THE INFLUENCE OF RESPONSE SPECTRAL SHAPE OF EARTHQUAKE GROUND MOTIONS ON NONLINEAR SEISMIC RESPONSES OF REINFORCED CONCRETE GIRDER BRIDGE STRUCTURES

Earthquake experience has shown that the comprehensive influence of key characteristics of earthquake ground motions, namely amplitude, frequency content, duration, on all kinds of structures accounted for their failure and destruction in an earthquake. The incremental dynamic analysis of a six span reinforced concrete continuous girder bridge using real accelerograms and spectral matched artificial accelerograms is performed for decoupling the influence between frequency content and duration or amplitude on structural seismic responses. The comparison of correlation between frequency content of earthquake ground motions, especially response spectral shapes and nonlinear seismic responses of RC girder bridge structures reveal that the spectral shape has more and more important influence on nonlinear seismic responses with the increase of ground motion intensity measures and the extent of nonlinearity of bridge structures. If there is a higher modal effect in the longitudinal or transverse direction of bridges, the interaction of the higher modal effect and spectral shape can enhance the influence of frequency content on nonlinear seismic responses of bridge structures. Furthermore, spectral shapes in various parts of response spectra have significantly different effects on nonlinearity of responses of bridge structures of different dynamic properties and key parts of response spectra of remarkable effects on nonlinear seismic responses of RC girder bridge structures are predicted.