Energy-based seismic design of structures using yield mechanism and target drift

The use of energy as means to derive seismic design forces is discussed in this paper. The energy balance concept used in deriving seismic design forces for single-degree-of-freedom systems is extended and used to derive the design forces for multistory moment frames. The ultimate design forces are derived from input energy for a selected design pseudovelocity spectrum, a selected plastic yield mechanism, and a selected target deformation level. The characteristics of the structure, especially the ductility and the plastic yield mechanism, are explicitly used in calculating the design forces. A practical design procedure that can be used to ensure the formation of the selected yield mechanism is then briefly presented. The design procedure is based on conventional plastic design concept with some modifications. The energy concept proposed in this paper is then used to design six example steel moment frames. The results from dynamic analyses of these frames were used to evaluate the procedure. The results indicate that the procedure presented in this paper can be used as a viable alternative to current design procedures, and within the framework of performance based design philosophy.