DYNAMIC BEHAVIOUR OF REINFORCED CONCRETE FRAMES DESIGNED WITH DIRECT DISPLACEMENT-BASED DESIGN

The Direct Displacement-based Design methodology is applied to six reinforced concrete tube-frame structures and tested using inelastic time-history analyses. Using the established design method inter-storey drifts are found to exceed assumed drift limits, and a series of changes to the design displacement profiles and lateral force distribution are proposed to improve agreement. These changes are then applied to the six frames and further time-history analyses carried out at different earthquake intensities. The inter-storey drift behaviour is found to be significantly improved, with code-based drift limits consistently satisfied. Finally a revised form of the Modified Modal Superposition is proposed to account for higher-mode amplification of column shear forces, while a simple intensity-dependent scaling factor to be applied in the capacity design process is developed for column bending moments. The suggested equations are applied to the frame designs, and found to be in acceptable agreement with time history results at a range of earthquake intensities.