A new layered shell model for reinforced concrete walls I: model description and dynamic response simulations

Increasingly widespread use of nonlinear response history analysis methods for performance-based design/assessment of buildings with complex reinforced concrete (RC) wall systems has underlined the need for development and implementation of more robust nonlinear modeling approaches that can simulate important (yet commonly-ignored) nonlinear response characteristics of RC walls, such as shear-flexure-torsion interaction, plane sections not remaining plane, warping, out-of-plane behavior, nonlinear shear deformations, and shear stress migration across wall cross-section. Such advanced modeling approaches for walls need to be implemented in widely-accessible computational platforms that are capable of efficiently simulating the dynamic response of entire three-dimensional structural systems incorporating walls, under multi-directional seismic excitations. Furthermore, studies available in the literature on dynamic testing of walls and wall systems, and studies on detailed validation of refined wall models against data obtained from such dynamic test campaigns, are both scarce. With these considerations in mind, a new finite element modeling approach, referred to as the Layered Fixed-Strut-Angle Finite Element (LFSAFE) model, was developed and implemented in the widely-accessible analysis platform OpenSees. In this paper, the constitutive behavior and working principles of the LFSAFE model element are summarized. As well, nonlinear dynamic response simulation capabilities of the model are evaluated, via comparison of model response simulations with shake table test results conducted on (i) a half-scale isolated U-shaped wall specimen subjected to bi-directional ground accelerations, and (ii) a full-scale ten-story wall-frame building specimen subjected to three-directional ground accelerations. The three-dimensional dynamic response simulations presented in this paper demonstrate that the LFSAFE model is efficient in replicating, with reasonable accuracy, the experimentally-measured seismic displacement, acceleration, and deformation demands developing on both the U-shaped wall specimen and the three-dimensional wall-frame building system investigated. Capabilities of the LFSAFE model are demonstrated, and its limitations are identified.