Abstract Summary
This contribution presents the structure of a developed software for static and transient linear-elastic coupled Finite Element (FE) – Boundary Element (BE) analyses and demonstrates its application for the analysis of soil-structure interaction of portal frame bridges in two and three dimensions shown. Particular attention is given to the formulation and implementation of the elastodynamic boundary element method in two and three dimensions, with a separate discussion of its dimension-dependent properties. Major part of the Finite-Element formulation is outsourced to commercial software, with the import of FE models from ABAQUS realized in the current implementation. For the transient analyses, the system matrices of the FE and BE model are assembled using a direct coupling strategy at the interface nodes of the two subdomains. To ensure the reliability and stability of the numerical computations, special attention is paid to the subdivision of boundary elements and the implementation of a time-weighted method. This general-purpose computer program is subsequently used to model and analyze portal frame bridges. Herein, the bridge structure is modeled by FE, while the half-space is discretized by BE, which allows an adequate description of wave propagation in the subsoil toward infinity. With this modeling strategy, the natural frequencies and geometric damping of the portal frame structure are determined, based on the free vibration response of the frame structure due to impulse loading. By parameter variation and comparison of analyses in 2D and 3D, different modeling variants for determining geometric damping are assessed and differences, as well as limitations, are shown.
