SEISMIC ANALYSIS OF LONG-SPAN CONTINUOUS RIGID FRAME BRIDGE CONSIDERING SITE NONLINEARITY, TOPOGRAPHY EFFECT AND SOIL-STRUCTURE DYNAMIC INTERACTION UNDER OBLIQUE INCIDENCE

Based on viscous-spring superposition artificial boundary and equivalent linear theory, a method for calculating the seismic response of long-span structures considering the nonlinear behavior of site, topography and soil-structure interaction effects under oblique incidence is established. Firstly, an equivalent linear method to obtain nonlinear site response under oblique SV wave incidence is introduced. Then, by using ANSYS software, a finite element model including a five-span continuous rigid frame bridge and soil profile is established. With the consideration of nonlinear soil behavior, a series of numerical simulation is performed with different topographies and site stiffness under different incident angles. The results show that the axial force increases and shear force decreases as the incidence angle goes up; the amplification of displacement response varies with different local irregular topographies. The amplification resulted from steep topography is larger than that from gentle topography. Site stiffness also has a great impact on the response of bridges and soft soils lead to much more pronounced responses than hard soils do.