Inelastic seismic demand spectrum with Ay-Dy format based on soil conditions classifications and characteristic periods grouping

The nonlinear response spectrum is one of the fundamental subjects to be solved in performance-based seismic design. The inelastic seismic demand spectrum with the yield spectral acceleration-yield displacements format has the advantage that structural periods corresponding to intersection between radial lines and demand spectrum curves with different yield strength factors are all the same and this provides convenience to realize multiple-level anti-seismic objectives in displacement-based seismic design. In this paper, 434 earthquake ground motion records on I~IV soil sites are classified into 12 groups according to the soil conditions and ground motion characteristic periods grouping specified in Guide to seismic Design of Double Deck Viaduct. By a great deal of time history analysis of single degree of freedom, the seismic demand spectra with Ay-Dy format based on soil conditions classification and ground motion characteristic period grouping are produced. The influence of the level of strength of the structure, vibration periods, soil site classifications and ground motion characteristic periods grouping on the seismic demand spectrum is studied. By means of nonlinear regression analysis, the regression expression adaptive to different soil conditions, different ground motion characteristic period grouping and different strength levels is obtained, which can be applied in analytic calculation of nonlinear displacements of structures. An example is provided to explain the design process using the research results of this paper, and the correctness of the research results is verified by comparing to the outcome of the existing literature.