NONLINEAR ANALYSIS OF CARBON FIBER SHEET CONFINED CONCRETE COLUMNS

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1 22 Vol.22 No ENGINEERING MECHANICS Feb (2005) * ( 00084) (CFS) (M-φ) (P-) CFS 8 CFS P- CFS CFS (CFS) TU38 A NONLINEAR ANALYSIS OF CARBON FIBER SHEET CONFINED CONCRETE COLUMNS LI Jing, * QIAN Jia-ru (Tsinghua University, Beijing 00084, China) Abstract: With gradual increase of curvature and step-by-step numerical integration method, the section moment-curvature (M-φ) relationship curve of carbon fiber sheet (CFS) confined concrete column as well as the lateral force - top displacement (P-) curve of CFS confined concrete column subjected to monotonic increasing lateral load are obtained. A computer program is developed to perform full-range nonlinear analysis of CFS confined concrete columns subjected to monotonic increasing lateral load. The calculated P-curves of 8 CFS confined concrete column specimens and unconfined concrete column specimen are in good agreement with the experimental results. The influence of confinement degree of CFS and the axial load ratio on the post-yield deformation capacity of the CFS confined concrete column is investigated. Key words: carbon fiber sheet (CFS); reinforced concrete column; CFS confinement degree; axial force ratio; deformation capacity (CFS) [~6] CFS CFS CFS ( ) (977) ( ) * (946) ( qianjr@mail.tsinghua.edu.cn)

2 ( 0 ) > 0 β = (6) 0.308( 0 ) 0 ε / ε = + 2. λ (7). (3)(4)(7) f c0 ε c0 ε cu f y ε y ε s,h E s E s CFS 0.0 E s f FS = ρ FS (8) f c0 σ ρ CFS f CFS f y Es εy εs,h Es' ε.2 Fig. Stress-strain relation curve of reinforcement CFS CFS (M-φ) [7] CFS [8] CFS 3 (2) ) ϕ 2) yi ε c,i = ϕ( R y i ) R 3) (2) 3 2 4) N σ da () x 2 CFS n h h M = N i ( R yi ) + N s ( a ) + N s ( a) Fig.2 Stress-strain relation curve of CFS confined concrete i= 2 2 ax x : y = () 2 + ( a 2) x + x As' εc' 0 x > : y = β ( x ) + (2) ε σ x =, y = σ ε CFS ε cc f cc f ε CFS cc cc f ε aβ cc cc ε ccu cc f c0 = FS ε cc/ ε c f / λ (3) = (4) a = 2 (.55 + ) (5) FS ccu cu 60 FS λ λ < FS0 = 0 FS 0 FS FS 0 λ > 2,2,3 0 λ FS0.68(0.9 np ) 0.9 ab = 0 λ (9) n p CFS λab σ c,i i = c,i c,i N s = Asσ s N s = A s σ s N = N + σ A + σ h/2 dac,i As b i y i s s εs' εc,i s As φ y R 3 Fig.3 Coordinate system, strip elements and strain M distribution of the column cross section εs

3 6 n a a n ) CFS ε c ε ccu 4 CFS t.3 n CFS mm CFS δ = l M ( x) φ( x)dx (0) 5 mm 0 4Φ6 δ l φ(x) φ6-00 x m m+ φ 0 ~ φ m M (x) [9] l l p0 l p 4 P p0 5 ( : mm) M-φ Fig.5 Dimensions and reinforcement of specimens (Unit:mm) lp P l φy Fig.4 φu lp P lp0 l φy 4 φu Treatment of plastic hinge zone 3 P- ) P 85%2) ε 2 ε 3) θ ( ccu ) /20 u 2 φ c 00mm 0.8 CFS t 0.mm f FS MPa EFS 2 8 CFS 24GPa ε u CFS t mm 4 Table Parameters of specimens 2φ6 φ6-00 2φ6 n t f c/mpa YW YW YW YW YW YL YL YL YL mm

4 62 CFS P δ 6 P δ P δ 2 [0] 2 Table 2 Comparison of nonlinear analysis results, test results (a) YW-0 (c) YW-2 (e) YW-4 (g) YL-2 (b) YW- (d) YW-3 (f) YL- (h) YL-3 (i) YL-4 CFS ( ) 6 P mm Fig.6 Comparison of the nonlinear analysis results and the test results of P-curves of specimens and code formula results P u/kn u ì δ YW % YW % YW % YW % YW % YL % YL % YL % YL % P u u µ δ 0.7 CFS ) CFS 2) CFS CFS 3) CFS YW CFS 4) CFS CFS CFS 3 CFS P-δ C35 0.4% 0.8%

5 63 600mmCFS n n t n P /kn =0.66 =0.44 =0.66 =0.22 =0.44 =0 =0.22 λ FS =0 P /kn (a) n=0.6 =0.66 =0.44 =0.22 =0 P /kn (b) n=0.7 =0.66 =0.44 =0.22 =0 (c) n=0.8 (d) n =0.9 CFS 7 P-δ Fig.7 Influence of on P-δ curve of column under () different axial force ratio CFS 7 n P-δ (2) CFS - µ δ -θ u 7 8 ) (3) CFS CFS 2) CFS (4) CFS 3) CFS (5) n µ δ 4 n CFS µ δ 44) ( ) n µ δ (a) λ µ δ θu λ θ FS (b) FS u 8 θ u Fig.8 Influence of on target displacement ductility µ δ and target drift ratio θ u under different axial force ratio 4 µ δ ( 99 )

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