Performance of reinforced concrete frames using force and displacement based seismic assessment methods

This paper reviews the traditional force-based (FB) seismic design method and the newly proposed displacement-based (DB) seismic assessment approach. A case study is presented for reinforced concrete (RC) moment-resisting frames designed and detailed according to European and Australian earthquake code provisions, having low, medium and high ductility capacity. The aim is to assess the performance characteristics of these frames, using the well known El Centro NS earthquake ground motion as the seismic input. Overall ductility demands have been computed for the force-based analyses conducted on the typical design frames. In the second part of the paper, the performance of the case study frames has been re-evaluated in the light of displacement-based principles. A recently proposed method for displacement-based seismic assessment of existing RC frame structures has been implemented for this purpose, from which it has been concluded that the displacement-based approach predicts very similar overall displacement demands for such frames. These results, whilst limited to the consideration of a small number of seismic frame structures and a single, typical strong earthquake ground motion, nevertheless give confidence that the displacement-based approach can rapidly and easily facilitate a seismic assessment of an existing RC structure, without the necessity to undertake detailed inelastic dynamic analyses.