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Shear Behavior of RC むular Members
1 3 5 愛知工業大学研究報告 第 34号 B 平 成 1 1年 Shear B e h a v i o r o f RC 円形断面を有する u l a r Members む RC部材のせん断挙動 Hongxing免IU , KazuoYA l V L ADA, Y a s u z iSAKOU 同5t 共輿 t , 山 田 和 夫 +, 酒向靖二:j:t A b g t r a c t Thet h e o r yo fs h e a rb e h a v i o rf o rRCc i r c u l a rmembersproposedi nt h i s ,T hea g g r e g a t ei n t e r l o c ko f paperi sbasedont h ed i a g o n a lcompressionf i e l dt h e o r y c r a c k e ds e c t i o nandt h edowela c t i o no fl o n g i t u d i n a ls t e e la r ei g n o r e di nt h emodeL fs t i r r u ps t r a i ni sd i s c u s s e dandi ti sthoughtt h a t Thei n f l u e n c eo fnon~uniform o t h ei n f l . uence i sn e g l i g i b l e .Accordingt h e血 o d e l,t h es h e a rs t r e s ss h e a rs t r a i n r e l a t i o n s h i pf o rc i r c u l a r 血 embers can b ep r e d i c t e d . For a s c e n d i n g branch, p r e d i c t e dc u r v e sshowagooda g r e e血 e n twitht e s tc u r v e s .Forspecimenswithl i g h t 即 時s ,t h e r ei sd i f f e r e n c e between t h e o r e t i c a lc u r v e and t e s tc u r v ei n s t d e s c e n d i n gbranchThet h e o r yp r e d i c t st h a tt h ea n g l eo fd i a g o n a lc o血 p r e s s l o nw i l l varywiths h e a rs t r e s s .B e f o r et h ey i e l do fs t i r r u p,t h ei n c l i n e da n g l ew i l li n c r e a s e f 七e rt h es t i r r u phavey i e l d e d, Whilec o n c r e t e a ss t r e s si n c r e a s e ;andw i l ld e c r e a s ea s t r a i nhasreachedpeaks t r a i n ,t h ei n c l i n e da n g l e苛iVi l li n c r e a s eo n c ea g a i n .The s h e a rs t r e n g t he q u a t i o nproposedi nt h i spaperwhichi n c l u d e st h ee f f e c to f a x i a l 血 p l eformwhichi 8c o n v e n i e n tt ou s e,andi sc o n s i s t e n t f o r c ei se x p r e s s e di nas i withonewh i c hd o e sn o ti n c l u d ea x i a lf o r c e 岨 園 島 Keywo r : d s h e a rs t r e s s ;s h e a rs t r e n g t h ;a x i a lf o r c e s ;c r a c k s ;r e i n f o r c e dc o n c r e t e ; s t l r r u p s LI n t r o d u c t i o n 皿The s h e a rb e h a v i o ro fRC 血 e b e r si soneo fwhichr e s e a r c h e r sa r e v e r yi n t e r e s t e di n .A l thoughc o皿 p r e h e n s i v er e s e a r c h1),2) ont h i sf i e l dhas beenmadebymanys t u d e n t s,t od a t e v e r yl i t t l eworkhasbeenr e p o r t e don t h es h e a rb e h a v i o ro f RC c i r c u l a r I T c u l a rmembers a r e members Thec 血 no fb u i l d i n g useda sp i l e sandc o l u 笠I c e n g i n e e r i n g more and and t r a more e x t e n s i v e .I nt h i s paper t h e d i a g o n a lcompressionf i e l d t h e o r yi s ロ 圃 十 中国東南大学土木工学科(中国南京) I 愛知工業大学工学部建築学科(豊田市) 士十愛知工業大学大学院建設システム工学専攻 a p p l i e dt op r e d i c ts h e a rb e h a v i o ro fRC c i r c u l a rmembers. The d i a g o n a l comp r e s s i o nf i e l dt h e o r yi s proposed by 3 Wagner) i n 1929 t os t u d yt h ep o s t bucking s h e a r r e s i s t a n c e o f t h i n webbed metal bea 田 s .M i t c h e l l and l, 5 lh C o l l i n s4 add e v e l o p e dt h emodelsf o r s t r u c t u r a lc o n c r e t ei npuret o r s I o nand s h e a r by t h i st h e o r y . They assumed :t h ec o n c r e t e can t h a ta f t e rc r a c k i n口e r e s i s tnot e n s i o nandc o n c r e t ei nwebi s r e p l a c e d by a i d e a l i z e d d i a g o n a l compressionf i e l d . s a photographo ft h et e s t F i g,li s e c t i o no far e i n f o r c e dc o n c r e t ec i r c u l a r i c h i member t e s t e d i n s h e a ra t A I n s t i t u t e o fT e c h n o l o g y . Themag回 1 3 6 愛知工業大学研究報告,第 34号 B,平成 1 1年 , Vo l .34 ・ B, Mar.1999 n i t u d e so ft h ea p p l i e dl o a d sf o rt h i s member were a r r a n g e ds ot h a tt h e momentwasz e r oa tt h em i d p o i n to f t h et e s tr e g i o n . s i o ni nc o n c r e t e ; Rm= e f f e c t i v er a d i u s ,i s taken from o fc i r c u l a rs e c t i o n i n t e r n a ls i d eo fs t i r r u p s ; σ c = a v e r a g e c o n c r e t es t r e s si nd i a g o n a l c o m p r e s s i o nd i r e c t i o n . 級建務d F i g .1 C i r c u l a rs e c t i o nspecimen Wew i l lo n l yc o n s i d e rt h es e c t i o n 1 e x u r a lmoment wheret h ee f f e c t so ff and d i s t u r b a n c e so fp o i n tl o a d sa r e , t h ee f f e c t so f a x i a l n e g l i g i b l e .However l o a dw i l lb ed i s c u s s e df i n a l l y . Due t ot h ec r a c k sc o n s i d e r a b l e v a r i a t i o n s w i l l 'a r i s ei nt h el o c a l s t r a i n s ( h e n c es t r e s s e s )o famember. Rather than t r y i n gt o d e a lw i t h v a r i a b l el o c a ls t r a i n sands t r e s s e s, we w i l lc o n s i d e ro n l yt h ea v e r a g e s t r a i n s ands t r e s s e s . 2 .E q u i l i b r i u mC o n d i t i o n s C o n s i d e rt h ee q u i l i b r i u mr e q u i r e menti nv e r t i c a ld i r e c t i o nf o rt h ef r e e bodyshowni nF i g . 2 . I fwei g n o r et h ed o w e lf o r c eo ft h e ,a l lo ft h es h e a rf o r c e l o n g i t u d i n a ls t e e l a tt h es e c t i o nmustbecarηbyc o n c r e t e, t h a ti s r 1i 、、,, 、 、 盟 , , , E . Q=~sinα where Q=shear force;α=angle o f d i a g o n a lc o m p r e s s i o nt ol o n g i t u d i n a l s a x i so f member;ξ=πR;cosασc i r e s u l t a n tf o r c eo fd i a g o n a lc o m p r e s - G Fi g .2F o r c e si nf r e ebody R ; D e f i n i n g T=Q/7r a s nominal E q . ( l )becomes s h e a rs t r e s s .Thus, τ σc=_ : _. __ _ _. _ s 幻m α c o s α ( l a C o n s i d e r t h e e q u i l i b r i u m c o n d i t i o ni nv e r t i c a ld i r e c t i o nf o rt h e i n c l i n e d s e c t i o n shown i n F i g . 3 . ,wei g n o r et h edowelf o r c eo f S i m i l a r l y .F u r t h e r ,i ft h e t h el o n g i t u d i n a ls t e el a g g r e g a t ei n t e r l o c ko fc r a c k e ds e c t i o n i si g n o r e d ,a l lo ft h es h e a rf o r c ea tt h e s e c t i o n must b ec a 町 y b ys t i r r u p s . Because t h ed i r e c t i o no ff o r c ei n 宜e r e n tl o c a t i o ni s v a r i a b l e, t h e d i i n t e g r a li sn e e d e d . The s t i r r u p sa r e e q u i v a l e n t t o u n i f o r m s t r e s s e s, α w σs/x(αw=areao fs t i r r u p ;x = s p a c i n g = s t r e s so fs t i r r u p s ) . o fs t i r r u p s ; σ, Thus 皇 子 位 cosθ Q=2C; ( 2 ) I t i s n o t e dt h a tt h e e q u a t i o nf o r 1 3 7 ShearBehavioro fRCC i r c u l a rMembers i n t e r s e c t i n gl i n eo fc yl i n d e r and i n c l i n e dp l a n e, z=Rmc o t α s i n θ S u b s t i t u t i n gd z=R mc o t α ∞sedθintoE q . ( 2 ),by i n t e g r a l , oneo b t a i n s 固 assumptioni sshowni nF i g. 4 . 園 m α一α q叫一円﹂ 恒 一 σ τ一 W 2 一P 一 一 ( 2a ) ・ ぷ lぷ }内 aA叩lit--?L where Pw=2awI x R mi ss t i r r u pr a t i o . F i g . 4D i s t r i b u t i o no f s t i r r u ps t r e s s D e f i n i n gt h e r a t i o o fa v e r a g e s t r a i nt o maximum s t r a i ni nt h i s r e g i o na sn o n u n i f o r mf a c t o rK,t h a ti s K =BI8 t h u s, i n r e g i o n j , max' h_ K 8" 2K-l 2"1-K 8 1-K , . i=~[. . " _ _-!一一一一1 ,t h es t e e ls t r a i ni s belowt h ey i e l ds t r a i n 8 andt h es t e e l y, s t r a i n i n any l o c a t i o n 2 ( 1-K)x= -,2K-1= 8 .=一 一一一' 8 +一一一~ 8 .Byt h ef o l l o w i n g hK o r c e si ni n c l i n e ds e c t I on F i g .3F 3 .Average S t r e s s A v e r a g e R e l a t i o n s h i p s S出 血 Fort h es t e e li tw i l lb e assumed t h a tt h er e l a t i o n s h i pbetweent h el o c a l s t a i na tap a r t i c u l a rl o c a t i o n ,8,and t h el o c a ls t r e s sa tt h i ssamel o c a t i o n, sg i v e nby σ=Es8: : ;I y .Assomeo f σ,i t h es t e e ls t r a i na r e below t h ey i e l d h i l e some a r ea b o v e ( t h e s t r a i n ( 8 y) w s t e e ls t r a i ni so f t e nn o tu n i f o r m ),t h e r e l a t i o n s h i p between t h e a v e r a g e s t r a i nandt h ea v e r a g es t r e s sw i l ln o t beg i v e np r e c i s e l ybyt h i se q u a t i o n Assume s t e e ls t r a i ni n some a r e g i o n ,h,i sl i n e a rd i s t r i b u t i o n .T h i s 園 i n t e g r a l ,t h er e l a t i o n s h i pbetweent h e a v e r a g es t r a i nandt h ea v e r a g es t r e s s canb eo b t a i n e d . 手=~ [1εμ+f . 5 ' λ改] - r 4(1-K) ε K 1ε ε A σ=[ 一一一(_!)ー--ー(_! 2(1-K) ε (2K_ 1 ) 2 ( 3 ) ー -lzE 4K( 1-K) 令 。 Theu s i n gr e g i o nf o rEq( 3 )a r e8 max 三 8y 圃 and 8 一三E u . i,e.ksgE52K -E ーに, h u s . 1 T , 山 Y' - Y - -- t h er e l a t i o n s h i pbetweent h ea v e r a g e s t r a i nandt h ea v e r a g es t r e s scanb e e x p r e s s e dby 愛知工業大学研究報告,第 3 4号 B,平成 1 1年 , Vo l .3 4-B,Mar ,1 999 1 3 8 → フ).f EC= 1 . _ = 0 コ ε。=寸i a sc i : ! Jc ( E ,<KEy) σs=EsEs 1 E" K r E" 内 σ'"ト--ー(ーム)一一一ー=-(ーム , "2(1-K)'E, ' 4(1-K)'E, (2K_ 1 ) 2 一一一一一一J E , E , 4K(1-Kr' . σ,' "cyE , ( 3 a ) (KE ν豆E 三-E-Ev) y- ' " - 2K -1"Y ( E,〉一一一 >__~ν ι ι) ー 2K-] y 胆 o u n g ' s modulus o f where Es = Y s t i r r u p . For c o n v e n i e n c e, t h e a v e r a g e s t r a i nanda v e r a g es t r e s sa r el a b e l e d E" O'" r e s p e c t i v e l y .T h i sr e l a t i o n s h i pi s showni nF i g .5 . z h r I rム ︽ ;2yy K Thee f f e c t i v ei n d e xo fc o n c r e t et a k e c a r eo ft h es o f t e n i n gphenomenono f c o n c r e t ei nb i a x i a ls t r e s s e s .Basedon t h ea n a l y s i so f1 5 3s h e a r 七e s t so f i e l s e n and s i m p l e Tbeam, N B r a s e s t r u p6) found t h i sf a c t o r was e q u a l t o 0 . 7 2 . I t i s thought i n h a tt h i sf a c t o rr e l a t e s r e f e r e n c e s7) t r e l a t i v es h e a rs t i f f n e s so fs e c t i o n s .The r e l a t i v es h e a rs t i f f n e s so fs e c t i o n sw i l l i n c r e a s ea sl o n g i t u d i n a lr e i n f o r c e m e n t r a t i or I s eandd e c r e a s ea st h er a t i oo f s h e a r span t o depth r i s e . Based on r e g r e s s l o na n a l y s i so f178s h e a rt e s t s o f reinforcedωncrete Tbeams ( I h e f o l l o w i n g e m p i r i c a l beams), t e q u a t i o ni sp r o p o s e di nr e f e r e n c e s7). 旬 0. 15 β 0 . 5 λ=0 . 6 +一一一一一+一ι一一一 M/Q.d e s Ke 二てEy y 2K' ( 5 ) ( 0 . 5, ; : -M / Q. d, ; : -3 ,0 . 5三 s I, ; : -2 ) F i g .5S t r e s s s t r a i nr e J a t i o n s h i p0 1 s t i r r u p The s t r e s s s t r a i nr e l a t i o n s h i po f c o n c r e t ei nt h ed i r e c t i o no fd i a g o n a l c o m p r e s s i o ni sr e p r e s e n t e d by t h e f o l l o w i n ge q u a t i o n s . σ c=. i t fJ2主一(主) 2 ] " ' 0 " ' 0 1 0 ( 4 ) c= c y l i n d e rc o m p r e s s i o ns t r Where f v e r a g e comength o fc o n c r e t e ; Ec=a p r e s s i o ns t r a i no fc o n c r e t ei nd i a g o n a l = c o n c r e t e c o m p r e s s i o n d i r e c t i o n ; ε。 c o m p r e s s i o ns t r a i nc o r r e s p o n d i n gt o peak stress;λ= e f f e c t i v ei n d e xo f c o n c r e t es t r e n g t h . Takingv a l u eo fEo s h o u l da c c o r d withs t r e s s s t r a i nc u r v e . wh e r e s, =pJ , y /λ s t e e li n d e x . フ i sl o n g i t u d i n a l 4 Co盟 p a t i b i l i t yC o n d i t i o n 四 Ther e l a t i o n s h i pbetweenc o n c r e t e s t r a i n ,s t i r r u ps t r a i nands h e a rs t r a i n o fs e c t i o ncanbefoundedbyv i r t u a l work m e t h o d .A c t i n gap a i ro fu n i t v i r t u a lf o r c e on member shown i n F i g . 6 . I ti sn o t e dt h a tt h e r ea r ev i r t u a l s t r e s s e so n l yinψregion.Thev i r t u a l x p r e s s e dbyu s e s t r e s s e s σρσ,canbee o fE q . ( l a )andE q . ( 2 a ),r e s p e c t i v e l y . σ し l =一一一τ一 一 一 一 時 3mαcosα F 2 t a nα σ。 “^一一 π R ; p w ( 6 ) 1 3 9 ShearB e h a v i o ro fRCC i r c u l a rMembers Assumel o n g i t u d i n a ls t e e li sr i g i d , i . e .t h es t r a i no fl o n g i t u d i n a ls t e e li s i g n o r e d .I ti sn o t e dt h a tt h es t r e s s e s ands t r a i n so fc o n c r e t eands t i r r u pa r e n o tr e l a t e dt ol o c a t i o no fs e c t i o n s .By , o n eo b t a i n s v i r t u a lworke q u a t i o n J a. e 仲×刈1= = r σ 刈 命+ωx( ぞ G ω 山川 m ) ) μ X 叫 り♂ cE & _ 2 & _s i n α r=s i n α sα+3J(7) ム E q .( 8 )i st h ec o m p a t i b i l i t yc o n d i t i o no f c o n c r e t es t r a i nands t i r r u ps t r a i n . 5 .P r e d i c t i o no fShearBehavior Thee x p r e s s i o no fu l t i m a t es h e a r s t r e n g t hi sr e l a t e dt ot h eb a l a n c e d s t i r r u pi n d e xt h a tt h es t i r r u ps t a r t st o y i e l dandc o n c r e t er e a c h e si t su l t i m a t e c a p a c i t ya tp r e c i s e l yt h esamel o a d .By n t oE q .( 8 ), s u b s t i t u t i n gBc=ら Bs=Byi o n eo b t a i n st h ei n c l i n e da n g l eo f d i a g o n a l c o m p r e s s i o n o f b a l a n c e d s e c t i o ni nu l t i m a t es t a t e 伽 記 万 ( 8 a ) where ι =6y /60 • By s u b s t i t u t i n g t h e v a l u e o f α o b t a i n e d 仕om E q . (8-a) and C J ' c= } " f c 'σs= 1 ; 叩 i n t oE q . (l-a) and E q . ( 2・a )r e s p e c t i v e l y,o n eo b t a i n st h e f o l l o w i n ge q u a t i o nf o rb a l a n c e ds t i r r u p i n d e x : β λ b= 一 一 一 ( 9 ) l+Cb a ) . A c t u a ld i s p l a:盟主:Jenta nds 位話n 時 1 b ) α 2b- Vntualf o r 田 a nd結 国S F i g .6 A c t i n gapmro fu n i tば吋u a l f o r c eo nmember The i n c l i n e da n g l eo fd i a g o n a l c o m p r e s s i o nwoulda d j u s ti t s e l fs ot h a t t h es t r a i ne n e r g yi nt h esystemwould n t e r n a le n e r g y be minimized3). The i w i l lbeminimumi ft h ee x t e r n a lwork e n c ef o rag i v e nl o a d ,t h e done,andh e x t e r n a ld i s p l a c e m e n t ( i . e .s h e a rs t a i n ) where s W . b=b a l a n c e ds t i r r u pi n d e x . I fs t i r r u pi n d e xβw <βw.b ,s t i r r u p s w i l ly i e l db e f o r et h ebeamr e a c h e si t s u l t i m a t e s t a t e . By s u b s t i t u t i n g , C J ' s= f w y ' i n t oE q . (1・a ) and R=ゲ: E q . ( 2・a ) r e s p e c t i v e l y,t h ei n c l i n e d a n g l eo fd i a g o n a l c o m p r e s s i o ni n u l t i m a t e s t a t e i s g i v e n by t h e e x p r e s slOn i saminimum.T h i smeans生 =O.and dα' l e a d st o S i nα = A 一ES Ec-+c 一司,h 一S α m ( 8 ) ( 8b ) ・ By s u b s t i t u t i n g t h e v a l u e o f α )i n t oE q .( 1・a ) o b t a i n e dfromE q .( 8・b 1 4 0 愛知工業大学研究報告,第 34号 B,平成 1 1年 , Vo l .34 ・B , Mar.1999 and8 u b s t i t u t i n g5c=50' t h eu l t i m a t e s t r e n g t hcanb eo b t a i n e d I s w s λ=イ ず ( λー す) /1 ( 1 0 ) ' f u/ I fs t i r r u pi n d e x β'w>βw.b' s t i r r u p w i l ln o ty i e l di nu l t i m a t es t a t e .I ti s a p p r o x i m a t e l yt h o u g h tt h eu l t i m a t e s h e a r s t r e n g t h o f o v e r r e i n f o r c e d 8 e c t i o ni se q u a lt ot h eu l t i m a t es h e a r s t r e n g t ho ft h eb a l a n c e ds e c t i o n ,t h a t t a k i n g sW=s W . bi nE q .( 1 0 ) . i s, ComparingE q .( 1 0 )withu l t i m a t e s h e a rs t r e n g t hf o r Tゐeams7),i ti s found t h a tt h e sw/2 f o rc i r c u l a r o rT membersi sc o r r e s p o n dt o sw f beams. The e q u i l i b r i u mc o n d . i t i o n s,t h e , and t h e c o m p a t i b i l i t y c o n d i t i o n s t r e s s s t r a i nr e l a t i o n s h i p s havebeen o b t a i n e d , 8 0wea r enowa b l et omakea . i c t i o no fc i r c u l a rmemberl o a d e d p r ed i ns h e a r . Bys u b s t i t u t i n gE q .( 3a ),E q .( 4 ) i n t oE q .( 2 a ),E q .( 1・a ),r e s p e c t i v e l y , o n eo b t a i n s 1 2 )i ( 1 1 ) and( n c l u d e五 . v eunknowns, .Whens τand α h e a rs t r e s s 5" 50 Y, Ti t h e rf o u rcanbes i v e n t h eo sg , o l v e d . t r a i n canb h e a rs eo b t a i n e da 80 s s f o l l o w s . ; a l u ef o rτ a )8 e l e c tav b )Assumeav ; fα a l u eo c )C s i n gE a l c u l a t e 5c byu q .( 1 1 ) ; d )C s i n gE q .( 1 2 ) ; a l c u l a t e 5,byu e )C s i n gE q .( 8 ) ; a l c 叫叫eαbyu n g l ec a l c u l a t e dd o t ft h ea o e sn f )I i t ht h ee a g r e ew s t i m a t e da n g l e, s t i m a t eofαcouldb thenanewe e r e p e a t t h e s t e p madeand c )t os t e p e ) . g )C s i n gE q .( 7 ) . a l c u l a t e rbyu p p l yt h e o r y ti sn h et e c e s s a Toa ,i 巧r a c t o r λ. Because t h ef h e t o know t fRCc i r c u l a rmembersa e 8 t so r e s h e a rt o make r e g r e s s i o n n o t enough t q .( 5 )i a n a l y s i s, h e r eE su s e d . r e d i c t i o no fs The p h e a rb e h a v i o r f o r specimen L60・0 5( w h o s es e c t i o n r eg i v e ni p a r a m e t e r sa )i nT a b l e1 s r o v i d e s f o u r i g .7 nF . I showni tp ・ Y 8 . . K 8. 伺 0 . 0 2 rhnb ss t i r r u pi where sw=fwyPw/f n d e x . ci t r a i no fs Thes h e a rs e c t i o n si na c e r t a i n magnitude o fs h e a r can b e l .E q .( 7 ),( 8 ), p r e d i c t i o nbya b o v emode . Q 1 0 0 . 0 1 5 n c l i n e da n g l e S t r a i n,i fi .~ν _ ( 8,>一一~8v) 8.> 2K-1 y ヴ ' , (2K-li 、 一 一 一 一1 (K8,~8•, ~一一ーム) 2K-1 Y' 4K(I-Kr ' Y 0 . 0 0 5 n e m c''a e p r 7 五 aL ふ6 」一=こじニニニLト--ー(ー)一一--ー(ーι ) i n α 2( ' 4(1-K)'8, '( f c 28ys 1-K)'8, 1 2 ) τ一βwc o s α s i n a f c 2 1 S h a s r s t r a l n S t i r r u ps 位置'" 『合唱白 r c 円 a a , e b5 rnu 1 ・『 8L ('.(l尽日'R E g E f i • ! で つ smmtu 亙ωE l' 28 ysinα L岡田 ( 8 8.) ,く K " , f c nunununu ヱ=s竺竺ι BE42 (71siMCO 叩) コH¥hpmmωお 同 λ = f吟 一 QSpecimenL6 05 c u r v e s : s h e a r s t r e s s s h e a r s . t r a i n r e l a t i o n s h i p,s h e a rs t r e s s c o n c r e t es t r h e a rs a i nr e l a t i o n s h i p,s t r e s s s t i r r u p s t r a i nr e l a t i o n s h i p ands h e a rs t r e s s n g l er i n c l i n e da e l a t i o n s h i p .Thet e r m o i n to fc u r v e sc i n a lp o r r e s p o n da o n g i c o n c r e t es t r a i no f 0.0033λ.Thel ShearBehavioro fRCC i r c u l a rMembers 圃 r a t i o and n o n u n i f o r r nc o e 出c i e n t .I t can be s e e nt h a ti n f l u e n c eo fn o n uniformo fs t i r r u p sons h e a rb e h a v i o r i si n c o n s i d e r a b l e . Above F i g . 7d o e s n o t c o n s i d e r t h e n o n u n i f o r r n o f s t i r r u p s . i a lF o r c eonShear 6 .TheE f f e c to fAx S t r e n g t h h a ti ft h e r ei sa F i g 9 shows t c o r n p r e s s i o ns t r e s s σc i nd i a g o n a l ,i ti sn e c e s s a 可 t ohavecomd i r e c t i o n p r e s s i o ns t r e s s and s h e a rs t r e s s on . e .l o n g i t u d i n a ld i r e c v e r t i c a lp l a n e,i t i o n . For M o h r ' ss t r e s sc i r c l e,t h e magnitude o fl o n g i t u d i n a l compres s i o ns t r e s s,σ,, 1S 圃 圃 α 一 一泊 τ一n σ t u d i n a lc o o r d i n a t ei se x p r e s s e dm d i r n e n s i o n l e s sparameter ,/u '・ P r i o r t o s t i r r u p y i e l d, t h e r e l a t i o n s m p s between s h e a rs t r e s s and s h e a rs t r a i na r ea p p r o x i m a t e l y l i n e a r .Mtert h es t i r r u p shavey i e l d e d, t h e r ei samarkedd r o pi nt h es t i f fo f s p e c i m e n .Ass h e a rs t r e s shasr e a c h e d i t speaks t r e s s,t h e r ei sau n d u l a t ei n c u r v e s . The s a r n e phenomenon i s found i nt e s t s . As u l t i r n a t el o a di s r e a c h e d,t h en e e d l eo ft e s t machine r o c k s .I ti st h o u g h tt h a tt h epeaki s u n s t a b l e I tcanbes e e nfromF i g . 7t h a tt h e a n g l eo fd i a g o n a lc o m p r e s s i o nv a r i e s with s h e a r s t r e s s . The a n g l e o f d i a g o n a lc o r n p r e s s i o nw i l ldependon t h er a t i oo fs t i r r u ps t r a i nt oc o n c r e t e s t r a i n ( s e eE q .( 8 ) ) .B e f o r et h ey i e l do f s t i r r u p sフ b e c a u s e o f n o n l i n e a r o f h e i n c r e a s e i nc o n c r e t e c o n c r e t e,t s t r a i ni sg r e a t e rthans t i r r u p,s ot h e i n c l i n e da n g l ew i l li n c r e a s ea ss h e a r s t r e s si n c r e a s e .M terthes t i r r u p shave h es t i r r u ps t r e s sw i l lremain y i e l d e d,t a tac o n s t a n tv a l u e .FromE q .( 2 a ),i t canbeknownt h a ti no r d e rt oi n c r e a s e t h ea p p l i e ds h e a rt h ea n g l eo fd i a g o n a l c o m p r e s s i o nmustd e c r e a s e . 1 4 1 ( 1 3 ) E q .( 1 3 )canb ee x p r e s s e da s T=σ [ t a n α ) ( 1 3a 圃 よ ー1 ゆいハ コμ¥hwdωωLHFmL悶ωω 工 nunυnununununununU 1GURU7 ・auFDAoqunノ﹄ 1 4 0 悶 0" τ 4 ←tw 1 =1 . 2 % ム=0.81 FIg.9 U n I t eelementandMohr 旨 c i r c l e 卜 企-pw=1 . 2 弘k = l 1 ト*-pw=O.2 砧. = 0 . 8I ヒ ? てE盟 主 世lJ U m , 7i r 7 l n u n o 刀 r A 07 何事 印m u EM hd Fb o o E 0 . 0 0 5 0 . 0 1 0 . 0 1 5 0 . 0 2 0 . 0 2 5 S h e a rs t r a i n .y 剖 F i g .8showst h et h e o r e t i c a lc u r v eo f memberswhichhaved i f f e r e n ts t i r r u p Whilea x i a lc o m p r e s s i o nf o r c eN i s i l l a c t e dont h e rnember ,s t r e s s 0', w i n c r e a s e,andr e s u l t si nt h ev a r i a t i o n o fs h e a rs t r e s s . For s i m p l i c i t y ,I ti s assumedt h a tw h i l ea x i a lf o r c ei sa c t e d, t h ea n g l eo fd i a g o n a lc o m p r e s s i o nw i l l n o tvaη.Takingd i f f e r e n t i a t i o nt oE q . ), oneo b t a i n s ( 1 1a ・ 142 愛知工業大学研究報告,第 3 4号 B,平成 1 1年 , Vo l .34-B,Mar.1999 ムτ=tan凶 σl ( 1 3 b ) I ti 8n o t e dt h a tb e C a U 8 eo f a x i a lf o r c e, t h ei n c r e a s ei nl o n g i t u d i n a lc o m p r e s : i13,=N1 (n : R2+na, ), t h U 8 s i o ns t r e s 8i 81 andspecimenL90-10,r e s p e c t i v e l y .A t e s ts h e a rs t r a i ni sc a l c u l a t e d by d i v i d i n gt h emeasuredr e l a t i v es h e a r n tbyt h eg a g ed i s t a n c e .I n d i s p l a c e血 e t h i s t e s t, t h e g a g e d i s t a n c e s a r e 600mmand900mm,r e s p e c t i v e l y . 一G 一n 山 N一+ n V P 一 一π α ゲ し q品 ム ( 1 3c ) 副 SpecimenL 6 0 0 5 S u b 8 t i t u t i n gE q .( 8 b )i n t oE q .( 1 3 c ) andu s i n gE q .( 1 0 ), t h eu l t i 血 a t es h e a r s t r e n g t hwhichi n c l u d e 8t h ee f f e c to f a x i a lf o r c e1 8g i v e n I s w o s 211 1":(λー ':) (0 I sw( fO w¥, -~ 1 1 λ_s r_w)+ V2' 2' 2λ-βw ID D 斗 = ーと 庁一 J 百 f c F i g . 1 0Shears t r e s s s h e a rs t T . 出n c u r v e sf o rspecimenL60-05 Because swi smuchs m a l l e rthan 2 λ, a b o v ee q u a t i o ncanb ea p p r o x i m a t e l y e x p r e s s e da s I s w (1 s ーと毘 ( 1+斗) 1 1 r _ w (λ-~) f c ' J { c ' V N¥ ( 1 4 ) S問 c i m e nL 鉛ー1 0 ぞ0.12 f . > 0 . 1I u iOω ( / ) e0.06 ~0 . 0 4 ~O 位 話。 a e r a 一 一 α 礼 一月 M 一D 一n N 一ー十 N σ 一π 一 一 where 0 . 0 0 5 0β1 0 . 0 1 5 0 . 0 2 0 . 0 2 5 S h e a rs t r a i n,r o f l o n g i t u d i n a l s t e e l ; n= t h e r a t i o o f Y o u n g ' smodulu8o f8 t e e lt oc o n c r e t e . While σN =0,E q .( 1 4 )1 Ssamea sE q . ( 1 0 ) . 7 .Co 盟 p a r i s o nwithT e s t s E i g h t c i r c u l a r specimens a r e t e s t e d .Excepttwos p e c i m e n sw i t h o u t s t i r r u p,a t o t a lo f6 t e s ts p e c i m e n s whicha r e usedt ocomparewitht h e p r o p o s e dt h e o r ya r el i s t e di nT a b l e1 . Thetwos p e c i m e n so fthema r ea c t e d a x i a lc o m p r e s s i o nf o r c e . F i g .1 0 and F i g .1 1 show t h e r e l a t i o n s h i p s between s h e a rs t r e s s ands h e a rs t r a i nf o rspecimenL6005 ・ o0 . α l 50 . 0 1 0 . 0 1 50 .D . 20 . D . 2 5 S h e a r試問I n ,r F i g .11Shears t r e s s s h e a rs t r a i n ・1 0 c u r v e sf o rspecimenL90 tcanb e FromF i g .1 0andF i g .1 1,i s e e nt h a tt h ep r e d i c t e ds h e a rb e h a v i o r f o ra s c e n d i n g branch shows a g o o d agreement with t e s t .I t s h o u l dbe r e mentionedt h a tt h ed i a g o n a lc o担 p s s i o nf i e l dt h e o r yi sn o ti n t e n d e dおr t h e p r e d i c t i o n o fb e h a v i o r b e f o r e c r a c k i n g .T e s t si nF i g .1 0andF i g .1 1 show t h a t t h e specimens b e f o r e c r a c k i n g a r e s t i f f e r than t h o s e p r e d i c t e d .C o n t r a r i l y ,a f t e rc r a c k i n g t h es t i f fo ft h e o r e t i c a lc u r v ei sg r e a t e r thant e s tc u r v e ' so n e .T h i scanbee x p l - ShearB e h a v i o ro fRCC i r c u l a rMembers 一一ーー一ー ー ーー一ーー ー,ーー一--- - - ー一一ーー一ーー一ーーーーー,一一ー-ーー一 一一一一一一一一ーーーーーー-_一 1 4 3 ー - - - - - - - - ---~ヲ町ーー (u/fJc ( Z u/f j τ N o .S p e c i m e nD / Q DσN i a m e t e r M f c p, ん pw f 叩 (mm) ( M P a ) ( M P a ) (%) ( M P a ) M P a ) (%) ( L60・1 0 2L 6 0 0 5 3 0 0 3 0 0 1 .0 1 .0 。 。 。 。 4 2 6 0 . 2 4 9 3 2 6 . 8 5 4 . 9 2 4 2 6 2 6 . 8 5 4 . 9 2 0 . 4 4 9 3 0 . 0 9 1 0. 18 6 τ~/τ; 0 . 1 1 5 1 . 12 1 0 . 1 6 2 0 . 8 7 1 3L 6 0 0 5 F 4L 9 0 1 0 3 0 0 6 7 2 6 . 8 5 4 . 9 2 4 2 6 1 .0 54 0. 4 4 9 3 0 . 17 3 0 . 2 0 6 1 . 19 1 3 0 0 1 .5 2 6 . 8 5 4 . 9 2 4 2 6 0 . 2 4 9 3 0 . 10 2 0 . 1 1 2 1 .0 9 8 5 L90 ・ 0 5 3 0 0 1 .5 2 6 . 8 5 4 2 6 . 9 2 4 0. 4 4 9 3 0 . 12 0 0 . 1 5 6 1 . 30 6L 9 0 0 5 F 3 0 0 1 .5 0. 4 4 9 3 0. 16 6 0 . 2 0 1 1 .2 1 3I 圃 5 . 46 7 L_2 6.~ 4 . 9 2 4 2 6 N o t e :S u p e r s c r i p ttd e n o t e st e s tr e s u l t s ;s u p e r s c r i p tcd e n o t e sc a l c u l a t e dv a l u e s . a i n e dbyt h ef a c tt h a tt h es t r a i no f l o n g i t u d i n a ls t e e li s i g n o r e di nt h e . model There i s d . i f f e r e n c e between t h e o r e t i c a lc u r v e and t e s tc u r v ei n ,e s p e c i a l l y f o r d e s c e n d i n g branch 0 . The d e s c e n d i n g specimen L90・1 branch o fRC members i sp r o b a b l y n f 1 u e n c eo ft e s tc o n d i t i o n s s u b j e c tt oi and t h e peak i s u n s t a b l e . T h i s phenomenon i s much c l e a rf o rt h e . s p e c i m e n swithl i g h ts t e el T a b l e 1showst h a tt h ec a l c u l a t e d s h e a rs t r e n g t h sa r em o s t l yg r e a t e r thant h et e s tv a l u e s .Themeanv a l u e o ft h er a t i oo ft h ec a l c u l a t e ds h e a r s t r e n g t ht omeasureds h e a rs t r e n g t hi s 1 .1 3 2andt h ed e v i a t i o nc o e f f i c i e n ti s 0 . 1 2 9 .Ap r o b a b l ec a u s ei st h a tt h eE q . ( 5 ) which i s based on r e g r e s s i o n a n a l y s i so fs h e a rt e s t so fT-beamsand susedf o rd e t e r m i n i n g I b e a m s,andi f a c t o r λ d o e sn o tveηsuitt oc i r c u l a r members. mentwitht e s tc u r v e s .Ford e s c e n d i n g branch ,t h e r ei sd i 宜e r e n c e between t h e o r e t i c a l c u r v e and t e s t c u r v e, e s p e c i a l l yf o rspecimenwhichi sl i g h t l y tt h o u g h tt h a t r e i n f o r c e di ns t i r r u p .I t h ed e s c e n d i n gbrancho fRCmembers n f 1 u e n c e o f t e s t i s s u b j e c t t o i ,t h e c o n d i t i o n s . On t h eo t h e r hand l dt h e o r yhas d i a g o n a lc o m p r e s s i o n五e showedb e t t e ra c c u r a c yf o rs p e c i m e n s w i t h heavy s t i r r u p s than t h e ls 江 s p e c i m e n sw i t hl i g h ts t i r r u p s .Al s p e c i m e n si nt h i st e s t have l i g h t s t i r r u p s . A c c o r d i n gt ot h et h e o r y ,i ti s n f 1 u e n c eo fn o n showed t h a tt h ei u n i f o r mo fs t i r r u ps t r e s s on s h e a r b e h a v i o r i s i n c o n s i d e r a b l e . The g e n e r a l e l a s t i c p l a s t i c s t r e s s s t r a i n c u r v ef o rs t e e l can b e used a st h e r e l a t i o n s h i p between t h e a v e r a g e s t r e s sanda v e r a g es t r a i nf o rs t i r r u p . Thee q u a t i o nf o rs h e a rs t r e n g t ho f c i r c u l a rmembersi ss i m i l a rt ot h eo n e e a m s . The u l t i m a t e s h e a r o f Tb s t r e n g t ho fc i r c u l a r members w i t h s t i r r u pi n d e x sw i sc o r r e s p o n dt ot h e u l t i m a t es h e a rs t r e n g t ho fT-beams ' w/ 2 .T he s h e a r w i t hs t i r r u pi n d e xβ s t r e n g t he q u a t i o np r o p o s e di nt h i s p a p e rwhichi n c l u d e st h ee f f e c to f a x i a l f o r c ei sc o n s i s t e n twitho n ewhichd o e s a l n o ti n c l u d e a x i a lf o r c e .While砿 i o t ha r es a m e . f o r c ei se q u a lt oz e r o,b Thec a l c u l a t e ds h e a rs t r e n g t ha r e 嗣 8 .D i s c u s s i o nandC o n c l u s i o n s T h i s paper has f i r s t used t h e d i a g o n a lc o m p r e s s i o nf i e l dt h e o r yf o r t h eb e h a v i o ro fr e i n f o r c e dc o n c r e t e c i r c u l a r members m o n o t o n i c a l l y l o a d e di ns h e a r . Byp r o p o s e dmodel , t h e s h e a r s t r e s s s h e a r s t r a i n r e l a t i o n s h i pf o rc i r c u l a rmemberscan be p r e d i c t e d . For a s c e n d i n g branch, p r e d i c t e dc u r v e s showa g o o da g r e e - 愛知工業大学研究報告,第 3 4号 B,平成 11年, 1 4 4 m o s t l yg r e a t e rthant h et e s tV a l U e 8 . Thef a c t o rλforc i r c u l a rmembersi 8 p r o b a b l yd i f f e r e n tt oo n ef o rTbeams. The paper c o n t a i n s o n l y s i xt e s t s p e c i m e n st o compare with t h e o r y . More t e s t so fc i r c u l a rspecimens a r e r e q u i r e df o rd e t e r m i n i n gf a c t o r λ . V o l3 4 . B,Mar.1 9 9 9 目 如何 J ourna ,1 vol .7 1,p p .3 9 6 " ' I n s t i 408, Aug.,1 9 7 4 . 田 ιCollins, Michael P .,“Towards a R a t i o n a lTheoryf o rRCmembersi n Shear , "J ournaloft h eS t r u c t u r a l ,ASC , E Vol . 104,N o . 4, D i v i s i o n p p 6 4 9 " ' 6 6 6, A p r i l,1 9 7 8 . R e f e r e n c e s 6 .N i e l s e n,M. P .,andB r a e s t r u p M. 明. T, “ P l a s t i c Shear S t r e n g t h o f R e i n f o r c e d C o n c r e t e Beams, " B y g n i n g s s t a t i s k e Meddelese , r Copenhagen ,D enmark,V o l46,No3, p p .61" ' 9 9,1 9 7 5 . ヲ 1 .ACI-ASCE Committee 426, Shear S t r e n g t h o f R e i n f o r c e d 位r s ピ , "Journaloft h e C o n c r e t eMembe S t r u c t u r a lDi 杭 r " 悶 凶 と ヲ ' 1 5 幻 . 白 : l o 九 , n ASCE,Vo 1 .99, ST6,June,p p . 1 0 9 1" ' 1 1 8 7,1 9 7 3 . 2 .ASCEACICommittee445,“Recent Approaches t o Shear Design o f " J ournal of S t r u c t u r a lC o n c r e t e, S t r u c t u r a l Enginθe r i n , g Vol . 124, N o .1 2, p p .1375 " ' 1 4 1 7, December 1 9 9 8 . 圃 園 7 .. f r i [ 渋沢, J人;均引│特水中,“例筋粍什料栓 T形 被i i紫野切強度的IJ:¥ぬ研究, " ;JO;;今日)t~苦手壬!Ii 3 南京, ' [ 1同, V o 1 .2 3, No. 4 , p p .9 3~ 9 9, J u l y ,1 9 9 3 . 8 .酒向靖二,山田和夫,山本俊彦,浅井陽一,“場 所打ち鉄筋コンクリ一ト杭の実験(その 1せん断 3 .Wagner , H ., “ Ebene Blechwand t r a g e r mit s e h r dunnem S t e語 ; b l e c h 了Z e i t s c h r i 琵 f u r F l u g 宜a h r t t e c h n i k und M o t o r l u f t s c h i B e r l i n,Germany ,V o 1 .20,N o s .8・12, 1929. 4 .M i t c h e l l, D ., and C o l l i n s, M. P ., “ Diagonal Compression F i e l d Theory--A R a t i o n a l Model f o r S t r u c t u r a l C o n c r e t e i n Pure θ ,t e T o r s i o n , " American Concr 亨 実 ミ 恥 第 37号 , pp.289~292, 1 9 9 9 . 9 .1 量 益暢,二羽淳一郎"格子モデ、ノレによる RC はりのせん断性状の解析的評価"コンクグ一声 工学卒次瀞丈高官合案, ~568 , V o l .1 6,N o .2 ,p p .5 6 3 1 9 9 4 . 1 0 .二 羽 淳 一 郎 , 雀 益 暢 , 回 辺 忠 顕 " 鉄 筋 コ ン クリートはりのせん断耐荷機構に関する解析的研 究ぺ"土木学会最文集, 79~88 , No 5 0 8 八1 2 6, p p . 1 9 9 5 (受理平成 1 1年 3月 20日)