Design of reinforced concrete frames of limited ductility.

Abstract

An experimental programme was carried out to investigate the flexural strength and ductility. of reinforced concrete columns under simulated earthquake loading. The main variable examined was the quantity of transverse reinforcement for concrete confinement. The experimental results were described and compared with theoretical studies. It was found that to achieve adequate ductility in columns, the current New Zealand concrete design code NZS3101:1982 equations for concrete confinement need to be refined. Using design charts for ductility, which were previously derived from a theory for cyclic moment-curvature behaviour, a refined design equation to replace the current code equations is proposed. The inelastic dynamic response of frames of limited ductility was examined, and compared with the response of ductile frames. The analysis indicated that non-capacity designed frames, designed for seismic forces corresponding to a limited ductility demand, performed reasonably well. Although some plastic hinges did develop in the columns, the ductility demand was acceptable and can be achieved by appropriate detailing. As a result, some suggestions for the seismic design requirements of frames of limited ductility are presented.