Seismic modification factors for box girder bridges using a proposed pushover technique incorporating torsional vibration modes

This paper presents the results of numerical investigations on seismic modification factors (R) for algerian box girder bridges (BGBs) with both equal and unequal pier heights, using a proposed pushover technique that incorporates torsional vibration modes. In the first part, the BGB referenced in a project by the Algerian Highway National Agency is selected to evaluate the components of the R-factor in the transverse direction. Conventional pushover analysis (CPA), employing the elastic first mode, uniform, and upper-bound lateral load patterns, as well as the proposed pushover technique, is conducted. The results of CPA and the proposed pushover technique for the reference BGB are examined in terms of R-factor components, including overstrength (Ω) and global ductility (R-µ), and are compared with those obtained using the incremental dynamic analysis (IDA) technique. The findings indicate strong agreement between the proposed pushover technique and the IDA technique.