Seismic Design of Steel Structures Based on Ductility

In this paper a simple tool for seismic design of steel structures for a selected ductility level is presented. For this purpose, a consistent set of earthquakes is selected and sorted based on the maximum acceleration of ground surface. The selected records are applied as the base motion to a single-degree-of-freedom system with strain hardening and the maximum response acceleration is determined for three levels of ductility. The response results of the nonlinear dynamic analysis are presented in the shape of the maximum acceleration of the system versus the peak ground acceleration for a certain ductility demand. Using these graphs, the maximum acceleration and base shear of the system are calculated by accounting for its nonlinear behavior, hence eliminating the need for the response modification factor. This is the main advantage of the presented diagrams for nonlinear seismic design of steel moment frames.