Seismic Demands for SDOF and MDOF Systems

摘要

Earthquake resistant design has the objective of providing structural capacitiesthat exceed the demands imposed by severe earthquakes with a sufficient margin of safety. It is anticipated that future seismic codes will incorporate capacity/demand concepts explicitly in order to make the design process transparent and permit designs with a well defined and consistent level of protection. The research is concerned with the assessment of seismic demand parameters that are needed to implement a capacity/demand based seismic design approach. The objectives of the study are: (1) to assess the importance of different demand parameters, (2) to evaluate patterns in demand parameters that will improve one's understanding of the physical phenomena involved in seismic response of structures, and (3) to provide statistical information on demand parameters that can be utilized to assess the performance of structures designed according to existing codes and implement the proposed capacity/demand design approach. A comprehensive evaluation of demand parameters is performed for bilinear and stiffness degrading single degree of freedom (SDOF) systems. A less comprehensive but much more elaborate study is also performed on three types of multi-degree of freedom (MDOF) structures. The purpose of the aspect of the study is to evaluate the modification that must be applied to demand parameters derived from simplified SDOF models in order to account for multi-mode effects in real structures.