Analysis of an Integral Abutment Bridge Based on Unified Boundary Condition and Grillage Model

Abstract:

Without expansion joints and bearings， integral abutment bridges can avoid the disease of expansion joints and the impact on driving. Since the superstructure and the substructure at the abutment are poured together， the force of the superstructure of integral abutment bridge is affected by the substructure and the soil， the calculation requires comprehensive consideration of the superstructure and the substructure， and the calculation method is more complex. The author proposes a new idea to realize the verification and adjustment of the superstructure under different load combinations. In this paper， a two-span integral abutment bridge is used as a supporting project， the boundary conditions are extracted under representative working conditions through a solid finite element model and applied to the grillage model of the full bridge， then we can complete the calculation and design of the integral abutment bridge， the specific process is as follows： In the solid finite element model， establish a simplified "single beam + single pile" model， and use the "m" method to determine the stiffness of the soil spring to simulate the structure-soil interaction； calculate the axial force and the linear displacement at the centroid of the beam end under the overall heating condition， and the bending moment and angular displacement at the beam end under mid-span loading condition， then convert them into two linear springs with a certain distance， which are applied to the grillage model of the full bridge as a boundary condition. In the grillage model， the internal force and bearing capacity of the full bridge under various working conditions are obtained， then the design of the integral abutment bridge is completed. In non-rock foundations， when the structure-soil interaction is simulated by the "m" method， the feasibility of the simplification and the design method has been verified.

Key words:integral abutment bridge;“m” method;“single beam+ single pile” model;boundary condition;grillage model