Effective modal seismic design of two-way asymmetric-plan RC wall structures

This paper presents a new direct deformation based seismic design method called Effective Modal Design (EMD). The method is applied in this paper to multistorey two-way asymmetric-plan reinforced concrete wall structures. EMD is a generalization of the Direct Displacement Based Design method based on an inverse version (formulated herein) of the Effective Modal Superposition analysis method. The proposed EMD method should only be used when DDBD is not applicable. The accuracy and reliability of the proposed design method is verified for a wide range of asymmetric-plan reinforced concrete wall structures using nonlinear time history analysis of reasonably realistic 3D structural models. Advantages of EMD include explicit consideration of nonlinear, torsional and ‘higher mode’ effects. The method is direct without iteration and generates ‘capacity-designed’ design moments for all regions of all reinforced concrete walls in the seismic structural system. EMD only requires two response spectrum type analyses. It does not require time history analysis or pushover analysis. It is therefore relatively practical, and is intended for use in structural design offices for routine seismic design of multistorey asymmetric-plan RC wall buildings.