New opensees models for simulating nonlinear flexural and coupled shear-flexural behavior of RC walls and columns

This paper describes new model elements and material constitutive relationships implemented by the authors into the widely-used open-source computational platform OpenSees (Open System for Earthquake Engineering Simulation), aimed to enhance current nonlinear analysis and response assessment capabilities for reinforced concrete (RC) walls and columns. Classes added to the existing OpenSees library include: (1) the Multiple-Vertical-Line-Element-Model (MVLEM) element with uncoupled axial/flexural and shear responses, (2) the Shear-Flexure-Interaction-Multiple-Vertical-Line-Element-Model (SFI-MVLEM) element with coupled axial/flexural and shear responses, (3) the Fixed-Strut-Angle-Model (FSAM), which is a two-dimensional constitutive model for RC panel elements, (4) an improved uniaxial constitutive model for concrete, and (5) an improved uniaxial constitutive model for reinforcing steel. Representative validation studies are also presented, where the analytical model predictions are compared with results of quasi-static lateral load tests on selected RC column and wall specimens. Response comparisons reveal that the implemented models capture, with reasonable accuracy, the experimentally-observed behavior of the test specimens investigated. Based on the comparisons presented, model capabilities are assessed and potential model improvements are identified.