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1 Journal of the Korea Concrete Institute Vol. 24, No. 1, pp. 079~086, February, 2012 GGGGG 섬유보강콘크리트에묻힌 GFRP 보강근의부착거동에대한섬유영향평가 1) Á½ 1) Á 2) Á 1) * 1) ³ w y lœw 2) w» Influence Evaluation of Fiber on the Bond Behavior of GFRP Bars Embedded in Fiber Reinforced Concrete Ji-Eun Kang, 1) Byoung-Ill Kim, 1) Ji-Sun Park, 2) and Jung-Yoon Lee 1) * 1) Dept. of Civil and Environmental System Engineering, Sungkyunkwan University, Suwon , Korea 2) Korea Institute of Construction Technology, Goyang , Korea ABSTRACT Though steel reinforcing bars are the most widely used tensile reinforcement, corrosion problems are encountered due to the exposure to aggressive environments. As an alternative material to steel, the fiber reinforced polymers have been used as reinforcement in concrete structures. However, bond strength of FRP rebar is relatively low compared to steel rebar. It has been reported that fibers in matrix can resist crack growth, propagation and finally result in an increase of toughness. In this study, high-strength concrete reinforced with structural fibers was produced to enhance interfacial bond behavior between FRP rebar and concrete matrix. The interfacial bond-behaviors were investigated from a direct pullout test. The test variables were surface conditions of GFRP bars and fiber types. Total of 54 pullout specimens with three different types of bars were cast for bond strength tests. The bond strength-slip responses and resistance of the bond failure were evaluated. The test results showed that the bond strength and toughness increased according to the increased fiber volume. Keywords : pull-out test, fiber reinforced concrete, fiber reinforced polymer, bond strength 1. gj p w w ü w ƒ š. w w» w wù FRP (fiber reinforced polymer rebar), {,,, w ƒ w š.» FRP w w š. 1,2) ù FRP t xk š» w ùký. 3,4), ù š x w ùkü, t ñ ù, FRP x w û ùkü. *Corresponding author jylee@skku.ac.kr Received November 12, 2011, Revised December 24, 2011, Accepted January 3, by Korea Concrete Institute FRP w» w ww sƒ v w. w FRP sƒw. w g j p ƒ ƒwš, ü w. w 5) w ƒ z gj p 6) Neven w 7) š, Issa FRP gj p w { sƒw y j z ƒ w. Won 8) FRP w sƒ x mw PVA ƒ y gj p» t w FRP sƒw. gj p w FRP sƒƒ š FRP t x w w sƒƒ v w, w FRP w ƒ v w. 3ƒ 79

2 (, PVA, PP ) w gj p 2 FRP ( x ù x) t x sƒw x z sƒw» w Fig. 1 3ƒ. x FRP sƒw» w ü I t w. FRP œ x GFRP (glass fiber reinforced polymer bars). GFRP x t š sƒw» x w. ù x x FRP w. GFRP e ù A x GFRP (sand coating GFRP bars) H ù x GFRP (herically raping GFRP bars) w. x Fig. 1(b) x t w, ù x Fig. 1(c) Õ t x ƒ x w. p Table 1 w. gj p w» w œ PP, PVA w. Table 2 ùkü zjƒ (hooked type) w. w Table 2 Properties of structure fibers Fiber Hookend steel fiber PP (Polypropylene) PVA (Polyvinyl alcohol) Length (mm) Diameter (mm) Tensile strength (MPa) Elastic modulus (GPa) S gj p w w j» w t šx w PP, e t w yw w k PVA w. x p Table 2 ùkü. 2.2 w y w gj p GFRP sƒw» w w g j p ww (Table 3 ). gj p 1 msp pƒ, ƒ. w s e š ƒ. gj p y ƒƒ 0%, 0.5%, 1.0% 3 w. gj p yw q, š 1 w z v w 1/2 w w š 1 yww. z p û š 2 yww, š ƒwš 1 Table 3 Mix proportion of concrete Fig. 1 FRP bars Table 1 Material property of rebars Bar type Fiber Diameter (mm) Area (mm 2 ) Tensile strength (MPa) Elastic modulus (GPa) Steel GFRP-SC E-glass GFRP-HW E-glass Mix type W/B (%) Unit materials contents (kg/m 3 ) C W Coarse. agg Fine. agg HWA Fiber Plain Steel PP PVA HWA : high water reducing admixture w gj pwz 24«1y (2012)

3 Table 4 Test specimens Bars Steel GFRP-SC GFRP-HW Volume fraction of fiber 0% 0.5% 1.0% Steel fiber S-PC-1,2,3 S-ST0.5-1,2,3 S-ST1.0-1,2,3 PP S-PC-1,2,3 S-PP0.5-1,2,3 S-PP1.0-1,2,3 PVA S-PC-1,2,3 S-PVA0.5-1,2,3 S-PVA1.0-1,2,3 Steel fiber SC-PC-1,2,3 SC-ST0.5-1,2,3 SC-ST1.0-1,2,3 PP SC-PC-1,2,3 SC-PP0.5-1,2,3 SC-PP1.0-1,2,3 PVA SC-PC-1,2,3 SC-PVA0.5-1,2,3 SC-PVA1.0-1,2,3 Steel fiber HW-PC-1,2,3 HW-ST0.5-1,2,3 HW-ST1.0-1,2,3 PP HW-PC-1,2,3 HW-PP0.5-1,2,3 HW-PP1.0-1,2,3 PVA HW-PC-1,2,3 HW-PVA0.5-1,2,3 HW-PVA1.0-1,2,3 ƒ yww x w. x x sw Table 4 84 w. x gj p š wš 3ƒ ( x, x GFRP, ù x GFRP ) 3 gj p y (, PP, PVA ) y w. x gj p r š w 3 w. Table 4 t x S, SC x FRP, HW ù x FRP, ST ùkü. 3.1 x 3. x d w mm x œ ƒƒ 3 w, 24» w z kxw 28 w. x KS F 2405» 2,000 kn x» w 0.2 MPa w d w. x Fig. 2 ùkü. x» x û y w w gj p w j» y w w w y j. 10) 3.2 x y w gj p GFRP sƒw» w x ww. x y GFRP sƒwš w. x Fig mm x gj p gj p ü GFRP s w k w w. GFRP ¼ w ƒ gj p ƒw w» w» x xk w 5 w. x w ƒ q w k ƒ, 5 w e š ö x w. 10) ƒƒ 3 x w, ü 24» w z kxw 28 w. x 2,000 kn x» w ƒ w, d w LVDT x w ew. x x x Figs. 3, 4. Fig. 2 Compressive strength of fiber reinforced concrete Fig. 3 Bond test specimens gj p GFRP w w sƒ 81

4 Fig. 4 Bond test set-up 4.1 q xk 4. x š gj p m gj p w j w. x gj p j q ƒ w, ù x w q ƒ w q ƒ w ù v w ˆ q ƒ w. x q xk q ˆq ù. x q ƒ w, ù x q ˆq ƒ w ù, v q ƒ ù q ƒ w. 4.2 w ñ š y gj p GFRP w ñ Fig. 5 ùkü. w ñ 3 x t ùkü x w ñ Table 5 ùkü. x w 3ƒ w. FRP gj p t w» w w. ù w ƒw gj p ³ w w q w gj p q ƒ w Fig. 5 Load vs slip behavior of GFRP rebars in fiber reinforced concrete w ³ w w w q w ƒ k. x w x w x Fig. 5(a) PP ƒ 0.5% y 82 w gj pwz 24«1y (2012)

5 Table 5 Test results of bond stress - slip Specimens τ m s m τ r Specimens τ m s m τ r Specimens τ m s m τ r S-PC SC-PC HW-PC S-PC SC-PC HW-PC S-PC SC-PC HW-PC S-ST SC-ST HW-ST S-ST SC-ST HW-ST S-ST SC-ST HW-ST S-PP SC-PP HW-PP S-PP SC-PP HW-PP S-PP SC-PP HW-PP S-PVA SC-PVA HW-PVA S-PVA SC-PVA HW-PVA S-PVA SC-PVA HW-PVA S-ST SC-ST HW-ST S-ST SC-ST HW-ST S-ST SC-ST HW-ST S-PP SC-PP HW-PP S-PP SC-PP HW-PP S-PP SC-PP HW-PP S-PVA SC-PVA HW-PVA S-PVA SC-PVA HW-PVA S-PVA SC-PVA HW-PVA ƒ y» x w ƒw, w w z w. ƒ 1.0% y x ƒ 1.2% ƒw. PP y w x w ƒw w ƒ w. ƒ z ³ ƒ gj p wš, w ³ w» q. PVA PP y w w ùkþ. 0.5% PVA ƒ y q ƒ w» ¾ w w š, 1.0% PVA ƒ y w ƒ ƒ gj p ³ ƒ w g» q. w» d w x w. 11) x FRP w - ñ ƒ Fig. 5(b) t. w x FRP w - š w y ùkû. ñ 0.5 mm w w ùkùš ñ 12 mm w ùkù (» w» w, ñ 12 mm w z» w w ). ƒ ƒ» x (SC-PC) w» w w. ù ƒ z» w j ƒw.» x (SC-PC)» w ùkû, ƒ FRP z» w ùkù» w 1.5. w w w ñ ƒ ƒw. Fig. 5(b) SC-ST 1.0 SC-PVA 1.0 x» w w z w w ƒ ùkùš z w ƒw z» w wš. w x tv ƒ gj p û gj p q w q ƒ q w q ƒ û ù, ³ q ƒ ù š gj p w ƒ ƒw š. ù x FRP w - ñ ƒ Fig. 5(c) t. ƒ ù x FRP x FRP yw w z w ùkù. ƒ ù x FRP w - ñ ƒ gj p GFRP w w sƒ 83

6 x w - ñ w w ƒw., y ƒw w ³ z ƒ w e. 4.3 w w ñ x w FRP (1) w w Table 5 w. P τ max = πrL», τ =, P max = w, r = GFRP, L = ¼. w w 3 x w x 3 x s³ Fig. 6 t w. Fig. 6(a), x FRP, ù x FRP s³ w. x ù x FRP ƒw ƒw. x» x MPa, š x s v v, e PVA 1.0%ƒ y ƒƒ MPa. ù x FRP» x 24.3 MPa, šx s v v, e PVA 1.0%ƒ y ƒƒ MPa. x FRP ƒ 1.0% w s³ w. Fig. 5 w ñ w» w w z ƒ w wš mw x ³ w ƒ j w w w. šx PP t e w PVA 1.0% w w, PP ƒ PVA» ³ w z ƒ ù w ³ w PVA ƒ z ù kû. Fig. 6(b) ñ w. Fig. 6(b) ñ w ñ. y w w ñ w, y ñ j wš. ù x ù x ƒ y w ñ j ƒw. ñ w ƒ w (1) Fig. 6 Bond strength and slip of rebars in fiber reinforced concrete ù x ñ ( x HW-PC-1,2,3) 4.07 mm, x ñ ( x SC- PC-1, 2,3) 0.25 mm ù. ù ƒ sw x x w ñ j ƒw. 1.0% wš x ñ w ƒ j.» z ³ z w ƒ wì ñ ƒw» q. w ü ³ z ƒ z w ƒ ƒw š w ñ ƒw. 4.4 Fig. 7 ùkü. ñ 84 w gj pwz 24«1y (2012)

7 Fig. 7 Accumulated energy of rebars 10 mm w ¾ w - 2 mm w w, š ƒ x ùkü x. Fig. 7(a) w ƒ sw x ƒ sw» x (S-PC) w. Fig. 7(a) x y ƒw ƒw, p ƒ 1.0% x ƒ ƒw. Fig. 7(b) x FRP w ƒ sw x ƒ sw» x (SC-PC) w. Fig. 7(b) x FRP ƒ 0.5% ƒ ƒw. ù ƒ 1.0% sƒ w» x w. Fig. 5(b)» w w z w w ƒ ùkùš z w j ƒw». Fig. 7(c) ù x FRP w ùkü. ù x FRP» x w ù ƒw, p e PVA 1.0%ƒ w» x w z ùkþ. ƒ w w ƒ z. 5. y w gj p FRP x sƒw. x gj p GFRP,, y e w sƒ w. x mw w. 1) ƒ y FRP z ƒ. gj p PVA ƒ y FRP ƒ, t s v v z w. 2) PP» ³ z ƒ, PVA PP w z ³ z. ƒ z ù y w. 3) ƒ y FRP w ñ j ƒw. y ñ w, x ù x ƒ y w ñ j ƒw. 4) ƒ ûš ùkü gj p GFRP w w sƒ 85

8 x FRP y w. x FRP» w z ƒ ³ w ƒ w w w ƒw. 5) sƒ y ƒw ƒw, z >PVA > s v v 3ƒ y w z ƒ ùk û. zj w gj p ƒw» q w» w ( ) w ¾. š x 1. Micelli, F. and Nanni, A., Durability of FRP Rods for Concrete, Construction and Building Materials, Vol. 18, 2004, pp. 491~ Saafi, M., Effect of Fire on FRP Reinforced Concrete Members, Composite Structures, Vol. 58, 2002, pp. 11~ Davalos, J. F., Chen, Y., and Ray, I., Effect of FRP Bar Degradation on Interface Bond with High Strength Concrete, Cement and Concrete Composites, Vol. 30, No. 8, 2008, pp. 722~ Baena, M., Torres, L., Turon, A., and Barris, C., Experimental Study of Bond Behaviour between Concrete and FRP Bars Using a Pull-Out Test, Composites, Part B: Engineering, Vol. 40, No. 8, 2009, pp. 784~ Taylor, M., Lydon, F. D., and Barr, B. I. G., Toughness Measurements on Steel Fibre-Reinforced High Strength Concrete, Cement and Concrete Composites, Vol. 19, No. 4, 1997, pp. 329~ Neven, K. O., Watson, K. A., and LaFave, J. M., Effect of Increased Tensile Strength and Tougness on Reinforcing- Bar Bond Behavior, Cement and Concrete Composites, Vol. 16, No. 2, 1994, pp. 129~ Issa, M. S., Metwally, I. M., and Elzeny, S. M., Influence of FIbers on Flexural Behavior and Ductility of Concrete Beams Reinforced with GFRP Rebars, Engineering Structure, Vol. 33, 2011, pp. 1754~ », v,, t š gj p CFRP p, gj pwz, 21«, 3y, 2009, pp. 275~ ACI 440.1R-03, Guide for the Design and Construction of Concrete Reinforced with FRP Bars, ACI Commottee 440, 2003, 42 pp. 10.,,, w GFRP, w wz, 24«, 8y, 2008, pp. 93~ Bentur, A. and Mindess, S., Concrete Beams Reinforecd with Conventional Steel Bars and Steel Fibers: Properties in Static Loading, The Inernational Journal of Cement Composites and Lightweight Concrete, Vol. 5, No. 3, 1983, pp. 199~ x,, gj p w p w ¼ w, w œwz, 8«, 1y, 2008, pp. 43~488. gj p w FRP e z w. x 3, šx PP e PVA w w x w sƒw. x w gj p w e. ƒ z w w ³ w w ƒw ƒ ƒw, w ƒw. ƒ z >PVA >PP ùkû. w : x, gj p, s, 86 w gj pwz 24«1y (2012)