Enhancing ductility of reinforced concrete frame buildings

Abstract

Two large-scale, two-storey subframes with non-seismic reinforcement detailing and limited seismic detailing were tested under quasi-static cyclic loading to investigate the seismic behaviour and ductility enhancement of reinforced concrete frame buildings for low-to-medium earthquakes. The inherent ductility of an ordinary moment-resisting reinforced concrete frame was experimentally established by testing the subframe specimen in the case where the reinforcement detailing is consistent with that typically adopted for frame buildings in which the design code has not stipulated any requirement for seismic compliance in the steel details. Experimental investigation was then performed on the other subframe specimen to investigate the enhancement to ductile response behaviour following modifications of the reinforcement detailing technique. The modifications were simple and included reducing the spacing between the stirrups while maintaining the ratio of the stirrup area to spacing; the provision of double-U stirrups at the beam–column joint and the addition of inclined bars within the beam at the support region. It is concluded that ordinary moment-resisting frame buildings might not withstand low-to-moderate seismic events. However, the ductility of frame buildings can be significantly improved with minor modification in reinforcement detailing specifications, which do not result in radical changes in currently practiced design and detailing techniques and a significant increase in construction cost.