Performance-based Seismic Design Of Structures With Viscous Dampers Under Medium Earthquake

Performance-based seismic design was first included in code for seismic design of buildings 2010 edition. The Proposal of performance-based seismic design not only enriches the structures' performance requirements under medium earthquake, but also quantifies the design of structures. It is required to check structural members' bear capability and control structural deformation, which will ensure the realization of performance requirements under medium earthquake. But there is no uniform method of performance-based seismic design for buildings under medium earthquake in this edition, and there are some problems in the application of practical projects.The application of performance-based seismic design in structures with viscous dampers will extend the content of performance-based seismic design. By studying performance-based seismic design mentioned in the code, this dissertation proposed performance-based seismic design under medium earthquake for structures without structural control. Through comparing the seismic effects of energy dissipation structures designed by Chinese and American codes, the promotion of performance-based seismic design for energy dissipation structures under medium earthquake is possible. By studying definitions of damping reduction factors and the dynamic equation, the damping reduction factor for structures with dampers was proposed. The main research contents are as follows.(1) Performance-based seismic design under medium earthquake was introduced, which was proposed in code for seismic design of buildings 2010 edition. There are some problems in conceptual understanding and application. Some suggestions were proposed for improvement. Before performance-based seismic design, a judgment of the structure status was needed. The response spectrum method was suitable to elastic state structure, while response spectrum method based on equivalent linearization was suitable to yielding state structure.(2) American standards about seismic risk regionalization,site categories and seismic design method were introduced. Through changing the expression of load bearing capacity formula, comprehensive seismic effect index was defined to describe seismic effects. By comparing the Chinese and American comprehensive seismic effect index of structures with viscous dampers in the same return period and similar site conditions, the followings are discovered. Therefore, it is suggested that keeping-elastic state under medium earthquake, non-yielding state under medium earthquake and yielding state under medium earthquake need to be wider used in frame structures, and yielding state under medium earthquake need to be wider used in shear wall structures.(3) The difference between Chinese and American damping ratios modification factors is studied. Chinese design spectrum is modified by acceleration response spectra Ba, while American design spectrum is modified by displacement response spectra Bd. This article analyses the force situation of single-degree-of-freedom systems with different damping rations, the followings are discovered.1) Structures without structural control should use inertia force to study the design spectrum, while structure with energy dissipation devices should use restoring force.2) Structures without structural control should use acceleration response spectra Ba to modify the design spectrum, while structure with energy dissipation devices should use displacement response spectra Bd.Displacement response of single-degree-of-freedom systems was analyzed, whose effective damping ratio were 5%?10%?15%?20%?25%?30% and 40%, according to 100 seismic records. Nonlinear regression analysis was carried out to the average displacement response and functions were proposed to fitting displacement reduction factor.(4) The performance-based seismic design method for structures with viscous dampers was proposed, which used equivalent damping ratio to stimulate the inherent dissipation of energy by structure elements, post-yield hysteric behavior of the seismic force-resisting system and elements of the damping system and viscous dissipation of energy by the damping system. Nonlinear time-history analysis of examples verified the simplified method reasonable and reliable.