Rotation and damage index demands for RC medium-length span bridges

The necessity of improving the assessment of the expected economic losses by the earthquake actions has motivated the evolution of several proposals, aimed at evaluating the bridge seismic demands under different seismic scenarios. The most reliable methodologies to determine the seismic demands are the non-linear time history analyses, however, the computational time required can be excessive and the applicability of the outcome is usually limited for the analyzed bridge. Several studies have proposed analytical expressions to assess engineering demand parameters (EDP’s) as function of an intensity measures (IM’s) for some seismic regions and in most of the cases for displacement or drift demands. The objective of this research is twofold: to determine relationships IM-EDP functions, for typical highway RC bridges in Mexico and to quantify the influence of joining the seismic data of two important seismic sources on the bridge EDP’s. The IM selected in this study, was the spectral acceleration for the fundamental period of the bridge and the EDP’s were the pier plastic rotations and the bridge damage indices. For this purpose, the response of a family of bridge models located in four different seismic zones was assessed. The bridges were subjected to 124 seismic records from earthquakes with origin on the two most important seismic sources in Mexico, namely: subduction fault and deeper inslab fault. Finally, empirical equations were proposed, based on the 7936 nonlinear time history analyses.