYOSHI

ISHIBASHI"

Members

of

A. I.J.

1. INTRODUCTION

Tubular

sections, either ernpty or

filled

with concrete, are

being

increasingly

used as structural rnembers,

When

a

tube

is

acting

as

a compression rnember,

filling

the

tube

with concrete

is

advantageotts

because

it

increases

the

load-carrying

capacity

without

increasing

_the

size of

_the

column.

The

senior

author

have

participated

in

the

following

investigations

on concrete

filled

square steel

tubular

col'umns

1 (1)

An

assessment of

the

state of

the

art and [esearch on concrete

filled

steeL

tube

structures]).

(

2 )

Elasto-plastic

behavior

of columns subjected

to

constant axial

foTce

and monotonic

bending

momenti)3).

(3)

Elasto-plastic

behavior

of

columns

subjected

to

constant

axial

force

and

monotonic shearing

force

(see

Fig.

04).

(

4 )

Ultimate

shear strength

of

plain

concrete

columns,

which are

the

component

of

the

concrete

filled

steel

tubular

columns,

subjected

to

constant

axial

force

and

monotonic

N

shearing

force

S},

(5)

Hysteretic

behavior

of columns

failed

in

flexureM.

In

the

paper`),

it

was clarified

that

columns with shear span

to

depth

ratios

(alD)

equal

to

or

_greater

than

2 failed

in

fLexure

but

columns with shear span

to

depth

ratios equal

to

or

less

than1

failed

in

shear.

In

this

_paper,

an experimental work

to

study

the

following

_problems

is

described

at

first.

{1>

Failure

mode of

the

columns with

alD=:1.5.

(2)

Hysteretic

behavior

of short columns

failing

in

shear.

And

an analytical method

to

estimate

the

ultimate strength of short columns

is

discussed

]ater.

It

is

of

importance

te

investigate

the

mechanical

b

for

_practical

reasons.

Short

columns commonly appea[

in

deep

spandrel

beams

and such cotumns.

Even

in

f[ame

systems,

the

columns may

be

restraints

introduced

by

nonstructural elements.

2,

EXPERIMENTAL

PROGRAM

Test

specimens-The

range

of

the

variables

in

the

test

_program

was as

follows:(1)

afP,

which

was

1.

5 for

monotenic

lea

were

tested

under monotonic

loading

by

the

senior author

_{previously"].}

{2)

wall wiclth

to

wall

thickness

ratio,

_Dlt:45,

34

and

_24;(3)

and

IV6

is

the

nominal axial

force

capacity):between

O

and

o.s.

The

test

program,

which

included

21

specimens, was

divided

into

6

series

(see

Table

1).

M

R

Q

a

K

%.R.ll

N

Fig.1

Loading

conditien

'

ehavior of short columns not only

for

academic

_purposes

but

also

spandrel wall-frame systems which are characterized

by

rendered short

due

to

Lhe

Shear

span

to

depth

ratio,

ding

and

1 for

cyclic

loading

(Columns

with

alD

ratios equal

to

or

less

than

1 Those

results are also utilized

in

this

_paper);

NINo

ratio

(N

is

the

constant axial

force

applied,

The

vaiiable

_parameters

'

_Associate

_Professor,

_Depaitment

_of

_{Architecture,}

Faculty

_of

_Engineering,

Kyushu

_University,

_Dr.

_Eng.

"

_Kumagai

_Gumi

_Company

_LTD,,

_M.

_Eng.

(2)

-81-NII-Electronic Library Service

Table1

Properties

of speclmens and test resu]ts DEIo

H

nlo

kr!2t

"

u pt

p

h

E

: a

{

q

b

h

E

"8

g=i.5

g;i

Menotonic

Loading

Cyc]ic

Leeding Note: al] = shear span rat ±o. t

=

thickness of wall.

D]breadth

and depth of steel tube. st[Jy=yield point stre5S･ AIIDimensiens incm

ou ! tensile strength.

Fer

=

eempress ±ve strength of expansive

cencrete cylindei cured tn the mould.

No

= _sA_{sgy +}_cA

d]B.

Fig.2

Details

of

the

test

specimens and

the

CaOsis.=.eedOMtPorebSeSl"iFSet,r-et"gQtuh

.ef.ietniCmaaSteed

$ChOenaCrrientgefaonrdceh,aS

been

_location

_of _strain

_gauges

Table2

Mix

proportions

ofconcrete

_between

_the

_{series were}

_the

Dlt

ratio

and

the

a7D

ratio, and

the

variable

_parameter

between

the

specimens

in

each

series

was

the

NIN,

ratio.

All

specimens

were

₁₀

em

by

10 cm

in

cross

sections.

The

external

dimensions

of

the

specimens are

shown

in

Fig.2.

Materials-The

concrete mix

_proportions

are shown

in

Table

2. Expansive

cement containing

15 _percent

of expansive cemponent was used

in

order

to

_p[event

separation at

the

interface

of

the

encased concrete and

the

steel

tube

due

to

shrinkage of

the

concrete.

Tubes

were cotd worked welded mild steel, and all

tubes

were annealed

to

remove Tesidual stresses

in

their

cross sections.

Mechanical

_properties

obtained

from

coupon

tests

are

shown

in

Table

].

Experimental

apparatus

and

procedure-A

test

set-up

is

shown

in

Fig,

3. The

loacling

apparatus

was

designed

to

reproduce

the

basie

force-deformation

_pattern

of

columns

shown

in

Fig.

].

Details

Qf

the

loading

apparatus

and

'

J

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loading

is

shown

in

Fig.4.

3. EXPERIMENTAL

RESULTS

-1

'i

Q-translation

angle

R

Telationships are shown

in

Fig.s.

Initiatien

points

of visually ob$eTved

local

buckling

and

yielding

of

the

steel

tube

Fig.4

Loading

program

are also

ifidicated

in

the

figure.

Crack

_pattems

of

the

encased concrete were observed

by

cutting and removing

the

half

of

the

steel

tube.

The

typical

crack

_patterns

of coiumns with alD ratios

of1

and

l.s

are compared

in

Fig.

_6.

The

diagonal

cracking

observed

in

the

shorter columns

is

not

bbserved

in

the

case

of

the

more slender col.umns,

in

which

_plastic

hinges

are

developed

at

its

ends

;

the

failure

mode of

the

columns with

_alDt=1.s

is

considered

te

be

flexural

failure.

Coiumns

with

a!D=1

(cyclic

loading)-The

shearing

force-translation

angle relationships are shown

in

Fig.

7. As

shewn

in

this

figure,

a considerable

amount

of

energy ab$orption

is

avai!able

in

any of

these

cases.

For

high

axial

loads

_(NIN,#O.5),

hysteretic

loops

becarne

stable only after a certain amount

of

the

degradation

in

the

shear resistance

took

_place.

However,

an

increase

in

the

shear resistance,

due

to

cyclic

loading

at

large

displacement

levels,

was ob$erved..The reason

for

this

phenomenon

is

that

the

square

.section

gradual-ly

became

a circular section

in

the

upper and

lower

critical regions

(see

Fig,6

c)

due

to

the

N

v

I

gal

:;S=O.6PIain

Conciete Cotumn S] Ce}Fig.6

Typical

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(a!D=1.

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(4)

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Shearing

ferce

Q-t[anslation

angle

R

relationships

local

buckling

of

the

flanges

and webs, and

this

t[ansformed

ciicular steel

tube

contained

the

encased concrete rnore effectively

than

the

square steel

tube,

To

investigate

the

effect of shear span

to

depth

ratio on

the

hystereti'c

behavior

of

the

columns,

the

relationships

between

the

non-dimensional shearing

force

at

the

un]oading

_points

and

the

corresponding

translation

angtes

are shown

in

Fig.

8 for

the

columns with

Dlt=45

in

which

the

degradation

of

the

shear resistance

due

to

cyclic

loading

was most

_prominent,

The

failure

mode of

the

co!umns with

alD=1

was considered as sheaT

failure

as

described

later,

and

that

of

the

columns with

alD=:[2

and

₃

as

flexural

failure6i.

As

shown

in

Fig.

_8,

the

cyclic

deterioration

of

the

columns

failing

in

shear was

less

than

that

of

the

columns

failing

in

flexure.

This

noticeable resultwas consistent

in

the

columns with

Dlt==34

and

24.

4. ULTIMATE

STRENGTH

OF

THE

SHORT

COLUMNS

The

concrete

fMed

steel

tubutar

column

is

a composite member

cornprised

of

the

steel and

the

concrete').

M. Wakabayashi

and

K,

Minami

have

_preposed

an analytical method

to

estimate

the

ultimate

strength

of

sueh

composite

members.

This

method, which was considered

to

be

extension of an analyticat method

_proposed

by

B,

Kato

and

R. Shohara

for

concrete

encased

steel

coluTnns9),

was

proved

to

be

applicable

to

many

type$

of composite members

(5)

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Nondimensiona[

shearing

force

at unioadlng

_point

QIQu-translatien

ang[e

R

relationshlps

_Dlt=45

(Comparison

between

the columns

failing

in

shear

(a!D

=

1)

and the columns

failing

in

flexure

(alD=2

anfl

3)S])

sNsM-t't'Xso1ebrb1111'J1 rljldd11SHsPDAsQ<I:J}-sM

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Assumed

stress

distributions

in

steet tube

f[anges

and

webs

(by

TanakaiO))

force

and a more sirnplified admissibie stress

field

is

assumed.

be

shown

in

the

numerical examples

_presented

for

comparing

the

analytical and experimental results.

the

"lower

bound

theorem"

of

the

limit

analysis,

Eq.1

and strength of

the

steel

tubular

column on condition

that

the

_plastic

de

Ultimate

strength

of

the

encased

concrete

column-Accord

Kato,

the

ultimate strength

expressed

in

the

non-dimensiona

failing

in

shear of

flexure3).

According

to

this

method,

the

ultimate strength of

the

concrete

filted

$teel

tubular

columns can

be

obtained

by

adding

the

strengths of

the

steel

tubular

column

and

the

encased concrete column.

In

this

section, an

improved

rnethod will

be

_proposed.

Differences

among

three

methods

_proposed

by

B. Kato

'

et al,,

M. Wakabayashi

et al. and

the

authois, are

in:

<

l

>

Methods

to

estimate

the

ultimate strengths of

the

steel

tubular

column ancl

the

encased conc[ete

column.

(2)

Methods

to

add

these

strengths.

At

first,

methods

for

estimating

the

ultirnate strengths

of

the

steel

tubular

column and

the

encased concrete

column

are

described.

Ultimate

strength

ot

the

steel

tubular

column-The

ultirnate

strength of

the

steel

tubular

column under

the

loading

condition shown

in

Fig.1

is

_given

by

Eq.1,

which was obtained

by

a

limit

analysis

in

whieh

the

following

assumptions were rnade]O).

(])

The

shearing stress. .T.,

is

uniformly

buted

in

the

webs as shown

in

Fig.9.

(2)

Thenormalstresses.a.M,

and.a.N, causedby

bending

moment, _.M., and axial

force,

_.Ai.,

respectively, are uniformly

distributed

as shown

in

Fig.9.

(3)

The

yield

condition

is

_given

by

Eq.2.

sq =21s

(in

case of

2.n+4.i.qso

(3+4.di).qi+4.asn.q-2sE.q.-sn+sn!=O

(in

case of

2.n+4.a.q)1)4.Esq}

(3+16.Ei).qZ-8.d.q+sn!+-43-=O

{in

case of

4.a.q21)

･･･''''''''''''''''''''''''''(

]

)

where

sQu

a

sNsn==.N,,

sq!.lvh, sa=.D, sNo=4t(D-t).av .av=yield

point

stress of

the

steel

tube.

3srw2+sawM2+sawN2=sar･･････････････････････(2}

In

Wakabayashi's

methocl, almost same

equation

as

Eq.

1 is

used,

even

though

the

expression

is

clifferent,

In

Kato's

rnethod,

the

steel

tubular

column, whose _.a

is

larger

thah

O.

866 Dl.D,

is

assumed not

to

carry axia!

The

difference

between

Kato's

method and

Eq,

1

will

According

to

Kato's

method

_give

the

Lower

bound

for

the

ultimate

formation

capacity of

the

steel

tube

is

adequate.

ing

to

the

rnethodS

_proposed

by

Wakabayashi

and

1

shearing

force

term

of

the

encased concrete celumn

(6)

-85-NII-Electronic Library Service

i.o

g.l.o

cD

ARI

conciete cotumn assumed

in

Wedge

Theory

interaction cttrves

for

the

{by

Suenaga,

et al.M} encased concrete columns under

the

loading

condition shown

in

Fig,

1,

can

be

_given

by

Eq.

3

which

is

obtained

from

the

admissible stress

field

shown

in

Fig.

10

a.

According

to

the

"lower

bound

theorem",

Eq.

3 gives

the

lower

bound

for

the

encased concrete column,

On

the

other

hand,

Eq.

4 is

obtained

by

assuming

the

stress

block

shown

in

Fig,

10 b,

in

which

the

effect

of

the

shearing

force

is

ignoTed.

cq= cn(1-cn)+ca2-.d･･･--"---･･-･･･---･-･･･--･-･-･･･---･･---･･-･-･---･-{3)

cq=2,1-a cn(1-en)''-'"''"""-''-'""'"--'"''""'''"""H-"-''"HH"'-''"'"--"-""-'"'"'"'""v'"(

4 )

where

.IV .Q.

a

cn=71mv6, cq=cNo, cU=cD, cNo=cDl.aB

.aB=icompressiye strength of

the

encasecl concrete.

In

the

experiments on

the

_plain

concrete shoTt columns undeT

the

loading

condition shown

in

Fig.

1,

it

was reported

that

the

following

three

failure

modes were observed5),

(

1 )

shear

failure-Thediagonal

tension

crack extends

in

thedirection

of

aline

joining

both

compressive regions

of

column

ends

(see

Fig.

6 a).

Failure

occurs

simultaneously

with

the

formation

of

this

diagonal

tension

crack

(see

Fig,

6

a).

(

2 )

pest

flexura]

crack-shear

failure-The

diagonal

crack

_pattern

and

failure

mechanism of

this

failure

mode are

similar

to

those

of

the

shear

failure.

{3)

flexural

failure-The

large

horizontal

displacement

due

to

widening of

flexural

c[acks at

the

ends

occvrs

without

the

formation

of

the

diagonal

crack.

It

was also reported

that

the

diagonal

tension

cracking

load

is

larger

than

the

shearing

force

_given

by

Eq.

3

and can

be

given

by

Eq.5,

.q=SI(ci-2cacD+

4(2cdci+c2)cn-4cn2+<cT-2cEct)'1

(incaseofcn>2c]ca)

--･--･-･･-･----･(

5 )

lcn

cq--2,a

"n

CaSe Of cn<2cicE

･･-････-･flexural

failure)

where c,=O.1109, c!=O.7680

Eq.

s

was obtained

from

the

"Wedge

_Theory"

proposed

by

Suenaga

and

Ishimaruii),

in

which

the

failure

mechanism and

the

yield

condition

for

the

concrete shown

in

Fig.11

were assumed.

Fig.12

shows a

comparison

ameng

the

axial

load-shearing

force

interaction

curves

_given

by

Eqs.3,

4

and

s.

Experimenta!

results5) on

the

_plain

concrete short columns are also

_plotted

in

Fig.12.

(7)

Ultimate

strength

of

the

concrete

filled

steel

tubular

column-According

to

Kato's

method,

the

ultimate

strength

of

the

cencrete

filled

steel

tubular

column

is

estimated

by

the

"Simple

_Superposed

Strength

Method"

foi

the

columns whose

al.D

ratio

is

larger

than

O.

866

.DID, and

is

given

by

Eq.6.

N=!cN

Qu==sQtt+cQu-''h''-'"H''""-'""H"HHH""""H--'H-"'''-H"h-''"'''-H---"''"''(6)

where _cQ.

is

_given

by

Eq.

_3,

ancl subscripts

s

and

c

indicate

forces

ca[ried

by

the

steel

tubular

column and

the

encased concrete column, respectively.

Wakabayashi

et al.

_proposed

to

use

the

"Extended

Superposed

Strength

Method"iL'),

in

which

Eq.7

is

utilized.

N=sN+cN

Qu=sQu+cQu"1"'''--'''-"''"H-"'H''H'H--''"""H''"'''-"''"''H'H'''''-'''-(7)

Where

,Q.

is

given

by

Eq.

1

ancl ,Q.

is

given

by

Eq.

3. The

value of each

term

appearing

in

the

right

hand

side of

Eq,

7

shourd

be

taken

in

such away

that

the

absolute value of

the

yector

_given

by

IV

and

Q

becomes

maximum.

The

rnethod

_proposed

in

this

_paper

is

similar

to

Wakabayashi's

method except

that

Eq,

5 is

used

to

estimate

the

ultimate

strength

of

the

encased

concrete

cotumn

instead

of

Eq.3.

Comparison

between

analytical

and

experimental

results-Fig.

13

shows

_the

cornparison

between

analytical

and experimental results

for

columns with alD ratio$

equal

to

or

less

than

1.

5. The

experirnentar

results`)

for

columns

with

alDS1.

0

subjected

to

monotonic shearing

force

are also shown

in

Fig.

₁₃

a-j.

The

following

analytical resuits

are also

included

in

Fig.

₁₃

a-j.

{1)

UItimate

strengths

of

the

encased

concrete columns

_given

by

Eqs,3

and

_5.,

<2}

Ultimate

strength of

the

steel

tubular

columns

_given

by

Eq.1.

(

3 )

Ultimate

strengths

of

the

concrete

fiiled

steel

tubular

columns obtained

by

the

thiee

methods

_proposed

by

Kato,

Wakabayashi

and allthors.

(

4 )

Ultimate

strength ol

the

concrete

filled

steel

tubular

colttmns

_given

by

Q=M,.la,

where

M,.,

is

the

ultimate moment calculated

by

asimpte

_ptastic

theory

_propased

in

Ref.

_2,

in

which rectangular

stress

blocks

di

for

concrete and steel were assttmed.

This

ultimate strength

is

referred

to

as

the

flexural

strength

hereafter,

In

calculating

the

analytical strengths,

the

compressive strength, _cae, of

the

encasecl

concrete

has

been

taken

as

1.2 times

_of

the

_cornpressive _s!rength _{of expansive} _concrete _cylinder _cured

in

the

_mouldZM).

Following

conclusions can

be

drawn

from

Fig.

13

a-j.

'

(1)

The

lower

bound

of experimental results

is

estimated

by

the

analytical

niethods

_proposed

by

Kato

or

Wakabayashi

in

all cases.

(

2 )

To

estimate

the

ultimate strength

of

the

short column more accurately,

the

method

prop6sed

in

this

paper

can

be

used.

(

3 )

The

the

columns with

alD=1.

5,

'which

failed

in

flexure,

are

laTger

than

the

analytical

flexural

strength.

Detinition

of

shear

tailure-According

to

the

definition

_given

by

Kato

or

Wakabayashi,

the

failure

mode of a]1

the

columns

described

in

this

_paper

is

not

L`shear

failure"

but

"flexural

failure"

since

that

both

flanges

of

the

steel

tube

yielcled

at

the

ultimate state.

According

to

the

author's

delinition,

however,

the

failure

mode of all

the

columns

described

in

this

_paper

is

"shear

failure"

since

the

encased concrete

columns

failed

in

shear.

Obviously,

the

definition

of

"shear

faiLure"

is

debatable.

Limitations

of

the

_proposed

method-As

discussed

_previously,

in

case of

'columns

with alD=1.5, significant

diagonal

tension

cracking

of

the

encased

concrete was not

observed.

However,

the

failure

mechanism shown

in

Fig.

11

was assumed

in

order

to

obtain

Eq,

5,

According

to

the

"upper

_bound

theorem",

the

ultiTnate strength

of

the

encased concTete column

is

overestimated

by

Eq.5

for

the

co}umns with afD=:1.5.

Consequently,

the

application

of

the

proposed

method

shovld

have

limitations.

In

this

_paper,

following

limitations

are

proposed.

(1)

O.5galDSI.5

The

reasons

for

this

limitation

are as

fo]lows:

i)

Eq.5

was experimentally

_proved

only

for

this

range5).

ii

)

The

proposed

method

_gives

the

ultimate shear strength similar

to

the

flexural

strength

for

the

coLurnns itTith

(8)

-87-NII-Electronic Library Service

I.5

X

x

1.0

8 to

Nx

`/

1t

×

"''L-k:Ol;9/t

Nnm6tif;eFvD

Quq=

D2ctrn-.

KATe

---

WAKABAYASHI AUTHORS FLEXURAL STRENGTH e MoNoToNIC LeADtNG O CYCLIC LOADtNG

1.5 1,O

nO'5

io

n

t

1.5

'' ID ' O.5

o

O.4

.--oqto]

g=o.s3

y-q(bi

g.Lo"45

L5

--bq

Cc}o5"bPO.4O.Ge-54

1,5 IP

qsnTlo

O.4 ?=44

op

-.q

(d)

g=,,oO.6

QP

DTU24

ke)

g=Le+45

o

eq

<h)

g#i.5

Fig.13

og?r45

Comparisons

LO

nO'5

1

_o -,5

p

oon

t

-q

Cf)8nto

xxt

[

NLf'

sxx

oA

es34e.6

o

.q

ci)

between

the

oA

a6

g=L5

?=54

experimental n

T

t.5

IP

O.1

ultirnate

o

cg)

8t.o

?=24

7.r"q

(j)

g-L5

strengths and

os

D

T=24analytical

oS ones

(9)

alD

=1.5

(see

Fig,13

h-j),

iii

)

Almost

aLl

the

experimental ultimate strengths of

the

columns with alD==1.5 are

larger

than

the

shear

$trengths

_given

by

the

_prepo$ed

method,

though

the

strength of

the

encased concrete colurnn

is

overestimated

by

Eq.

5. 0ne

of

the

reasons

for

this

is

that

the

steel

tubular

column

is

underestimated

by

Eq.1.

(2)

Nllv,Ko,s,

plts4s

The

validity of

the

"Extended

Superposed

Strength

Method"

was expeTimentally

_proved

on]y

for

these

ranges

in

this

_paper,

It

is

considered

that

these

limitations,

except

DltS45,

do

not cause

inconvenience

to

_practical

design

apptications.

It

is

observed

to

be

necessary

to

extend

the

experimental

investigation

to

short columns wiLh

Iarger

Dlt

ratios

(thinner

steel

tubes).

5. CONCLUSIONS

The

following

conclusions are reached

basecl

on

the

experimental

investigatien

utilizing small scale

test

specimens.

(

1 )

The

decrease

in

the

shear resistance

due

to

cyclic

Ioading

was more

_piominent

for

columRs with

larger

wall

width

to

wall

thickness

ratios and

higher

axial

forces.

After

a

certain

amount

of

decrease

in

the

shear

resistance

of

the

highly

axial

loaded

columns

(NllVh#O.

5>

took

place,

their

hysteretic

loops

became

stable

and an

increase

in

the

shear resistance

due

to

cyclic

loading

at

large

displacement

levels

was observed.

The

cyclic

cleterioration

of

the

short columns

failing

in

shear was

less

than

that

of

the

columns

failng

in

flexure.

(2)

The

ultimate strength of columns whose shear span

to

depth

ratio

is

less

than

1.5

can

be

estimated

by

the

analytic.al method

preposed

in

this

paper.

ACKNOWLEDGEMENTS

The

autho'rs are very

grateful

to

Professor

M,

Tomii

of

Kyushu

University

for

his

helpful

_guidance

and usetul suggestions.

The

authors aLso wish

to

thank

Dr.

A.

E. Aktan'ofUniversity

of

Catifo[nia,

Berkeley,

forhis

editorial asslstance,

REFERENCES

O

Tomii,

M.

,

Matsui,

C.

and

Sakino,

K. ,

"Concrete

_Filled

_Steel

_Tube

_Stiuctufes,"

_Proceedings

ef the

National

Conference

en

the

Planning

and

Design

of

Tatl

Buiidings,

Tokyo,

Japan,

ASCE-IABSE,

August,

1973,

z}

Tomii,

M.

and

Sakino,

K.,

"Experimental

Studies

on

the

Ultirnate

Moment

of

Concrete

Filled

Square

Steel

Tubular

Beam-Colurnns,"

Transactions

of

the

Architectural

Institute

of

Japan,

No.275,

Jan.,

1979.

3}

Tomii,

M.

and

Sakine,

K.,

"Elasto-Plastic

Behavior

of

Concrete

Filled

Square

Steel

Tubular

Bearn-Columns,"

Transactions

of

the

Architectural

Institute

of

Japan,

No,280,

June,

1979.

4)

Tomii,

M.

and

Sakino,

K.

,

"Experirnental

_Studies

_en

_Concrete

_Filled

_Square

_Steel

_Tubular

_Beam-Columns

_Subjected

_to

Monetonic

Shearing

Force

and

Constant

Axial

Force,"

Transactiong

of

the

Architectural

Institute

of

Japan,

No.

281,

July,

]979.

5)

Tomii,

M.,

Sakino,

K.

and

Kiyohara,

K.,

"Experimental

Studies

on

Plain

Concrete

CoLumns

Subjected

te

Menotonic

Shearing

Force

and

Constant

Axial

Foice,"

Transactions

of the

Architecturat

Institute

of

Japan,

No,

_307,

Sept.,

1981.

6)

Sakino,

K.

and

Tomii,

M.,

"Hysle[etic

Behavioi

of

Concrete

Filled

Square

Steel

Tubular

Beam-CoLurnns

Failed

in

Flexure,"

Transactions

of the

Japan

Cencrete

Institute,

Vol.3,

Dec.,

1981.

7)

Wakabayashl,

M.,

"Composite

Structures

_in

Architecture,"

Concrete

Journal,

Japan

Cencrete

Institute,

No.219,

Dec.,

1983.

_(in

_Japanese)

8)

Wakabayashi,

M.

and

Minami,

K.

,

"Rational

_Analysis

of

Shear

in

Structural

Concrete

Columns,"

Disaster

Prevention

Research

Institute

Annuals,

Kyoto

University,

No.24B-l,

April,

1981.

(in

Japanese)

.

9)

Kato,

B.

and

Shohaia,

R.

_, "Strength of

Steel-Reinfored

Concrete

Members,"

Transactlons

of the

Architectural

Institute

of

Japan,

No.266,

April,

1978.

"n

Japanese)

10)

Tanaka,

H. ,

"Proposal

of

Design

Fermulae

of

Required

Web-Thickness

of

Bearn-Column

Connectiens,"

Transactiens

ef

the

Architectural

Institute

of

Japan,

No.207,

May,

1973.

Il}

Suenaga,

Y.

and

Ishimaru,

R.

_, "Kinematic

Analysis

of

Concrete

Members

Under

Combined

Stresses-Part

4-,

"

T[ansactiens

of the

Architectural

Institute

of

Japan,

No.221,

July,

1974.

(in

Japanese)

12)

Wakabayashi,

M.,

"A

_Proposal

_for

_Design

_Formulas

of

Composite

Columns

and

Beam-Cotumns,"

Prellminaty

Report

ef

Second

lnternational

Co][oquium

on

Stability,

Sept.,

1976.

(10)

-89-NII-Electronic Library Service

1

研究論文

1

UDC ：

624 ．

075 ．

24

：

624 ．

014 ．

27

日本逮築学会構造系論文報告集第

353

号

・

昭和

60

年

7

月

　　　　　　　　

定

_軸

力

の

もと

で

_{繰返}

しせ

ん

断力

を

受

ける

コ

ン

ク

リ

ー

ト

充

て

ん

_角

_形

_鋼

_管

短

柱

に

関

する

実験

_的

研

究杖

梗概

）

正会員正会員

崎　　野

石

　　橋

健

久

治

＊＊

義

＃＊＊

　

1 ．

序

　

図

一

1

に

示

す

変形

・

応力（

単調加力

）

を

受

ける

柱

は

，

せん

断

スパン

比

α

／

D

が

2

_{より}

大

_きい

場合

は

曲げ破壊

をおこし

，

a

／

D

が

1

より

小

さい

場合

にはせん断破壊をおこ

す事を文献

4

において

明

らかにした。

　

本論

においては_，

次

の

事を明

らかにするために

行

った

実験的

研

究

について述べ

，

ついでこれらの

実験結果

をも

と

に

短柱

の

終局強度

理

論式

の

検

討を

行

う。

　

1 ）

せん

断

スパン

比

1 ．

5

の

柱

の

破壊

モ

ー

ド

　

2 ）

せん

断破壊

する

短柱

の

復

元

力特

性

　

2．

実験計画

　試験体　本実験

の

実験変数

の

範

囲は

次

の通りである

。

（1 ）

せん

断

スパン

比（

α

／

D

）

：

1 ．

5 （

単調載荷

）

，1

（

繰

返し

載

荷

〉

，

（2 ）

鋼管

の

幅

と

板厚

の

比（

D

／

t

）

：

45

，

34

，

24

，

（

3 ）

N

／

N

。

（

N

。は

中心圧縮耐力）

：

0 〜O．

5．

　

21 体

の

試験体

の

実験条件を表

一

1

に_，

試験体

の

寸法

を

図

一

2

に

示

す

　

制料

　

コンク

リ

ー

ト

の

調合を表

一

2

に

示

す

。

膨

張

材

をセメン

ト内割

で

15 ％混入

した

膨張

セメント

を

用いた

。

　

すべての

_鋼管

は

_{残留応力除去}

のた

め

の

_{焼鈍を行}

っ

た

。

引張試験

により

求

めた

機

械的

性質

を

表

一

1

に

示

す。

　

実験方法

　

図

一

3

に

示

す

加力装置を用

いて

，

図

一

1

に示す逆

対称変形

を

試験体

に

与

えた

。

繰返

し

載荷

の場

合

の

載

荷プ

ログラムを

図

一

4

に

_{示す}

。

　

3．

実験結果

　

せん

断

スパン

比

1．

5

の柱

（

単

調

載荷）

せん

断力

・

部

材角関係

を

図

一

5

に

示

す

。

せん

断

スパン

_比

が

1

と

1 ．

5

の

場合

の

充

てんコンク

リ

ー

ト

柱

のひ

び

われ発

生

状

況を図

一

6

に

示

す

。

せん

断

スパン比

1 ．

5

の

柱

では

，

対角

線

方

向

のひびわれは

見

られ

ず

，

上

下

端

には

塑

性

ヒンジが

形成

されており，

曲げ破壊的

な

破

壊性状

を

示

している

。

　

せん

断

スパン比

1

の柱

（

繰

返し

載荷）

せん

断力

・

部

　t _{本論文} の概要は

，

日本建築学会大会学術講演梗概集〔昭

　　和

55 年

9

月

，

昭

和

56 年

9

月

）

に発

表済

。 e＃ _九州大学　助教授

・

工博 “＊ “ 熊谷組（元九州大学大学院生）

・

工修　　〔昭和

59

年

2

月

24

日原稿受理日

，

昭和

50

年

3

月

14

日改訂原稿　　受理日

．

討論期限昭和 60 年 10 月末日）

材

角

関

係を図

一

7

に

示

す

。

い

ず

れの

場合

もエ

_ネ

ル

ギ

ー

吸

収能力

に

富

む

履

歴

性

状

を

示

している

。

　柱

の

履歴性状

に及ぼすせん

断

スパン

比

の

影響を見

るために

_，

繰返し

載荷

による

耐力

の

劣

下がもっと

も顕著

であった

Dft

が

45

の

柱

について

，

無次元化し

た

除荷点荷

重

と

部材角

の

_関

係

を

図

一

8

に

示す

。

α

／

D

が

1

の

柱

は

，

後

に述べるようにせん

断破壊

したとみなされ_， a

_／

D

が

2

と

3

の

柱

は

曲

げ

破壊

した

柱

で

あ

る。

図

一

8

に

示

されるように

，

せん

断

破

壊

した

_柱

の

繰返

しによる

劣下

は

，

曲げ

破

壊した柱のそれより小さい

。

この注

目

すべき

結果

は_，

D

／

t

が

34

と

24

の

柱

についても

言

える

事

である。

　

4．

短柱

の

終局強度

　

コンク

リ

ー

ト充

てん

鋼管柱

は_，

鉄

とコンクリ

ー

トからなる

合成部材

の

一

種

で

あ

る7 ）

。

合成柱

の

_{終局強度}

に

関

しては

，

若林

・

南

により

理論式

が

提案

されている

。

この

理

論

は

，

加藤

・

称原

が

鉄骨鉄筋

コンク

リ

ー

ト部材

に

関

して

提案

した

理論

91

を拡張し

た

も

の

と考

えられる

が

，

曲げ破

壊

，

あ

るいはせん

断破壊を生

じる

多

くの

合成部材

に

対

して

適

用できることが

示

されているS）

_。

この理

論

によると

，

コンクリ

ー

ト

充

てん

鋼管

柱

の

終局

強

度

は

，

鋼管柱

と

充

てんコンクリ

ー

ト

柱

の

強度

を

累加

することにより

得

られる

。

本節

では

，

この

方法

の

改良

についての

提案

を

行

う

。

加藤

ら

，

若林

ら

，

著者

らの

3 方法

の

違

いは

，

　

1 ）鋼管柱

と

充

てんコ _ンク

リ

ー

ト柱

の

終局強度算定法

2 ＞両者

の累

加

の

方法

，

にある

。

　

鋼管柱

の

終

局強

度

　

図

一

1

に示す応力を

受

ける

鋼管

柱

の

終局強度

は，

下記

の

仮定を設

けた

極

限

解析

10）による

と

1 式

によって

与

えられる

。

　1 ）

せん

断応力度

は図

一

9

に

示

すようにウェブに

一

様

に

分布

する

。

　2）

曲げ

モ

ー

メン

ト

。

Mw

による

直

応力

scrWM

と軸力

sNw による

．

，σWN は，

図

一

9

に

示

すように

一

様

に

分

布

する。

　

3 ）降伏条件

は

2 式

により

表

される。

　若林

らの

_方法

において

も

，

1 式

と同

様

な

式

が用いられる。

加藤

らの

方法

においては，

鋼管

は

軸

力を

負

担せ

ず

，より

簡単

な

静的許容応力場が仮定

される

。

加

藤

らの

方法

と

1

式の違いは

，

実験値

と

解析値を比較

した

計算例

にお

一

₉₀

一

N工工

一

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