Characteristics of earthquake response for long-period structures and response spectrum

The characteristics of earthquake response for long-period structures,and a few shortages existing in the response spectrum of China code for seismic design of buildings are analyzed. It can be clearly found that an artificial modification to response spectrum can result in the distortion of ground motion characteristics. The revision to the longperiod segment in the response spectrum of China code can cause the change in the characteristics of ground motions, which results in an abnormal representation of power spectrum corresponding to acceleration spectrum. The analysis results show that the calculated displacements of long-period structures under earthquake action are over estimated. Minimum story seismic shear coefficient described in the specification is only related to maximal earthquake influence coefficient( αmax),but is not related to site classification,which is in conflict with the general rule that the earthquake responses of a structure at the soft-soil site are larger than those of a structure at the hard-soil site. According to the pseudo spectrum relations among acceleration spectrum,pseudo-velocity spectrum and displacement spectrum,a response spectrum pattern with longer-period segment( T is approximately extended to 10 s) is proposed,which can provide a reference to specification revision. Engineering cases show that calculating the displacement of structure according to the proposed response spectrum is feasible.