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Earthquakes and Structures
  Volume 20, Number 4, April 2021, pages 389-403

Response modification factor and seismic fragility assessment of skewed multi-span continuous concrete girder bridges
Amir Khorraminejad, Parshan Sedaghati and Greg Foliente

    Skewed bridges, being irregular structures with complicated dynamic behavior, are more susceptible to earthquake damage. Reliable seismic-resistant design of skewed bridges can be achieved by accurate determination of nonlinear seismic demands. However, the effect of geometric characteristics on the response modification factor (R-factor) is not accounted for in bridge design practices. This study attempts to investigate the effects of changes in the number of spans, skew angle and bearing stiffness on R-factor values and to assess the seismic fragility of skewed bridges. Results indicated that changes in the skew angle had no significant effect on R-factor values which were in consonance with code-prescribed R values. Also, unlike the increase in the number of spans that resulted in a decrease in the R-factor, the increase in bearing stiffness led to higher R-factor values. Findings of the fragility analysis implied that although the increase in the number of spans, as well as the increase in the skew angle, led to a higher failure probability, greater values of bearing stiffness reduced the collapse probability. For practicing design engineers, it is recommended that maximum demands on substructure elements to be calculated when the excitation angle is applied along the principal axes of skewed bridges.
Key Words
    Skewed Bridge; Response Modification Factor (R-factor); fragility assessment; Elastomeric Rubber Bearing (ERB); Incremental Dynamic Analysis (IDA); seismic excitation angle
Amir Khorraminejad:Department of Civil Engineering, Shahid Beheshti University, Tehran, Iran/Department of Infrastructure Engineering, University of Melbourne, VIC, Australia

Parshan Sedaghati:Department of Civil Engineering, Semnan University, Semnan, Iran/ Department of Infrastructure Engineering, University of Melbourne, VIC, Australia

Greg Foliente: Department of Infrastructure Engineering, University of Melbourne, VIC, Australia

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