On optimal proportions of structural member cross-sections to achieve best seismic performance using value based seismic design approach

摘要

The value-based seismic design framework is a new design method that efficiently balances the construction resources and the seismic consequences, through reliable evaluation of the building performance at an affordable computational cost. This paper employs the value-based design approach to optimize the cross-section proportions of the steel wide-flange members. An optimization problem is proposed within the framework of value based design. Construction cost and seismic consequences are selected as the value components. Moreover, the minimum code requirements are formulated as the design constraints. FEMA-P58 framework is exploited for the prediction of the seismic consequences including the repair cost, repair time, injury, and fatality. Endurance Time method is utilized to evaluate the structural seismic responses. A set of four steel moment frame buildings representative of lowto mid-rise frames are selected for investigation. Each building is optimally designed by four scenarios: the code-based seismic design by minimizing the initial construction cost and the value-based seismic design by maximizing the building total value, and either scenario using members with fixed and free cross-section proportions. It is observed that the members with fixed proportions are satisfactory alternatives for beams of the seismic-resisting frames; but for the columns, optimal proportions turn out to be significantly different from those of the conventional steel cross-sections.