Application of Endurance Time Method in Optimum Seismic Design of Steel Frames Using Uniform Deformations Theory

In recent years, many research works have been accomplished to reduce the amount of losses induced by seismic hazards. In this regard, performance-based design approaches are recognized as promising tools. These approaches consist three steps: determination of performance objective, initial design and revising the design until achieving the final design. Optimization algorithm is used to automate the revising procedure (Gallagher and Zienkiowicz, 1973; Estekanchi and Basim, 2011). In linear static approaches of seismic design loading, structures with more stiffness and lateral strength are preferred, but investigations show that some cases exist that structures with lower stiffness show better behavior under seismic loadings. Therefore, it is required to use more precise modeling and analysis techniques and consider performance of the structure is multiple hazard levels in optimum design process. On the other hand, one of the most important obstacles in optimum design procedure is accurate response estimation with an acceptable computational effort. In this study, the Endurance Time (ET) method is used to estimate the response of the structure at various hazard intensity levels (Estekanchi et al. 2004). Uniform deformations theory introduce by Gong et al. (2003) is used here to acquire the optimum sections of a prototype steel frame with the least structural weight satisfying performance objectives in multiple hazard levels. Efficiency of the method and performance of the prototype structure before and after optimization is investigated and discussed. ASCE41-06 (2007) is used to define performance objectives.