Parametric analysis on seismic behavior of integral abutment steel bridge considering SSI

A 3D finite element model of integral abutment steel bridge was established by the SAP2000 software, the nonlinear spring elements and damping elements were used to simulate the soil reactions behind the abutment and around the piles under the earthquake action, and the mode, nonlinear time history and relevant parameters of the bridge were analyzed, In addition, the dynamic and seismic behaviors of integral abutment steel bridge considering the nonlinear soilstructure interaction, as well as the influence of the main design parameters of integrated abutment system on the behaviors were studied.Research result indicates that compacting the abutment backfill, increasing the abutment height-to-thickness ratio, and increasing the foundation stiffness will increase the dominant longitudinal frequency of the bridge structure byabout 6.5%-16.0%, while H pile orientation has a minimal influence of about 1.6%.The structural seismic response significantly reduces as the abutment height-thickness ratio increases.When the abutment height-to-thickness ratio is 1.44, the top of the pile enters the plastic stage.When the height-to-thickness ratio increases to 3.15 and 3.85, the pile remains elastic.When the compactness of the abutment backfill decreases, the seismic response of the structure increases significantly, and the increment is mostly above 40%.When the orientation of the pile is adjusted from bending about the strong axis to bending about the weak axis, the maximum bending moment of the pile decreases, but the bending stress increases, and the material enters the plastic stage from the elastic stage.As the soil stiffness around the pile increases, the displacement response of the bridge decreases significantly.The maximum displacements at the top of the pile and abutment, as well as the bending moment at the pier bottom decrease by about 50%.However, the bending moment at the pile top increases by more than 40%, and the orientation of the pile has almost no effect on the displacement responses.As long as the design requirements are satisfied and in a reasonable range, the larger height-to-thickness ratio, more flexible abutment, and compacted abutment backfilling are recommended to reduce the seismic response of integral abutment bridge.When the steel H pile is used as the abutment foundation, orienting the H pile to bend about its strong axis is recommended to reduce the maximum bending stresses and displacements of the pile, abutment and pier.