Nonlinear response modeling of low-rise structural walls

A finite element modeling approach was validated and improved in this study, for simulating the behavior of reinforced concrete structural walls with aspect ratios of 1.0 or less, whose behavior is governed by shear deformations as well as interaction between shear and flexural responses. To validate the model, a total of fifteen squat structural walls were calibrated and analyzed using Matlab. Mechanisms of shear aggregate interlock in concrete and dowel action on the reinforcing bars were explicitly incorporated in the model formulation, and cyclic degradation parameters associated with these mechanisms were implemented in the model for better representation of the in-plane hysteretic lateral load behavior of squat structural walls. The effect of strain penetration within the wall foundation was considered in the model predictions, in order to capture the initial stiffness of the walls and their lateral load capacity in early drift levels more accurately. Refined constitutive models were used in the model formulation to represent the hysteretic stress-strain behavior of reinforcing steel and concrete, as well as behavioral characteristics including compression softening, hysteretic biaxial damage, and tension stiffening effects. Features of the experimental conditions imposed on the test specimens, such as loading under double-curvature or single-curvature, axial loading on a specimen, or presence of a weakened plane joint in the wall, were represented in the model calibration and analysis conditions. Analytical predictions of the lateral load vs. displacement responses obtained using the finite element model were compared with the experimental measurements. Comparisons revealed that the model reasonably predicts the overall lateral load vs. displacement behavior, as well as important response attributes such as the initial stiffness, lateral load capacity, cyclic strength and stiffness degradation, and pinching characteristics of the walls investigated. While it is still subject to further refinement, the analytical model in its current improved form is shown to be a feasible candidate for simulating the hysteretic lateral load behavior of low-rise structural walls.