Determination of Equivalent Damping Relationships for Direct Displacement-Based Seismic Design Method

Abstract

The relationships between equivalent damping and ductility for the direct displacement-based seismic design (DBSD) method are proposed in the paper. First the concept of the DBSD is addressed to highlight the importance of the proper determination of equivalent damping. In the DBSD, the equivalent stiffness is taken as the secant stiffness at maximum deformation, so the appropriate equivalent damping should be determined based on such a prescription. Then various equivalent damping relationships proposed by different methods are outlined and the appropriate equivalent damping relationships for the DBSD are proposed with the aid of extensive dynamic time-history analyses of single-degree-of-freedom (SDOF) systems with different moderate hardening behavior. The influence of the hardening behavior on the equivalent damping would be reflected in the proposed relationships. Finally twenty-one SDOF systems are designed according to the DBSD procedure and analyzed to indicate that the proposed equivalent damping relationships are suitable for the DBSD.