Quasi-static cyclic load performance of encased concrete-filled steel tubular with steel loops joint using sustainable concrete

Abstract

An extensive experimental investigation has been performed to understand the seismic behaviour of the beam-column joint when sustainable materials are used. The structural joint between the encased concrete-filled steel tubular (ECFST) column and reinforced concrete (RC) beam is the scope of the study and the sustainable concrete used in the experiments are made with the addition of fly-ash and steel fibres. In the typical connection studied in this investigation between the ECFST column and RC beam, a problem of continuity of the longitudinal reinforcement of the beam at the joints to the other side is encountered. This interruption is overcome by the provision of pre-fabricated steel loops in the joint. This study discusses about the seismic characteristics of the joints such as hysteresis behaviour, lateral load capacity, ductility, energy dissipation capacity, rigidity degradation and brittleness index when the steel loop is provided at the joint and the fly-ash and steel fibre are used in the concrete. Also, impact of the various numbers of rings in the steel loop assembly and the addition of fly-ash and steel fibre were studied to obtain the optimum combination to satisfy the seismic performance. The results indicate that the steel loops at the joints substantially increased the seismic performance of the ECFST column and RC beam joint which was also supported by the higher ductility and energy dissipation capacity due to the fly-ash and the steel fibre present in the concrete. Also the replacement of cement by fly-ash up to 10% in the concrete does not reduce the lateral load capacity and other seismic criteria which lead to lesser carbon di-oxide emission to the environment and utilization of industrial waste with no compromise in the performance.