High Strength Concrete Columns under Axial Compression Load: Hybrid Confinement Efficiency of High Strength Transverse Reinforcement and Steel Fibers

Abstract

Addition of steel fibers to high strength concrete (HSC) improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR) to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25–1 effective depth of the section column. Furthermore, the axial load–strain curves were developed by employing finite element software (OpenSees) for simulating the response of the structural system. Comparisons between numerical and experimental axial load–strain curves were carried out.

Cyclic Response of Steel Fiber Reinforced Concrete Slender Beams: An Experimental Study

“…SFRC under compression exhibits increased strength only in mixtures with a high amount and adequate aspect ratio of fibers, whereas it exhibits a rather marginal contribution of the fibers on the compressive strength in most of the examined cases [1,2,3,4,5,6]. Nevertheless, significant improvement of the post-cracking stress–strain compressive behavior with noticeable toughness and a ductile response even in low volumetric proportions of fibers has been revealed [7,8,9,10]. A significant increase in the SFRC compressive strength is achieved in mixtures with at least 3% volume fraction of steel fibers [11,12].…”

Shear Strength Prediction Equations and Experimental Study of High Strength Steel Fiber-Reinforced Concrete Beams with Different Shear Span-to-Depth Ratios

“…Swamy et al [27] set the bond strength between steel fibers and concrete matrix at 4.15 MPa. Liao et al [2] and Perceka et al [9] conducted single-fiber pullout tests to determine the equivalent bond strength that describes the bond strength of the fiber-matrix interface. In order to account for the equivalent bond strength, τ eq , Equation (1) that was proposed by Kim et al [2] can be used.…”

“…In order to account for the equivalent bond strength, τ eq , Equation (1) that was proposed by Kim et al [2] can be used. In addition, Liao et al [2] and Perceka et al [9] used micromechanical model proposed by Xu et al in 2011 [2,9] to verify the experimental results. Both authors reported that the difference between the experimental and analytical results was only 10% [2].…”

“…However, concrete becomes more brittle as its compressive strength increases and greater transverse reinforcement is required accordingly [2][3][4][5]. Short and discontinuous steel fiber can be used as an alternative material to improve the ductile behavior of concrete [2,[6][7][8][9]. Previous research studies have shown that adding steel fibers to concrete beams could enhance shear resistance, toughness, promote flexural failure and ductility, and potentially act as a substitute for conventional shear reinforcement [10][11][12][13][14][15][16][17].…”

“…Previous research studies have shown that adding steel fibers to concrete beams could enhance shear resistance, toughness, promote flexural failure and ductility, and potentially act as a substitute for conventional shear reinforcement [10][11][12][13][14][15][16][17]. In addition, the randomly oriented steel fibers provide bridging action across the microcracks in the matrix and improve resistance to crack opening [2,9,[18][19][20]. The shear stress on the interface between the steel fibers and the surrounding matrix (bond strength between steel fibers and matrix) is a key parameter in the bridging role and in providing more tensile strength during fracturing.…”