Steel-fibre high-strength concrete prisms confined by rectangular ties under concentric compression

Abstract

A B S T R A C TThis paper presents results from a continuing research program that aims to investigate the behaviour of highstrength concrete columns and to recommend some design procedures to Brazilian Building Code. The specific current work deals with experimental behaviour of steel fibre highstrength concrete columns (SFHSCC) confined with low ratios of rectangular ties under concentric compression. Twenty-four small-scale SFHSCC were tested under concentric loading and their behaviour were examined and compared with the behaviour of two normal-strength concrete columns. The variables studied in this work were the concrete strength, amount of transversal reinforcement and volumetric fraction of steel fibre. The results indicated that steel fibre not only improves the columns ductility, but also avoids the premature concrete cover spalling. Further, to improve the ductility of high-strength concrete column, the used amount of steel reinforcement is the same when tie confinement or steel fibre is applied. RI~SUMI~

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

“…The TR prediction equation [(Equation (2)] for HSC confined by transverse reinforcement is expressed in term of effective confinement index, T It , and was derived by regressing 69 experimental results obtained from compression tests on HSC columns with high strength transverse reinforcements [ 3 , 16 , 22 , 23 ], as shown in Figure 3 . The concrete compressive strengths and the transverse reinforcement yield strengths range from 53 to 124 MPa and 392 to 1000 MPa, respectively.…”

“…The relationship between fiber factor, , and is plotted in Figure 5 . Regression analysis was conducted on 27 experimental data of HSC column hybrids of transverse reinforcements and steel fibers [ 2 , 15 , 16 ] with concrete compression strengths from 68 to 200 MPa, yield strengths and transverse reinforcement volumetric ratios from 410 MPa to 856 MPa and 0.61% to 6.09%, respectively, and fiber volume fractions from 0.25% to 1.5%. The fiber factor, , is given in Equation (10).…”

“…The compression test results of HSC column hybrids of transverse reinforcement and steel fibers from Lima and Giongo [ 16 ], Paultre et al [ 2 ], and the authors (only test results from HSC columns with hybrid confinement) are used to verify the validation of Equation (11). Seventeen specimens with concrete compressive strength ranging from 65.1 MPa to 101.40 MPa, transverse reinforcement ratio varying between 0.61% and 7.29%, and fiber volume fractions ranging from 0.25% to 1.5% have been verified.…”

“…This is because steel fibers provide bridging action across microcracks in the matrix and improve resistance to crack opening due to the existence of the bond strength between the steel fibers and the matrix [ 1 ]. Several experimental studies have been undertaken to more fully understand the compressive behavior of HSC columns with hybrid confinement of hooked-end steel fibers and transverse reinforcement [ 2 , 7 , 14 , 15 , 16 ]. However, not enough works are available in the literature, apart from a research study by Paultre et al [ 2 ] who proposed an effective confinement index from the hybrid confinement of transverse reinforcement and steel fibers.…”

Confinement Reinforcement Design for Plain and Fibre Reinforced High Strength Concrete Columns

“…Hence, the design and detailing of critical hinge regions of HSC columns has been of great concern to engineers and designers in the recent past. This stalemate has recently been sought to be broken by exploring the possible application of fibrous concrete in HSC columns (Mansur et al, 1997, Campione et al, 1999, Foster and Attard, 2001, Lima Junior and Giongo, 2004, Sharma et al 2005. The concept of using a combination of suitable discrete and randomly oriented fibres with nominal amount of lateral steel has been mooted in the literature to ease the requirement of high amount of confinement in the hinge regions of HSC columns.…”