14.531~539(08-037).fm

Transcription

1 G Journal of the Korea Concrete Institute Vol. 20, No. 4, pp. 531~539, August, 2008 š x y w m š gj p { sƒ z 1) * 1) w w Evaluation of Flexural Strength for Normal and High Strength Concrete with Hooked Steel Fibers Young-Hun Oh 1) * 1) Dept. of Architecture, Konyang University, Nonsan , Korea ABSTRACT The purpose of this study is to investigate the mechanical properties of high strength concretes reinforced with hooked steel fiber. For this purpose, total 36 specimens whose variables are concrete compressive strength, steel fiber aspect ratio, and steel fiber volume contents, are made and tested. From the test results including previous research work, flexural performance of steel fiber reinforced high strength concrete is evaluated in terms of flexural strength and toughness index. Flexural behavior of steel fiber reinforced high strength concrete is enhanced with respect to the fiber volume content, the aspect ratio, and concrete compressive strength. More efforts are devoted to evaluate quantitatively between the flexural strength and the structural parameters such as the fiber volume content, the aspect ratio, and concrete compressive strength. Keywords : steel fiber concretes, flexural strength, toughness, fiber factor, energy dissipation capacity 1. gj p w ww, {w w ³ wš q p š. p gj pƒ š y w q w zw y š w. gj pƒ, ³ w p w y š. gj p w w p 1-6),, {, gj p, x, y gj p w p w w š w. 1,5,6) w m š gj p { sƒw» w x ww, w x» x ƒw gj p w { { p w. w» w { z sƒwš, w { wš w. *Corresponding author youngoh@konyang.ac.kr Received May 19, 2008, Revised June 26, Accepted July 25, by Korea Concrete Institute 2. x 2.1 x z x x gj p (30 50 MPa), x (62 72), y (1.0, %) x w, KS F 2566 JSCE-SF4 ( gj p { x ) w ƒƒ mm { x 3 w. gj p qk» w w, yw p,, n w 3 w n w 3 ywwš, w 5 ƒ yw w. y 2.0% ex w œ w w w. 2.2 x gj p msp p e 19 mm w ww. ü K S š x x Table 1 ùkù. x w 1,000 kn x» w 3 ƒ w š, d Fig. 1 ùkù d w. 531

2 Table 1 Properties of concrete and steel fiber W/C S/a Unit weight (kg/m 3 ) (MPa) (%) (%) W C S G Steel fiber Hooked end Length Diameter l f (mm) d f (mm) l f /d f Tensile strength (MPa) , ,060 Fig. 1 Setup for flexural strength test 3.1 q xk 3. x x q xk y w x w ³ w w w ³ s j x ¾ mw ³ w ƒ q š. ù y w x» {³ e ³ y y w x w ùkû, x ü ³e s ƒ w w w w z d ³ s f» w m q. 3.2 w - š Fig. 2 x w - š w š.» {³ w» ¾ w - š»» y y w w ùkùš, y ƒw w ƒw y w. wr x 72 y w x w - š x 62 w w w z w w š. w x ³ ƒw, gj p ¼ ƒ ƒ w. ³ ƒ Fig. 2 Load-displacement curves for specimens x ƒ f ù œw q w. 4. gj p { p 4.1 { w x gj p, x y ƒ š x w gj p { p e w w» w 4» ( 2), û 3), National Taiwan Univ. 4), Dahan Institute of Technology ) ww { 5) x Table 2 w š. gj p x z» 532 w gj pwz 20«4y (2008)

3 Table 2 Flexural strength of specimens Research group Specimen size (mm) Author Kwandong Univ. 2) f c (MPa) V l f /d f F 1 f r Eq. (1) Eq. (2) f f 28 (%) (=V f l f / d f ) (test) Prediction Test/pred. Prediction Test/pred Chungnam Univ. 3) Taiwan Univ. 4) Dahan Institute of Technology 5) Mean STD C.O.V - 26% - 27% ƒ j» w. Fig. 3 Table 2 ùkù gj p, y (V f ), x (l f /d f ), (F 1 = V f l f / d f ) { e w š. gj p, y, x ƒ f { ƒw ùkû, w { (R) gj p, y, x, w ƒƒ 87.5%, 77.8%, 81.0%, 85.7% ùkû. gj p, y, x ƒƒ gj p { š w š q. 4.2» { sƒ Wafa 6) Ashour gj p { sƒ w» w x ww, ¼ 60 mm, 0.8 mm, w 260 MPa w» 100 MPa x mm j» w. x y y (0%, 0.5%, 1.0%, 1.5% 2%), x k (1) { w. = V f» V f y (%). (1) š x y w m š gj p { sƒ 533

4 Fig. 3 Relationship between flexural strength and structural parameters Song 5) Hwang ¼ 35 mm, 0.55 mm š x w» 90 MPa x w. y 0%, 0.5%, 1.0%, 1.5%, 2% y g, x l (2) { w. 2 = V f V f (1) (2) w x { w (2) Table 2 ùkù, w d x Fig. 4 š. Wafa Ashour w { Fig. 4(a) ùkù x w d s³ 0.74 ( 26%) { sƒw š. wr Fig. 4(b) ùkù Song Hwang x w s³ 0.90, 27% yw { d š. ù gj p { Fig. Fig. 4 Prediction of flexural strength using proposed equation by previous researcher 534 w gj pwz 20«4y (2008)

5 3 gj p y x y w q. gj p { w w š w w v ƒ š q. 4.3 d sƒ» { y sƒw» w d sƒw. (3) w w š, ƒƒ d w s³ Fig. 4(c) Fig. 4(d) š. Error (%) Wafa Ashour { s³ 37.9% ùküš, Fig 4(c) d d š y w. w Song Hwang { s³ 15.3% ùkü yw d š d d ƒ.» { d y y w w sƒw, y w k w { w v. 5. š w { p sƒ 5.1 { sƒ = V predicted V test V test { gj p x ƒ { y q w t w - š sƒw w. Table 2 ùkù x JSCE-SF4 { w 28 x w { Table 3 š. w r Table 3 ASTM C1018 w w { wì ùkù. JSCE w { gj p, y, x, j ùkùš, ASTM w s jš ùkû. Fig. 5 JSCE w { š. JSCE w { g j p, y, x, w ƒƒ 80.9%, 74.7%, 65.6%, 82.9% ùkû. (3) Table 3 Flexural toughness index of specimens Research group Author Kwandong Univ. 1) Chungnam Univ. 2) Taiwan Univ. 5) Specimen ( -l f -V f ) 5.2 { Flexural toughness index ASTM C 1018 JSCE- I 5 I 10 I 20 I 30 SF gj p gj p, y, x ƒ { e w q w» w Fig. 6 { gj p { 7) w w 0.63 { w sƒw. gj p w gj p { ƒ j ùkù, y w w { w» w., gj p, y { ƒ j ùkùš. gj p» wš,» y ƒƒ w ù w w z { sƒw. w s š x y w m š gj p { sƒ 535

6 Fig. 5 Flexural toughness index calculated by the JSCE-SF4 method ƒ Fig. 6(e) Fig. 6(h)¾ ùkù, gj p y w ƒ yw š. p gj p w (F 1 ) { 93.4% ùk üš. gj p { gj p w xk l š w z x w { z dw q. š y x w s ww gj p z w xk { sƒƒ ƒ w š w. 5.3 gj p { gj p { sƒw» w» w { w, sƒw ù d { dw ùkû. w (1) (2) ù kù { gj p w w š w» d x w š w. gj p { w dw v ƒ, w { F 1 z x l w»» w gj p { w. = F 1 (4)» F 1 = l f / d f V f š, V f = y (%), l f / d f = x (aspect ratio) ùkü. (4) w { d k Fig. 7 { x w š. w x w d s³ 0.93, 12% yw d š. ù Fig. 7(b) d lƒ d sw y w. d { w v ƒ, d dw 25% (4) 0.75 g { w. = F 1 (5) w š gj p { dw Fig. 8 š., (5) gj p { y d yw dw ùkû. { x s³ 1.07, 13% dw š. w sƒw s³ 9% d { dw. Table 4 {» w { d l sƒw y t w š. (5) gj p { w gj p, y x (5) 536 w gj pwz 20«4y (2008)

7 Fig. 6 Increasement of flexural strength with various structural parameters w š w xk, y d { yw dw š q w. 6. š x w š gj p { sƒw» w x m ww,. 1) gj p { { j» gj p, y, x w w ùkùš, w z š w { p sƒw k w š q. 2) { { j» y e w gj p, y, j ùküš, š x y w m š gj p { sƒ 537

8 Fig. 7 Efficiency of the proposed Eq. (4) Fig. 8 Validation of the proposed Eq. (5) x z š. 3) y w { x { gj p w { w, w { gj p ùkü ƒ ƒ j ùkù š. gj p { w w sƒw w š q. 4) w { gj p w { ƒw gj p gj p, y x w š w gj p w w w xk. { s³ 1.07, 13%, s ³ 9% { dw š,» { y d š. = F 1 (MPa) 2006 w w w (KRF D00697) Table 4 Comparison between flexural strength prediction methods Investigator Mean S. D. Median py g ( ) x w,. š x C.O.V. (%) Mean error (%) Wafa and Ashour 6) Song and Hwang 5) Proposed Eq.(5) xy, y, y š w SFRC x p, gj pwz, 16«, 6y, 2004, pp.759~ x, ½, š gj p p {, w wz, 24«, 2y, 2004, pp.455~ ,, š gj p w p» x p w x, wm wz, 26«, 2Ay, 2006, pp.401~ Jeng, F., Lin, M. L., and Yuan, S. C., Performance of Toughness Indices for Steel Fiber Reinforced Shotcrete, Tunnelling and Underground Space Technology, Vol. 17, 2002, pp.69~ w gj pwz 20«4y (2008)

9 5. Song, P. S. and Hwang, S., Mechanical Properties of High- Strength Steel Fiber-Reinforced Concrete, Construction and Building Materials, Vol.18, 2004, pp.669~ Wafa, F. F. and Ashour, S. A., Mechanical Properties of High-Strength Fiber Reinforced Concrete, ACI Materials Journal, Vol. 89, No. 5, 1992, pp.449~ ACI Committee 318, Building Code Requirements for Reinforced Concrete, American Concrete Institute, 2002, 443 pp. š gj p { { sƒw» w x ww, w x» x ƒw š gj p { p w. š gj p { p sƒw, w p gj p, y x, w w q.» w { z sƒw, gj p { gj p, y x, w š w sƒw w š q. y { w w { w. w : gj p, {,,, š x y w m š gj p { sƒ 539