Effects of steel lap splice locations on strength and ductility of reinforced concrete columns

Abstract

Longitudinal steel lap splice is always required in reinforced concrete (RC) columns. Normally, in countries having high seismic risk, lap splices of longitudinal steel must be located around mid-height of the storey. However, in regions of low-medium seismic risk, including Hong Kong, lap splices of longitudinal steel begin right above the beam-column interface to facilitate ease of construction. Such splicing method would undesirably cause the column critical region to move away from the beam-column interface under inelastic deformation. In this paper, the effects of different lap splice locations of longitudinal steel on flexural strength and ductility of RC columns with concrete cube strength around 100 MPa are studied. Four RC column specimens, which contained no lap splice, all lap splices within and outside critical region, as well as lap splices in staggered manner, were tested under simultaneous compressive axial load and reversed cyclic inelastic displacement. It is evident from the results that the column containing lap splices within its critical region had the largest strength but the poorest ductility performance. On the contrary, the column containing lap splices outside its critical region had strength and ductility comparable to those of the column without lap splice. Based on these observations, a recommendation is proposed for positioning longitudinal steel lap splices in RC columns.