Nonlinear Winkler-based Frame Element with Inclusion of Shear-Flexure Interaction Effect for Analysis of Non-Ductile RC Members on Foundation

Non-ductile reinforced concrete (RC) members are common in the existing RC frame buildings with the old seismic code (lightly and inadequately detailed transverse reinforcement) and may suffer shear failure or flexureshear failure. To investigate the failure behaviors of those RC structures, performancebased numerical models are needed. Thus, a new fiber frame element on Winklerbased foundation including the interaction effects between shear and flexure was developed to analyze nonductile RC frames resting on foundation, in this study. The proposed element is formulated for implementation in displacementbased finite element formulation under the kinematic assumptions of Timoshenko beam theory. As a result, axial and flexural mechanisms are automatically coupled through the fibersection model, while shear and flexural actions interact via the UCSD shearstrength model within the framework of modified MergosKappos interaction procedure to evaluate sectional shear force and shear stiffness within the shear constitutive law. Therefore, the presented model is simple, but able to capture several salient behaviors of nonductile RC frames resting on foundation, including interaction between shear and flexure, soilstructure interaction, degradation of shear strength due to inelastic flexural deformation, and shear failure. Those features and efficiency of the proposed model are demonstrated by two numerical simulations in this work.