中心圧縮を受けるプレーンおよびコンファインドコンクリートの塑性変形挙動における寸法効果

(1)

愛知工業大学研究報告

第25号B 平成2年 163

S

i

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宜

e

c

ton P

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a

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i

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Deformation Behavior o

f

P

l

a

i

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品

目

edConcretes under Compression

中心圧縮を受けるプレーンおよびコンファインド

コンクリートの塑性変形挙動における寸法効果

小池狭千朗@畑中重光*

Sachio

KOIKE

and Shigemitu

HATANAKA

*

The purpose of the present study is to examine the e任巴ctof the specimen size and the aggregate size on the inelastic stress-strain behavior of both plain and confined concrete. The following statements can be drawn from the study.

1) It can be concluded that the behavior of the microconcrete in which the maximum size of coars巴aggregateis reduced in proportion to the size of specimen may be more

ductile than the co即日tein actual structural members

2) The behavior of confined concr巴tebecomes more brittle with increasing size of

specimen r巴gardlessof the spacing of hoops

1. INTRODUCTION

Sma11 sca1ed specimens are usua1工y used for 七he test of R巴infor口ed Concre七日

(RC) s七r凹七世es and members

，

because of the easines日of conduc七ing experimen七日

[1

，

2]. However

，

i t is considered七ha七七here exis七日 the eff巴C七of 七he size of a specimen on七he strength and deformation properties of concre七巴 [3， 4]. To e1工mina七e七he size effec七， m工croconcre七e in which七he size of aggrega七es is reduced in propor七ion to七he size of a speclm巴n is of七巴n us巴d for 七he sma11 sca1ed specimen[5，6]. It is， howev巴r，

s七il1ques七工onab1巴whe七her or no七七he s工ze effe巴七 can be comp1ete1y e1imina七ed by uSlng七he microcon口rete.

Litt1e experimenta1 data is avai1ab1e concerning七he siz巴巴ff巴巴七 on七he s七 ress-strain behavior of p工ain and confin巴d

concre七es，whi1e a 10七of da七a exis七

建築学科

concern工ng七he size effec七 on th巴

compressive streng七h of p1ain concret巴[7，8，9，10]. The purpose of七he presen七s七udy is七o examine七he effec七of the spec工men size and the aggrega七日 Slze

on七he ine1as七ic s七ress-s七ra工n behavior of bo七h p1a工n and巴onfined巴oncr巴tes.

2. SIZE EFFECT OF PLAIN CONCRETE 2.1 Ou七1ine of experiment

The de七ai1s of p1ain con巴rete

specimens are日hown in Tab1e 1. The

七es七variab1es工nc1udeもhe sectiona1 sh旦pe

of a specimen (c工rc1e and square)，七he size of a specimen (prisms: bxbx3b

，

b=4.5

，

5.6，7.3，9.7，12.5， 15.0cmj cy1inder: heigh七(h)/diameter(d)=2j d=7.5， 10， 15cm)，七he maximum size of aggrega七e(中 a=5

，

10

，

20， 25， 30mm)， and wa七er-cemen七 ra七io (W/C=45

，

60

，

70%). The number of specimens prepared for each combina七ion of variab1es was 20

，

and七he tota1 number was 1800. Cylind日rs w巴re cas七ver七ica11y

，

prisms

(2)

164 小池狭千朗・畑中重光

were cas七horizontally.

Ordinary Portland cement

，

river sand (max工mum size: 5mm)

，

and river gravel

(size range: 5 'v 30mm) were used for七he

fabrica七ion of mortar and concrete. Slump was designed七o be 15cm. Alユ七he specimens were stripped a七七he age of 3 days

，

and七hen cured in a room a七a 七empera七ure of 20:t20C and a rela_七ive

humidi七Y of 75:t10%山1七il七he七es七日. The 七es七日 were carried ou七a七七he age of 6 weeks.

The specimens were loaded under七he cons七an七日七rain rate of abou七 1x10-3 /min. up 七o 七he specified longi七udinal

B七rain( E) of 1 Ox1 0-3 by using a high

rigidi七y 巴ompressive 七es七ing machine.

The longi七udinal s七rain wa日measured by a

couple of deforma七ion七ransducers (measuremen七 lengths were 2b for prisms and (h-2)cm for cylinders).

2.2 Test results and discussion (1) Compressiv巴 s七reng七h

Figures 1 and 2 show七he eff巴C七of the specimen size on the compressive E七reng七h(Fc) of prisms and cylinders

，

respec七ively. 1七 is shown in these figures，七ha七i)七he size effec七of prisms and cylinders on七he compressive streng七h is quite similar

，

i.e.

，

the compressive s七rength increases wi七h increasing specimen size (for七he same maximum size of aggrega七e (中 a))

，

and ii) 七he compressive s七rength decreases with increasing value of中a for七he same size

Table 1 De七ailes of plain concre七日 specimens

Size of prls. Size of cylinder lfater-c伺陸自t Maxl ..周size d※Xh ratio

。

. faggregate bXbxh

。

₍_l₌_E₃_圃_b_}_} ₍_h₍₌_E₂_圃_d₎₎ 官

'

/

C

(%) φa (_) 4.5x 4.5XI3.5 φ7.5X15 45 15. 25 5.6X 5.6XI6.8 7.3X 7. 3X21.9 _{φ10 x20} 肱>rtar 60 10. 15. 20. 9.7x 9. 7X29. 1 25. 30 12. 5x12. 5x37. 5 _{φ15x 3}₀ 70 15. 25 15.Ox15. OX45. 0 ※d: di細eter n u n u n u n υ 5 0 5 0 q J q J 司 L っ “ ( N E U ¥ 相同ぷ)司ト

o z

ω

凶ト ω 150 4.5 7.3 9.7 1 2.51 5.0 WII>TII (cm). b

Fig.1 Compressive s七rengthof plain concre七e versus sec七ionwid七h of specimen (prism) 400叫 n u n u n リハ υ Z J n u r つ n u q J 司 J 司 4 司， h ( 同巨 U ¥ L H 凶ぷ)ヱト

o z

ω

凶ト ω 150 CyJ inder W/C=60% 7.5 10 15 DIA~1E TER(crn). d n-1' ・ 1 a r a--e - ム、 q 咽 d D A n n ・ 1 f -0 1 ム 0 ・ 1 v u 七 C -n c r t + u e g o s n n e e m T E -七 u c 恩 M g u o u r p み e e s v v ・ -P 4 s e o 貝 UW ふし e e r r r P A C e m n 七 o o e c c m n d g b - 工 F

(3)

日P白cimens (d=1.25'V 15cm) and coarse

aggrega七es (中aニ2.5'v 10mm)圃 In 七heir

tes七日， i七日as found七ha七 th巴 compress工ve

E七r巴ng七h of concre七日 was cons七ant or ユ_ncreasedw工七h the incr巴ase in 七he size of specimen for the constant vaユue of中a (where

，

d/中a=5'V60). Those specimens

were巴ured in water and七ested in dry

condi七ion.

165 中心圧縮を受けるプレンおよびコンブアインドコンクリトの塑性変形挙動における寸法効果

七he all of spe巴工men. Note 七ha七

specimens were cured工n a工r.

In 七he presen七 experiment，七h巴

compressive streng七h of both mor七ar (d/中a=9'v 30 ) and concrete (d/中a=1.5'V15)

specimens 工ncrease with th日 increase in

七he sユze of specimen r巴gardl白ss of七he

value of d/中a. This七endency is different from 七he七巴E七 resul七日 ob七ained by Tanigawa 巴七 al

，

・

and is 日im工工ar to

the resul七日 ob七aln巴d by Mori七a et al.， in spi七日 of the fac七七ha七七he curing conditions of concre七es by七he au七hors and Mor工七a巴t al. are differen七.

Tanigawa e七aL [9) repor七巴d，based on the工r七es七 resul七s，七ha七七he size effec七

in 七he compressi v巴 streng七h of concrete

could be expressed by the product of the coefficien七r巴presen七ing七he巴ffec七inもhe compressive s七reng七h of mortar matrix and

もhe0七h巴r coefficien七represen七ing七he

effec七 of d/中a ra七io (where ， d: diame七er of sp巴cim日n，中a: maximum s工ze of

aggr巴ga七日)，工.e.七he effec七of geometrical he七erogene工七y. According to 七heir proposed model reflec七ユng七he above findings，七h巴 compressive s七T巳ng七h of

concrete increases wi七h 七he incr巴ase in

七he size of specimen for七he value of d/中a sma工l巴T 七han abou七 8，and decreas巴s wi七h

七h巴increas巴in七h巴size of specimen for

七h巴value of d/中a grea七er七han about 8. In 七he七日日七日 conduc七ed by Tan工gawa e七al.，

the specimens were cured工n the room at a

rela七ive hum工dユ七y of ヲO士5%。 Fur七her experimen七al investiga七ion is required for七he effects of curing and testing condi七ions on七he size effec七，

which are considered to affec七七h巴

hydra七ion of cemen七 and drying shrinkage Mori七a e七 al.[10) conducted an

experiment on 七he size effect of concre七日

using various sizes of cylindrical

Cy 1 iロder W/C=60%

正

三

3

品a(mm) 嘩ー一--日ORTAR 0----0 10

。

一

-

0

15 A----.t..20 ムー一-a25 0---030 7.3 10 1 5 DIAMETER(cm)， d 4.0 5 0 5 0 5 ペコ司コつ -つ -1

一

EUJmu1 。 [ × 一 Z H ︿ど↑∞

ヘ¥仁三

3

5

¥九---.. 3.5 5 U ;- 3.0

。

， . ...， X 2.5 Z ト.... 〈 Eピト (J) 2.0 1.0 1.5 1.0 4.5 7.3 9_7 12守515.0 WI DTH (cm) ， b

Fig.4 Strain( E m) a七maximum compressive

E七ress of plain concrete versus

se巴七ion diameter of specimen (

巴ylind巴r) Fig.3 S七rain(E皿) a七maximum compressive

s七ress of plain concre七e versus sec七ion wid七hof spe巴i盟en

(4)

166 小池狭千朗。畑中重光

of harden日d concrete according七o the

spec工m巴n s工ze.

(2)

s

七raユn at maximurn compressive s七ress Figures 3 and 4 show七he effec七 of spec工men size on the s七ra工n( Em) at

maximum compressi ve stress of prisms and cy1inders

，

respec七工ve1y. Foユ工owing sta七emen七日巴an be drawn from七he figures。

i) The s工ze effec七日 on 七he日七rain at maximum compressive stress observed for prisms and cy1inders are very simi1ar. As shown工n Fig.3，七he va1ue of E m of

巴oncrete increas巴日 with increasing size of specimen for b=4.5cv 9.7cm

，

whi1e i七 is a1mos七巴ons七ant for b=9.7cv15.0cm. Qui七日 simi1ar tendency is observed in Fig.4.

1工)The va1ue of Em of concre七e d巴creases with工ncreasing va1u巴 of中a for

七he same siz巴

of spe巴imen.

iii) The va1ue of E _ of mor_m 七ar decreases wi七h increasing size of specimen園

Mor工七a e七 a1. [10

1

reported 七hat any significant effec七 of 七he spe巴imen size

(d=1.25 'C15cm) on 七h巴 va1ue of E m was no七

obs巴rved for th巴巴oncrete of same mix七ure (中a=2.5

，

5 or 1 Omm) • A1日0，工t was

reported 七hat in 七he m工croconcr巴七e (d/中a=5

，

d=1.2ラcv15cm)

，

the va1ue of E m became sma1

ユ

巴

r wi七h工ncreasing size of

specimen. In七he resu1七of七he presen七 experユm巴nt

，

any significant size effec七on the va1ue of E m was not observed for七he

円 U 円 u n u n u n u n u 門 u n U 4 ゐ q J 内 4 T よ b

-一

NEU¥ し円切さ

ω ω

凶肖ト

ω

b (cm) 4.5 5.6 ートー→ー 7.3 一一一 - 9.7 -ー一ーー-12.5 一一・・ー 15.0

。

2 4 6 8 10 STRAIN IXIO-3 )，巳

Fig.5 S七ress-s七rain巴urve of pr工自由

of中a=2ラ皿皿

microconcre七日 (see Fig.7(a) to 7(c)). (3)Stress-s七rain己urve

Figure 5 shows the effec七of spe巴工men size on 七he stress( σ)一日七ra工n(E) curv巴 (hereinafter

，

σ -E curv巴) of七he prisms for 中a=25mm. 1七is shown tha七七he compressi ve s七reng七h and in工七ia1 modu1us of e1astici七y become 1arger

，

and the slop巴 of stress descend工ng por七ion becomes s七eeper wエ七h increasing size of 日pec工m巴n.

T h e σ -E curves converge at E =(3cv4)x10-3

，

which is simi1ar 七endency observed be七ween 七he curves of concr巴七es of diff巴ren七

w

/

c

or compressive strength.

Figur巴

6

shows 七he effe巴七 of the va1u巴 of中a onσ-E curve of the prisms

of b=7.3巴m. The compressi v巴 S七T巴ngth and七h巴日七rain a七 maximum compressive str巴ss become sma1ユer

，

and the slope of

s七ress descending por七ion becomes 1ess s七eep to a srna11 extent wi th incr巴asing

va1u巴 of 中a.

Figures 7(a) 七o 7(c) show cornparisons of the σ -E curves of con口retes having

a1rnost sarne b/中a ra七io. The cornpressive s七rength日 decrease and七he des巴ending por七ions of σ -E curv巴 show

more ducti1e b巴havior for七he sma11er

va1ue of b or 中a. Hence

，

i七 can be conc1uded 七ha七七he rn工croconcr巴もe provides rnore duc七i1e behavior than th巴concr巴七e in ac七ua1 s七ruc七ura1 rnernbers.

円 U 円リ円 U n u 門 u n U 4 3 2 b h F E U ¥ L H 切ぷ φa (田コ) 一一一一一10 一一ーー一一15 -<e--e--+-20 一一一- 2 5

、、ご恥ト¥

一一一- 3 0

、、くミ込』

一毛当主主主宮 ω ~ 100 E己ト (J) 2 4 8 10

。

6 STRAIN IXI0-3 )

，

E: m C M ・ 1 T P F 4 0 e v r u 巴 n . 工 a r m

t

c

B つ J S 7 s= e 司D T 4 u p ム cuo 〆 b u u - 工相 r

(5)

中心圧縮を受けるプレンおよびコンブアインドコンクリートの塑性変形挙動における寸法効果 167

30 SIZE EFFECT OF CONFINED CONCRETE

301 Ou七工ine of exper工ment

The details of conf工ned concre七e are shown in Table 20 Th巴七es七variab工巴B

include 七he s工ze of a specim巴n (bxbx3b

，

b=7 .3

，

9.7

，

12.5

，

1 5 .0

，

20.0巴m) and the spacing of hoops (S=b/4

，

b/2

，

b

，∞)固

n u n u n u n u n u n u n u n U 4 A 司 J 円 4 T よ b ‘ 一 N g u ¥ 刷出品一

ω

∞同凶ト

ω

b (cm) ーーー- 0 -一一 15.0 一一一一 12.5 -ー一一一 7.3 一一一一一一一一 4.5 φa b/φa (mm) 30 5.0 25 5.0 15 4.9 10 4.5

。

2 4 6 8 STRAIN(XIO-3_j

，

_e (a) b/中a=4.5"05.0 b n u n u n u n u n u n U A & ペコ円 A J 刊日 U ¥ L H 凶ぷ φa b/φa (mm) 20 7.5 15 6.5 10 7.ヨ ul

2

1 00 凶ト [J}

。

8 10 2 4 6 STRAIN (XIO-3_j

，

_e (b) b/，中a=6.5'V7.5 ハリハ U n u n u ハリハ u n u n U A 吐 q J η 4 1 ょ b 、一円巨

U

¥

い円切ぷ一

ω ω

同出ト

ω

b (cm) 一一。一一 15.0 189 031

。

2 4 6 8 10 STRAIN(XIO-3_j， _e (巴)b/中a=8.3"010

Fig.7 Comparison of s七ress-s七rain curve of巴on巴re七eof al回os七日ame b/中a ra七io

The size of specimens and七he arrangement of hoops are scherna七ically shown in Figs.8 and 9

，

respec七ively. Diarne七ers of hoops wer巴日巴lec七巴d f 0 r 七h巴 la七eral reinforc巴I日 nt ra七io (Ah/Ac' wher巴， Ah!

cross一日巴巴七ional ar巴a of hoops

，

Ac ver七ical cross-sec七ional area of specir附 1)

to be approxirna七ely 003% in 七h巴 ca日巴 of 七he specimen wi七h hoops of S=b. The number of sp巴cimens prepared for each

combina七ion of variables was 12

，

and七he 七o七al number was 240. ヤva七巴r-cemen七 ra七io was se七七o 55%. The yユeld s七reng七hs of hoops used ar巴 shown in

Table 3. Me七hods of fabrication

，

curing of sp巴cimen

，

and measur巴men七 of strain were七he same as七hose of p工ain concre七e

トb

→

10 smH ぷ E l l 占円

H

U

H

U

H

U

円ハハ

U

b= 20.0 16.0 12.5 9.7 7.3cm

Fig.8 Size of confin色d concre七e specimen

自

己

;

1

b

2 b

。

一一

S

Fig.9 Arrangemen七of hoop

Table 2 De七ailes of confined concr巴七日 sp巴clrnens Size of pris盟 H

∞

p S告ctioll hE=h3bigh{tc圏} Dla且eter Spaclng bxb {c園) φ (臨}

"

。

7.3X 7.3 21，9 3.2 9.7x 9.7 29.1 3.9 b!4 b!2 12. 5X12. 5 37.5 4.9 15.0X15.

。

45

。

園

5. 7 b 00 20. OX20. 0 品0.0 8.0

(6)

小池狭千朗a畑中重光

(2) Strain at maximum 巴ompressive日七ress

Figure 11 shows七h巴 eff巴 C七 of

specimen size on 七he s七rain ( E m) a七

maximum compressive s七ress of 七he confined巴oncre七e for various spacing of

hoops. 1七 i日 shown七ha七， for plain con巴r己七e (S=∞) and confined concr巴七日 w工七h large spacing (S=b) of hoops，七he value of E m is hardly affected by 七he sp巴巴imen

size for b>9.7cm. For confined

巴oncre七e wi七h small spacing (S=b/4

，

b/2)

of hoops， however，七he value of E m decreas巴s almos七 cons七anもly wi七h increasing size of specimen.

(3) Str巴ss-s七rain curve

Figures 12(a) 七o 12(d) show七he effe口七 of specimen size on the σ-E curve of confined concre七e for various spacings of hoops. Here

，

damage of concre七e men七ioned in Sec七ion 2.1. Thes巴

specimens

，

18re loaded under七he cons七an七 B七ra工n ra七e of abou七2x10-3/min. up to the specifi巴d s七rain (E =1 5x1 0-3)工n general.

(1) Compr巴ssive stre昭七h

Figur日 10 shows 七he巴ffec七 of

spe巴工men siz日 on the compressive s七rength

of confined con口r巴七e for variou日 spacing

of hoops・ I七is shown七hat

，

for plain concre七e (S=∞) and coぱ ined concre七日 wi七h large spacing (S=b) of hoops

，

the compressive s七reng七h incr巴ases wi七h increasing s工ze of specimen

，

which is

similar 七巴ndency observed for 七he plain concre七e工n Chap. 2. Such size effec七，

how巴ver， is not r巴cogniz巴d for 七he confined concre七e wi七h small spacing

(S=b/4

，

b/2) of hoops.

3.2 Tes七r巴sul七s and discussion

168

Yield s七rength of hoop Diru官官terof Yield ₍_同_s_t_r_f_/_e_E 目d民h) h

∞

'P 1(悶) 3.2 2415 3.9 2お8 4.9 1937 日.7 2983 8.0 2品54 Table 3

P

r i sm W/C=55% 合一一切S=b/4 企ー--8S = b / 2 Eーー一白S二b ⑩ 一一憩 S=∞

よ︺

凶 ↓

ヒ立、人↑

也

、

京

、ふ﹂廿， F

A

¥

口町ぽ 3.5

g

ω ;- 3.0 0 M X 2.5

Z

ト寸 ~ 2.0 E己ト ∞1.5 。一ーや S=b/4 bー込 S=b/2 日ーーイヨ S=b トー →

s

=

∞

A44 国 / 下〆止イ﹄，

十

基

・

₄

芽

n u n u n u n U 5 0 5 0 ﹃ J q J ワ︼つ ω ( 刊 EU¥ 刷出 v ごヱト O Z 同ぽト

ω

P r i sm W/C=55% 7.3 9.7 12.51 5.0 20.0 WIDTH(cm).b 1.0 20.0 7.3 9.7 12.51丘O 1ちO

Fig.11 S七rain(E m) a七maximum巴ompress工ve

s七ress of confined concre七e (prism) WIDTH (cm)， b

Fig.10 Compressive s七reng七h of confined concre七e (prism)

(7)

円 u n u n u n u 円 u n u n U ハ U 4 3 2 1 b h

一

N E U ¥ 同切さ ω ω 凶民ト ω 円 u n U 円 u n u 円 u n U ハ u n u λ ι τ q J 勺ムーム b J N W E υ ¥ 同国﹄一切切凶出ト ∞ 中心圧縮を受けるプレンおよびコンブアインドコンクリートの塑性変形挙動における寸法効果 169 m m m m m p ﹂戸 ι v p ﹂ n し p a 切っリウ t に d n u n U 79250 1 4 T A 円ム h u h u h U L u h u

。

6 8 10 12 円 U ハ u n U 円 U 円 U 円 u n u n U 4 3 2 1 b 二何日 υ ¥ 相切さ m m 同ぽト ω 7.3c m 2 4 STRAIN (XIO-3 )

，

εc (a) S=∞ 一一一一一一b= 7.3c m --b= 9.7c m 一一一一一b= 1 2.5c m -ー一一-一一一 b= 1 5.0c m ミ〉ト-~一一 o 一一 b=20.0 c m \でh 、~ "'-"-.~_-'-:: 0_-_ '- --...__、、ー三こ二、、ー ¥、司、、¥、ー、二ご、

----._ここ-こ

S=b/2 ~-.ーヘ

。

2 4 6 8 10 12

。

2 4 6 8 10 12 STRAIN (X10-3 )

，

εc STRAIN (X10-")， ec (b) S=b 円 U 円 u n u n u n u n u n u n U 4 ム q J 勺 L 1 L むよ N E υ ¥ 柏田﹄一 ω ω 凶凶ト ∞ 8 10 12 (c) s=b/2 4 6

。

2 STRAIN (X10-3 )

，

εc

Fig.12 Effec七of specimen size of s七ress-s七rain curve of confin巴d concre七e

(d) s=b/4 ハ U ハ U n u n u n u n U 4 3 2 b ，﹁巨 U ¥ 阿国﹄的

自

100

a

ト (/] 円 U 円 u n u n u n u n u A せ q J n 4 b n 一刊日

U

¥

柏田ぷ U】 ~ 100 出ト (/]

一

--S=b/il -ーーーー-S=b/2 ~-一~、ーも一一一一一S=b /-一一一一、とごケー-S=回 ~、\、--_ー~ー ¥ ¥ 、 ¥ 司、、、、、ー_{ー一}_{も、}_ー_、_句_、一-~匂ー←

一

n u n u n u n u n u 円 U バ ι z q J つムも二 N E U ¥ 柏田﹄ (/] ~ 100 出ト (/] b (/] ~ 100 出

←

(/] 一ーー一一S=b/4 ---S=b/2 ♂二ごて¥司一一一一一S=b k;--._一、¥ー ‘ 一一一S=∞ べ、

、

¥

"

、

9.7c m 、¥ 」『

。

2 4 6 8 10 12 ー

-

-一ーー-ーー、、 STRAIN (X10-3 )，εc (a) b=7.3cm 一一ー一一S=b/4 -ーー一一-S=b/2 一一ー一一S=b 一一- s =悶

。

2 4 6 8 10 12 ~ーヘ、ーー、、、、 ¥

い

へ

い

¥

¥ 、ー、‘_一一_、_ー_ー STRAIN (X10-3 )，εc (b) b=9.7cm 一一ー一一S=b/4 -ーーーーーS=b/2 一一一一一S=b 一一一ー一一S=回

--

→ー、

-

-。

2 4 6 8 10 12 STRAIN (X10-3 )，εc ¥、、一ーー一一ー一一一

一

F工g.13 Effec七of spacing of hoop on s七ress-s七rain curve of confined concre七e

(d) b=20.0cm

。

2 4 6 8 10 12 STRAIN (X10-")， ec (ロ) b=12.5cm

(8)

170 小池狭千朗・畑中重光

concen七ra七ed around七he mid-high七 of specimens， so 七ha七 a1工七he damage concentra七ed zones were within the s七rain measuremen七 region of specimens. The figures show七ha七七he descending por七ions of σ -E: curves become s七eeper wi七h increasing size of specimen regard1ess of

七he spacing of hoops.

Figures 13(a)七o 13(d) show七he effect of spacing of hoops on七heσ-E curve of confined concrete for various sizes of specimen. Fami1iar七endencyis observed七ha七七he compressive s七reng七h is higher and the descending por七ion of

σ-E: curve is 1巴ss s七eepfor七he sma11er

spacing of hoops. Note七ha七 this 七endency is more remarkab1e for七he sma11er specimens.

4. CONCLU810N

The effec七 of七he size of specimens

阻 d aggrega七es on the deforma七ionbehavior

of p1ain and巴onfined concre七es was

discussed. The fo11owing s七a七emen七日 can be drawn from七he s七udy.

1) For p1ain 巴oncrete

，

s七

ress(σ)-strain ( E) curves are qui七巴 differen七 be七ween microconcre七es in which七he maximum size of coarse aggrega七e is redu巴ed in propor七ion七o七he size of specimen. Name1y，七he compressive s七reng七h decreases and七he descending portion of a -E: curve shows more ducti1e behavior wi七h decreasing size of specimen or aggrega七e (Fig.7(a)七o 7(c)). Hence， it can be con巴1uded七ha七七he behavior of七he microconcrete may be more duc七i1e七han七he concre七e in ac七ua1 s七ruc七ura1memb巴rs.

2) The compressive s七reng七h of confined conロre七e increases wi七h in巴reasing size of

specimen for 1arge spacing of hoops. 8u巴h size effec七， however， is no七 recognized for sma11 spacing of hoops

(Fig.10) •

3) The beha vior of confined concre七e becomes more bri七七1e wi七h increasing size of specimen regard1ess of七he spacing of

hoops (Fig.12(a) to 12(d)).

REFERENCE8

1) AC1 Publica七ion 8P-24

，

Mode1s for Concre七e 8truc七ures

，

1970.

2) A1ami，Z.Y.， and Ferguson，P.M.， "Accuracy of Mode1s Used in Research on Reinforced Concre七e"

，

Journa1 of AC1

，

Proeedings Vo1.60， No.11， Nov ・1963， pp.1643-1664.

3) 8anga

，

C.M. and R.K.Dhir

，

"8七reng七h and Comp工ete 8tress-8七rain Re1a七ionships for Concre七e Tes七ed in Uniaxia1 Compression under Differen七 Tes七 Condi七ions"， Ma七eriaux e七Cons七ruc七ions，Vo1.5， No.30， 1972

，

pp.361-370.

4) Koike，8.， Okufuji，K. and Kobayashi，N.， "8ize Effec七 on 1ne1as七ic Deforma tion Behavior and Expression for 8七ress-8train Curves of Concre七e"，Cemen七Associa七ion of Japan

，

Review of七he 41 s七 Genera1 Mee七ing/ Technica1 8ession

，

1987

，

pp.244四

247.

ラ) Hughes

，

B.P. and G.P.Chapman

，

"The Deforma七ion of Concreもe and

Microconcre七e in Compression and Tension wi七h Par七icu1ar Reference七o Aggrega七e 8ize"

，

Magazine of Concre七e Research

，

Vo1.18， No.54， March 1966， pp.19-24.

6) Pons，G.， Ramoda，8.A. and Maso，J.C.， "1nf工uence of七he Loading His七ory on Fracture Mechani巴s Parame七ers of

Micro巴oncre七e: Effec七s of Low-Frequency

Cyc1ic Loading"

，

AC1 Ma七eria1 Journa1

，

No.85-M37， 8ep七.ーO巴七.1988， pp.341-346.

7) Gonnerman

，

H.F.

，

"Effect of 8ize and 8hape of Te百七 8pecimen on Compressive S七reng七h of Concre七e"， Proceedings of A8TM， Vo1.25， Part 11， 1925， pp.237-250.

8) Nevi11e

，

A.M.

，

"The Effec七of 810pe and 8ize of Concre七e Tes七 Cubes on Mean S七reng七h and 8七andardDevia七ion"，Magazむ1e of Concre七e Research， Vo1.8， No.23， Aug・

(9)

中心圧縮を受けるプレーンおよびコγファインドコンクリトの塑性変形挙動における寸法効果 171

9) Tanigawa

，

Y. and Yamada

，

K

，

・

"Size Effect in Compressive S七r巴ng七h of Concre七ell

，

C巴men七and Concre七e Research

，

Vol.8

，

1978

，

pp.181-190.

10) Mori七a

，

S.

，

Fujii

，

S. Ishizuka

，

H. 旦nd

Nakanishi

，

H.

，

"Size Effect in Model Test of Re工nforced Concre七巴 (Par七1. Size Effect in Model Con巴re七e"

，

Proceedings of

七he Annual Mee七ing of AIJ

，

1985

，

pp.477-478 工n Japan巴( B巴).