Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Steel fibres to improve structural performance of reinforced concrete members Ass. Prof. I. KOVÁCS University of Debrecen Hungary Prof. Gy. L. BALÁZS University of Technology and Economics Budapest Hungary 1
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Steel fibre reinforced concrete Aggregate Steel fibres Plain concrete Cement Steel fibre reinforced concrete 2
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Observations Tension Dl Compression Dl Increasing fibre content l Dl s Dl/l Increasing fibre content 3
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Observations Bending Increasing fibre content d d Effect of local force D D Increasing fibre content 4
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Use of SRC in a cross section Steel fibre reinforcement in concrete members Concrete ibre reinforced concrete Reinforcing bar Prestressing Steel fibre reinforcement in reinforced concrete and prestressed concrete members 5
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Use of SRC in a cross section Steel fibre reinforcement in repair and strengthening of concrete members Steel fibre reinforcement in the end block region of prestressed member 6
150 Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Series of reinforced concrete beams Reinforcing details 100 No stirrups 2 16 6/240 4/240 2 16 6/120 4/120 2 16 1800 mm 100 Hooked-end steel fibres 0 V% 0.5 V% 1.0 V% No stirrups A1 A2 A3 6/240 A4 A5 A6 6/120 A7 A8 A9 Crimped steel fibres 0 V% 0.5 V% 1.0 V% No stirrups B1 B2 B3 4/240 B4 B5 B6 4/120 B7 B8 B9 7
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD ailure loads and failure modes Hooked-end steel fibres Dramix ZC 30/.5 Crimped steel fibres D&D ~ 30/.5 A1 SHEAR AILURE u =24.2kN f c,cube = 37.58 MPa NO IBRES NO STIRRUPS f sp,cyl = 1.57 MPa B1 SHEAR AILURE u =21.6kN NO IBRES NO STIRRUPS f c,cube = 42.70 MPa f sp,cyl = 1.60 MPa A2 SHEAR AILURE u =29.0kN f c,cube = 39.85 MPa 0.5 V% NO STIRRUPS f sp,cyl = 2.62 MPa B2 SHEAR AILURE 0.5 V% u =33.6kN NO STIRRUPS f c,cube = 48.80 MPa f sp,cyl = 2.81 MPa A3 SHEAR AILURE u =35.0kN f c,cube = 38.55 MPa 1.0 V% NO STIRRUPS f sp,cyl = 3.63 MPa B3 COMBINED AILURE u =44.7kN 1.0 V% NO STIRRUPS f c,cube = 47.16 MPa f sp,cyl = 4.13 MPa 8
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD ailure loads and failure modes Hooked-end steel fibres Dramix ZC 30/.5 Crimped steel fibres D&D ~ 30/.5 A4 SHEAR AILURE u =35.7kN f c,cube = 37.58 MPa NO IBRES 6/240 f sp,cyl = 1.57 MPa B4 SHEAR AILURE NO IBRES u =27.5kN 4/240 f c,cube = 42.70 MPa f sp,cyl = 1.60 MPa A5 SHEAR AILURE 0.5 V% u =35.1kN 6/240 f c,cube = 39.85 MPa f sp,cyl = 2.62 MPa B5 SHEAR AILURE u =44.3kN f c,cube = 48.80 MPa 0.5 V% 4/240 f sp,cyl = 2.81 MPa A6 BENDING AILURE u =35.0kN 1.0 V% 6/240 f c,cube = 38.55 MPa f sp,cyl = 3.63 MPa B6 BENDING AILURE u =45.7kN 1.0 V% 4/240 f c,cube = 47.16 MPa f sp,cyl = 4.13 MPa 9
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD ailure loads and failure modes Hooked-end steel fibres Dramix ZC 30/.5 Crimped steel fibres D&D ~ 30/.5 A7 BENDING AILURE NO IBRES u =37.4kN 6/120 f c,cube = 37.58 MPa f sp,cyl = 1.57 MPa B7 SHEAR AILURE NO IBRES u =35.2kN 4/120 f c,cube = 42.70 MPa f sp,cyl = 1.60 MPa A8 BENDING AILURE 0.5 V% u =35.0kN 6/120 f c,cube = 39.85 MPa f sp,cyl = 2.62 MPa B8 SHEAR AILURE u =46.6kN f c,cube = 48.80 MPa 0.5 V% 4/120 f sp,cyl = 2.81 MPa A9 BENDING AILURE u =36.6kN 1.0 V% 6/120 f c,cube = 38.55 MPa f sp,cyl = 3.63 MPa B9 BENDING AILURE u =45.0kN 1.0 V% 4/120 f c,cube = 47.16 MPa f sp,cyl = 4.13 MPa 10
w [mm] w [mm] Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Crack development B7 20kN - RC-B7-4/120-0V% D&D 30/.5 B9 20kN - RC-B9-4/120-1.0V% D&D 30/.5 0.20 0.16 0.12 n = 22, w = 1.450 mm w m = 0.066 mm, s m = 78 mm 0.20 0.16 0.12 n = 30, w = 1.030 mm w m = 0.034 mm, s m = 58 mm 0.08 0.08 0.04 0.04 0.00 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0.00 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Position of crack, x [mm] Position of crack, x [mm] 11
Crack width, w [mm] Crack width, w [mm] Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Crack development B7 B9 RC-B7-4/120-0 V% D&D 30/.5 RC-B9-4/120-1.0 V% D&D 30/.5 0.20 0.16 0.12 u = 35.2 kn f c = 42.7 MPa f sp = 1.60 MPa Shear failure 0.20 0.16 0.12 u = 45.0 kn f c = 47.16 MPa f sp = 4.13 MPa Bending failure 0.08 0.04 0.00 30 kn 0 kn 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0.08 0.04 0.00 0 200 400 600 30 kn 0 kn 800 100012001400160018002000 Position of crack, x [mm] Position of crack, x [mm] 12
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Proposal for crack spacing Plain concrete s rm 50 0. 25k1k2 r 0.5 V% steel fibre content s rm 45 0. 25k1k 2 r 1.0 V% steel fibre content s rm 40 0. 25k1k 2 r Crack width w k s rm sm 13
Mean crack spacing [mm] Mean crack width [mm] Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Crack spacing and crack width 100 90 80 70 EC2 (No steel fibres) 0.5 V% fibre content (Proposal) 1.0 V% fibre content (Proposal) No steel fibre (Measured) 0.5 V% steel fibre (Measured) 1.0 V% steel fibre (Measured) 0.16 0.14 0.12 0.10 EC2 (No steel fibres) 0.5 V% fibre content (Proposal) 1.0 V% fibre content (Proposal) No steel fibre (Measured) 0.5 V% steel fibre (Measured) 1.0 V% steel fibre (Measured) 60 0.08 50 0.06 40 0.04 30 0.02 20 0 5 10 15 20 25 30 35 orce, [kn] 0.00 0 5 10 15 20 25 30 35 orce, [kn] 14
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Conclusions ailure modes and failure loads 1) Steel fibre reinforcement can effectively be used to improve shear capacity of plain concrete in beams made with no stirrup reinforcement. 2) If reinforced concrete beams contain the required amount of conventional shear reinforcement, hence fail in bending, the addition of fibre does not considerably increase the failure load. 3) With sufficient amount of fibres the failure mode could be changed from shear failure to bending failure. 4) Steel fibres do not only increase shear capacity but also provide substantial post-peak resistance and ductility in conventional reinforced concrete members 15
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Conclusions Cracking behaviour 1. Steel fibres in concrete beams provide uniformly distributed cracks. 2. More cracks developed in beams containing steel fibres than in case of beams made of plain concrete and consequently smaller crack spacing was observed. 3. Significant reduction of average crack width was observed by the use of steel fibres. 4. Cracking characteristics was not significantly effected by the type of fibre. 5. A modification to the crack spacing formula by EC2 was developed in order to consider the effect of steel fibres. 16
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Structural application of model ARCHI STAT LTD. Architectural & Structural Design Bureau Nyiregyháza, Hungary Zsolt KASSAI DLA architect Imre KOVÁCS PhD structural engineer REE SHAPE SENDWICH SHELL HOUSES Egerszalók, HUNGARY Patented building technology for sendwich shells 17
Steelibres to Improve Structural Performance of Reinforced Concrete Members by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD Steel fibres to improve structural performance of reinforced concrete members THANK YOU OR YOUR KIND ATTENTION! Ass. Prof. I. KOVÁCS University of Debrecen Hungary Prof. Gy. L. BALÁZS University of Technology and Economics Budapest Hungary 18