On effective finite element modeling for investigating elasto-plastic deformation of piping systems under internal pressure and seismic loading

To consider plastic deformations of materials in strong seismic loading, such as beyond design basis earthquakes, strain-based seismic assessments are carried out through elasto-plastic finite element analyses. However, due to the large nonlinearity and uncertainties of the model, analysis results are affected by modeling variables. Moreover, the equivalent plastic strain which is the major parameter in the assessment, tends to be sensitive to the types of finite element and the resolution of the mesh in the model. Accordingly, a modeling guideline for a reliable and efficient strain-based seismic assessment of piping systems under seismic loading is needed. In this paper, to propose such guidelines for the 3-dimensional piping systems in the elasto-plastic finite element analysis, the influences of solid element types and mesh resolution on the acceleration, strain, equivalent plastic strain results were investigated. The seismic test of the piping system under internal pressure performed by the BARC was selected for the target of analysis. To consider the cyclic hardening of materials, the Chaboche kinematic model was applied. The applicability of the existing JSME code case guideline for piping systems was validated, and the mesh resolution of quadratic solid elements that could obtain converged results was investigated. In addition, a guideline for the mesh resolution of linear solid elements that can reduce computational time by up to 4.3 times while obtaining results that converge adequately to the results of quadratic elements was proposed.