建知工業大学研究報告 第
27
号 平 成4
年107 論文
EFFECT OF SIZE AND SLENDERNESS RATIO
OF SPECIMEN ON STRESS-STRAIN BEHAVIOR OF
CONFINED HIGH STRENGTH CONCRETE
Sachio
KOIKE
長 and Shigemi七su HATANAKA普 普中心圧縮を受けるコンファインド高強度コンクリート
の塑性変形性能における務状ー寸法効果
小 地 挟 千 期 * 畑 中 重 光 * *
A series of uniaxial compression七es七s of confin巴d concre七es have been
carried ou七七o examine七he siz白 色ffec七s on七heir compressive behavior. The
s七reng七h of concre七e has been varied from abou七300七o 700 kgf/巴m2. Based
on七he七es七 resul七s
，
discussion has be巴n carried ou七 on七he rela七ionbe七W母、号n concre七e s七reng七h and七he size effec七s on七he compressive s七reng七h
，
E七rain a七七he p巴ak s七ress
，
and s七ress-s七rain curve of confined concre七e.1.INTRODUCTION
For the analytlcal discussion of rotation capacity of RC beams
，
it is very important to understand quantitatively the conflning effects of lateral reinforcement on the ductility of concrete in the damaged compressive zone of RC members. The authors have already examined the plastic deformation behaviors of confined concret日 程nder uniaxial compression and RCbeams under flexure
，
and reported that，
for both cas~s ， specimens showed mor8 brittle behavior with increasing size of spec!men， regardless of the spacing of申 Department of Archl tecture
，
Facul ty ofEnglneerlng， Aichi Institute of Technology
市串 Department of Architecture， fi'aculty of
Engineer!ng
，
Mie Universltylateral reinforcement and curing condition [1-3] .
Recently， high strength conCf自te up
to 600 kgf/cm2 is being used practlcally
ln high rise bullding constructlon in Japan. The discussions in the earlier reports by the authors are
，
however，
limlted on the concrete of water-cement ratio of 55% or compressive strength of about 300 kgf/cm2. The purpose of the present study is to examine the effects of size and slenderness ratio Cheight -width ratio) of specimen on the stress-strain behavior of confined concrete under compr官ssion， taking the compresslve108 愛知工業大学研究報告，第27号B，平成 4年， Vo1.27-B， Mar.1992 2，EXPERIMENTAL PROCEDURES 2. 1 OUTLINE OF EXPERIMENT Outline of the uniaxial compression test of confined concrete prisms is shown in Table 1. Testing variables include the section size Cbxb， b=9.7， 15， 20， and 30 cm) and the heightCH)-widthCb) ratio of speclmen(H/b=2 and 3)， water-cement ratlo CW/C=32， 42， and 55%)， and spacing of hoops CS=b/4， b/2
，
b， and infin!ty). The size of specimen and the arrangement of hoops are illustrated ln Flgs.l and 2， r日spectively， Diameters of hoops were sel自cted for the lateral reinforcement ratio CAs/Acv， where，
As: cross-sectlonal area of hoops，
Acv: vertlcal cross-sectional area of core ，concrete) to be approximately 0，3 % fOf the specimen 曹ith hoops of S=b， The mechanical pfoperties 01 hoops used are shown in Table 2曹ith confining stress ind冒x C (1yAs/Ac).Judging from the ind日x，
conflnlng stress on the sp日clmens wi th 30x30 cm section(<t13 mm bar was used as hoops) is assumad to be a 11tt1e larger than the others. The number of sp8cimens prepared for each combination of parameters was 2， and the total number was 192.2. 2 FABRICATION AND CURING OF SPECIMENS Ordinary Portland cement， river sand (<5 mm)， crushed stone <10目20 mm)， and superp1astlcizef Conly forW/C=32 and 42 % ) 曹ere used for the fabricatlon of concrete. Slump was deslgn哩dto be 1自 cm， Concrete曹as cast horizontally for a11 the speclmens. Three batches of concrete for each water-cement ratio 胃ere mixed by using the 600 litter Smlth typ骨 mi)(er. Varlation of the averaged compressiv官 strength of<t10)(20 cm concrete cy1inder was 曹ithin 3.2 % between the batches. All the specimens were cured in an air conditloned room (20土I"C and relative humidlty of自5士5%) unti 1 the tests
，
which 胃ere carried out at the age of 6 明日eks.Tab1e 1 Outline of compression test of concrete prisms Size of pris園 日∞p Longitudinal bar Sectio目 Height Di趨eter Spacing Dia配t号F Curing bXb (c園) H=3b (c圃) H=3b(CIII) φ {睡)
s
(幽) condition 7.3X 7.3 14.5 21.9 3.2 b/4 9.7X 9.7 19.4 29.1 3.9 ln a.ir 12.5X12.雪 24.9 37.5 4.9 0/2 2.7 15. OX15. 0 30.0 45.0 5.7 b In胃ater 20.0X20。
圃
40.0 60.0 8.0 pla.inTable 2 Mechanical properties of hoops No姐i目11.1 Me錨 日reddia配ter YKId {臨strf/官E略圃t2h) 闘畠σx 目i醐園色gstf/rE昭}cdth EIOB
。
Z晶}tio田 6{同y 圃Af/s/cEFAE) dia圏eter (醐) C1y φ3.2 3. 1型 2420 3430 29図2 6.37 φ3.9 3.明。 2280 33開 40.9 5.倒 φ4.9 4.98 1940 3070 41. 6 4固19 φ5. 7 5.93 2雪印 3890 31. 5 6.34 φ8.0 7.96 2650 3530 32.5 5.71 問。tes] As:Sectio拠1area of h∞
'p. Ac:Area of norizonta.l section of core concrete中心
E
蒲を受けるコンファインド高強度コンクリートの塑性変形挙動の形状・寸法効果1
0
9
2
.
3
M
E
T
H
O
D
S
O
F
L
O
A
D
I
N
G
A
N
D
M
E
A
S
U
R
E
M
E
N
T
T
h
e
m
e
t
h
o
d
o
f
s
t
r
a
l
n
m
e
a
s
u
r
e
m
e
n
t
o
f
c
o
n
c
r
e
t
e
p
r
i
s
m
s
i
s
i
l
l
u
s
t
r
a
t
e
d
l
n
F
i
g
.
3
.
T
h
e
s
t
r
a
i
n
m
e
a
s
u
r
l
n
g
r
e
g
i
o
n
s
(
1
町)f
o
r
t
h
e
s
p
e
c
l
m
e
n
s
o
f
H
/
b
=
3
w
e
r
e
2
b
a
n
d
2
.
8
b
i
n
t
h
e
〆-b-
プ(
cm)
b
=30.0
20.0
1
雪.
0
9
.
7
(
a
)
H
/
b
=
3
m
i
d
d
l
e
h
e
i
g
h
t
o
f
t
h
日s
p
e
ci
m
e
n
s
，
w
h
i
le1
・
w
a
s
1
.
8
b
f
o
r
t
h
e
s
p
e
c
l
m
e
n
s
o
f
H
/
D
=
2
.
M
o
s
t
o
f
t
h
e
s
p
e
c
i
m
e
n
s
w
e
r
e
l
o
a
d
e
d
i
n
a
n
a
c
t
u
a
t
o
r
(
l
o
a
d
i
n
g
c
a
p
a
c
l
t
y
:
2
0
0
t
f
)
u
n
d
曹r
t
h
e
c
o
n
s
t
a
n
t
s
t
r
a
i
n
r
a
t
e
o
f
a
b
o
u
t
l
x
l
0
-
3
Imin.t
i
l
l
t
h
e
s
t
r
a
l
n
o
f
t
h
e
2
b
r
e
g
i
o
n
メ ーb
ー ヂtU
口
日
日
(cm)
b
=30.0
20.0
1
5
.
0
9
.
7
(
b
)
H
/
b
=
=
2
Fig.l Size of concret
日prisms
日豊目ミ日~~]口
b- _ bS
=
'
:
:
'
S
=
-
:
-4 2S=b
日ain b b S=- S三 一4
2
S=b
P
l
a
訂1(
a
)
H
/
b
=
=
3
(
b
)
H
/
b
=
2
Fig.2 Arrangement of hoops
i
匝
(
a
)
H
/
b
=
3
，
l
o
=
2
b
a
n
d
2
.
8
b
(
b
)
H
/
b
=
2
，
l
o
=
1
.
8
b
Fig.3 Method of strain measurement
愛知工業大学研究報告，第27号B，平成 4年， Vol.27-B， Mar.1992
(2)Straln at peak stress
Flgures 5(a) through (b) show the effect of the pitch of hoops on the re1ation bet胃een strain at the peak stress
(e m) and spec!men size for th日 case of
H/b=2 and 10=1. 8b. 1 t i s shown tha t the value of e m general1y decreases 官ith
increasing size of specimen
，
regardless of 110reached the specified straln (e=15)(10-3).
Large specimens 宵hose 10呂d bearing
capacity isass日間宮d to be larger than 200
tf were tested in an ordinary type hydraulic compresslon testing machine
(loadlng capaclty: 600 tf).
3. TEST RESULTS AND DISCUSSIONS
9.7 15.0 20闘
o
30，0 WIDTH(cm)， b 900 n u n u n u n u n u n u ゥ ， R J ペ コへ
N
5
b
S
F
o
z
目白昼
o
υ
3.1 STRESS AND STRAIN AT PEAK POINT
Figure 4 sho曹s the effect of 曹
ater-cement ratio (W/C) on the relation between compr自ssive strength and sp邑clmen size.
The compressive strength is almost constant regardless of the specimen size in case of W/C=55 %. However
，
in the high strength concrete of W/C=32 %. the compressiv日 strength gradua1ly decreasesas the sp母cimen size increases
，
thecompressiVB strength for the specimens of b=30 cm belng smaller than that for the spec Imens of b=9.7 cm by about 10 % on the average.
(l)Compresslve strength
Fig.4 Effect of water-cement ratio on r巴lation between compressiv巴
strength and specimen size (H/b=2)
O---OS=b/4 b一一寸与S=b〆/2 口一ー一口S=b 0一一一OS=plain ム、、 ¥、、、八 臼 -
ゐ---o_ー[凶
- 吋 』 一 一 一 - - ^ ]一一ー一一一_"， 0-一ー町一司右ト一一ーーモト一一ーー一一ー一-0 企 9.7 15.0 20.0 30.0 WIDTH (cm) ， b740
。
伊 吋 X 3.5 、ー-' 2 3 0 [/) じ~ 2.5 〈 民4 0..2.0 ~z
:
1.5 b司 .. 戸、
出1.0 ui土木、
二一』チトーιで一一一ーが」ー」こ:エ三弓
U一一一σ Sニb/〆4 A一一世，S=b/2 0--一口S=b Cト一一oS=plain 9.7 15.0 20.0 30.0 WIDTH(cm)，b~
3.0担
当
2.5 同 仏 2.0 ~Z
1.5 〈5
1
0
。一一-oS=b/4 止一一-t;S=b/2 口一--OS=b 。一一一OS=plain持
b
ョ
ー¥ヒ-.こ三司
9.7 15.0 20.0 30.0 WIDTH (cm) ， b X 3.5~
3.0包
3
2
5
0..2.0 』 q Z 1.52
1
。
←
凶 (c) W/C=55% e m and Fig.5 Effect of pitch of hoops on r百lation betweenspec imen s i ze CH/b=2， 10=1. 8b) Cb) W/C=42% Ca) W/C=32%
中心且講を受けるコンファインド国鍍コンクリ トの塑性期持輸の形状司寸法効果
1
1
1
同/C r a t 10. Th e v a 1 u e 0 f e m f 0 r t h e sPBcimens of b=30 cm is smaller th畠n that for the specimens of b=白自7 cm by about 15 % ， which is the same tendency in the earlJer experiment of normal strength concrete [31. No te that the increment of e m due to hoop reinforcement d自creases as明/C ratio becomes small.Almost the same も 800 n u n u n u n U 内 U ハ U 6 4 2 M n 日 υ ¥ 柏田﹄)回目凶同ト回 1:>800 円 u n u n u n u n u n U 6 4 2 州 竹 田 υ ¥ 刷 出 ﹄ 一 回 凶 凶 同 ト 凹 1:>800 円 U n u n u n u 円 U 円 U 6 4 2 N 自 υ ¥ 相国﹄一目的同凶ト目
。
ち 10 15 STRAIN (XI0-3 )，
ec (a)W/C=32% 司自-~b= 9.7cm 園 田 目--b=15.0cm 回 目--b=20.0cm -0田-b=30.0 cm。
5 10 15 STRAIN (XI0-3 )，
ec (b) W/C=42%-
----b=15.0cm一
一
一
b= 9.7 cm 自 由 圃 白 血b=20.0cm 宇 司 @ 田-b=30.0 cm。
5 10 15 STRAIN (XI0-3 )，
ec (c)W/C=55%Fig.6 Effect of specimen size on stress-strain curv巴
m/b=2， S=b/4)
tendency is obtained for the specimens of H/b=3.
3， 2 STRESS-STRAIN CURVES OF SPECIMENS WITH DIFFERENT SIZES
Fi gure s 6 (a) through (c) show the effect of the specimen size on the
stress-1:>800 n v n u 円 U n v n u n U 6 4 2 N E υ ¥ 柏 田 ﹄ 一 凹 的 国 民 ト ∞ 1:>800 n U 円 u n u 円 u n u n U 6 4 2 M W巨 υ ¥ 刷 出 ﹄ 一 目 的 凶 凶 ト 目 1:>800 n u n u n u n u 円 u n U 6 4 2 代 田 U ¥ 阿 国 主 的 回 国 同 ↑ m ---b= 9.7cm E 甲 申 司b=15.0 cm _.-b=20.0cm - 0
一
一
b=ヨO.Ocm。
5 10 15 STRAIN (XIO-3 )，
ec (a) W/C=32% 国--b= 9，7cm一
一
一
-b=15，0cm _ . 申 事b=20.0 cm - 0自 由b=30.0 cm。
5 10 1日 STRAIN (XI0-3 )，
ec Cb) W/C=42% m m m m c c c c マ ' n u n u n U 9 5 0 0 旬 i つ G 巧 喝 J bbbb一
一
一
一
一
一
一
一
。
雪 10 15 STRAIN (XIO-3 )，
ec (c) W/C=55%Fig.7 Effect of specimen size on stress-strain curve
1
1
2
愛知工業大学研究報告，第27号B，平成4年， Vol.27-B， Mar.1992strain curve fOf the case of H/b=2 and
S=b/4. It is shown that the shape of
stressd~scendlng portion becomes steeper
with lncreasing s!ze of sP8clmen，
independently ofW/C ratio. The amount of reductlon of compressive toughness Carea under the stress-strain curv日) due to the
lncrease in the specimen slze Js not so dlfferent from each other set of the curves of Figs.6 (a) to (c).
As is obvious from the comparison between the curves in Figs， 6 and 7， such size effect on the stress-strain curve is mOfe remarkable for the speclmens with densely arranged hoops， Thls is consldered
due to the fact that the conIining effect by hoops is affected by the magnitude of spacing ltself between hoops
，
as well as 円 υ n u n u n u 円 u n u n u n u o o ζ U A A 1 勺 ム h v h 一 N E υ ¥ 柏田﹄一凶回凶出ト∞ n u n u n u n u n u n u n u n U 8 6 4 2 b 二 m u 臣 υ ¥ 同 切 さ 目 的 同 国 ↑ ∞。
5 10 STRAIN (xI0-3 )，
ε 15 S/b r a t i 0 . N 0 t e t h a t a 11 t h e s p e c i m e n s a r e made of the same concrete with the same size of aggregate，3， 3 STRESS-STRAIN CURVES OF SPECIMENS OF DIFFERENT SLENDERNESS RATIOS
Cl)Effect of height-胃ldth ratio Figures 8(a) and Cb) show the effect of height-宵ldth ratio CH/b) of speclmen on the stress-strain curve for the case of b=9， 7 cm， Straln measurement length 0.) is 1.8b for specimens ofH/b=2， and 2，8b for speclmens ofH/b=3， It is observed that
，
independently ofW/C ratio，
the descending portions of stress山 straincurv日Sof specimens ofH/b=2 are much 1ess steep than those of sp6cimens ofH/b=3， n u n U 円 u n u n u n u n u n U 8 6 4 2 b -一 N 日 υ ¥ 同国﹄一回目回出↑ ω
一-
H/b=2 (lo=L8b)ー
-
-
-
H/b=3 (.to=2.8b) S=b/4 S=plain (a) W/C=32%。
5 10 STRAIN (XI0-3 )，
e 15 Cb) W/C=42%Fig.8 Effect of h日ight-width ratio (H/b) on stress-strain curve
(b:::9，
7
cm) 0 0 0 o n u n u n u n u B 6 4 2 b -一 w 自 υ ¥ 刷出﹄一目的凶凶↑回ー
一
一
H/b=3(lo=2b) H/b=3 (to=2.8b) S=b/4 S=plain一
一
一
H/b=3(.to=2b)一
一
-
-
-
H/b=3 (.to=2.8b)。
5 10 STRAIN (XI0-3 )，
e 15。
5 10 STRAIN (Xl0-3 )，
e 1ち (a)W/C=32% (b)W/C=42%Fig.9 Effect of strain measurement length (10) on stress-strain curve
中心圧縮を受けるコンファインド高強度コンクリートの塑性愛尭縛輔の形状・寸法効果 113 b s=~
4
b 2 b p l a i n (a)W/C=32% b4
b 2 b p l a i n Cb)W/C=42%Fig. 10 Fai lure pattern (b=20 cm)
(2)Effect of stra!n measurement length
Figures 9(a) and (b) show the effect of strain measurement length (10) on the stress-strain curve for the ease of H/b=3 and b=9.7 cm. The stress descending portions of stress-strain curves of 1.=2b are less steep than those of lo=2.8b
，
regardless of W/C ratio. This is considered due to the fact that the occupying ratio of undamaged zone within the strain measurement region is larger for lo=2.8b than that for 10=1. 8b. Figures 10 Ca) and (b) show examples of fa! lure pattern of the specimens of b=20 cm.Note that this tendency becomes a little less remarkable as spec!men size increases. Fl.¥rther
，
the stress descending portions of stress-strain curves measur日dbetween the load!ng plates were a l!ttle steeper than those from both 1
・
=2.8b of H/b=3 and 10'=1. 8b of H/b=2，
independ日ntlyo f W/C r a t
!
o.4.CONCLUSIONS
The following conclusions can be drawn from the present study.
l)The compressive strength !s almost constant regardless of the sp日clmen s!ze
!n case of W/C=55 %. However
，
in the high strength concrete of W/C=32，
%
the compressive strength gradually decreasesas the specimen size increases
，
the compressive strength for the specimens of b=30 cm being smaller than that for the specimens of b=9.7 cm by about 10 " on the average.2)The strain of thB peak stress (εm) for the specimens of b=30 cm !s smaller than that for the specimens of b=9.7 cm by about 15
，
%
rBgardless of W/C ratio，
wh!ch is the same tendency in the earlier expBriment of normal strength concret日[3]. Note that the increm目nt of e m due to
hoop reinforcement dBcreases as W/C ratio becomes small.
3)The shape of stress descending portion becomes steeper with increasing size of specimen， independently of W/C ratio. 4)The size effect on the stress-strain curve is more rBmarkable for the spec!mens wi th densely arranged hoops. It is considered due to the fact that the confining effect by hoops is affected by the magnitude of spacing itself between hoops.
REFERENCES
DKoike
，
S.，
Hatanaka，
S and Okuya，
Y.，
"Size Effect on Plastic Deformation Capacity of Reinforced Concrete Beams，
"
Trans. of JCI，
Vol.11，
1989，
pp.363-370.1
1
4
愛知工業大学研究報告，第27号B，平成 4年， Vol園27--B，Mar冒・1992on Stress-Strain Behavlor of Plain and Conflned Concrete Under Compresslon
