Development And Application Of User-defined Material Subroutine In ABAQUS Software

Tunnel-type anchorage, a kind of geotechnical engineering structure, is the main supporting system of a suspension bridge. Since it is hard to perform a full-scale model test, numerical analysis becomes an important basis and also one of the most difficult and pivotal problems in design. Due to the complexity of geotechnical problems, a single constitutive model can't satisfy practical requests sometimes. In this paper, a new model by combining Rankine and Mohr-Coulomb criteria is adopted, and the analysis is done at the simulating platform of ABAQUS, which is famous finite element analysis software. ABAQUS is the most capable software especially for simulating nonlinear problems. It includes many different kinds of material models and failure criteria, and provides an open interface and some user subroutines that allow users to expand the main function in the form of code. However, the constitutive model needed in this research is not provided, so it is necessary to redevelop it by user-defined material subroutine interface. Establishing a constitutive model and choosing an integral algorithmic method are the crucial matters for developing UMAT subroutine. In this paper, based on the redeveloping technique of UMAT, the model by combining Rankine and Mohr-Coulomb criteria was established, and corresponding interface program was developed. The algorithmic method for updating stress adopted the implicit Euler one, which is different from common explicit methods. The UMAT subroutine shows correctness and accuracy by element tests. Based on this model, a three-dimensional (3D) elasto-plastic analysis on the tunnel-type anchorage of Siduhe suspension bridge was performed. The results had good consistency with the one from FLAC-3D analysis provided by Yangtze River Scientific Research Institute, which shows the feasibility and validity of the interface subroutine. The UMAT subroutine developed in this paper is applicable for all yield functions in the form of f (σ) =σonly by solving "five parameters"mentioned in this paper. This work expands the application range of ABAQUS in elasto-plastic finite element analysis, and set an example for developing other functions of ABAQUS and finite element software.