Influence analysis of damping on constant-ductility seismic resistance spectra for seismic design of structures

In the displacement-based design,the constantductility seismic resistance spectra are very useful for the preliminary design of new structures where the global displacement ductility capacity is known,which can provide the required inelastic lateral strength of new structures from the required elastic lateral strength.The influences of period of vibration,level of ductility ratio,damping,etc.on constant-ductility seismic resistance spectra are investigated in this paper.And the special emphasis is given to influence analysis of damping on the inelastic spectra.A statistical study is performed of inelastic response computed for different damping ratio SDOF systems with different levels of lateral yielding strength required to maintain the given displacement ductility ratio when subjected to a large number earthquake accelerations.It is concluded that the damping′s effects on constant-ductility seismic resistance spectra are rather complex.It depends on not only site conditions but also the level of ductility ratio and the natural period of structures as well. Finally,results from non-linear regression analysis are presented that provide a simplified expression to be used to approximated quantify the damping influence.Numerical analysis shows the simplified expressions are adequate for the seismic design of structures.