A parametric study on out-of-plane instability of doubly reinforced structural walls. Part II: Experimental investigation

The effects of different parameters on the evolution of Out-Of-Plane (OOP) instability in rectangular walls were studied using a validated FEM model. Based on this parametric analysis, a test matrix was designed to experimentally investigate the progression of this mode of failure in rectangular walls. Results of the parametric study were presented within a companion paper, while the experimental observations as well as the numerical versus experimental comparisons are presented in this paper. The wall specimens were tested under in-plane cyclic loading and they exhibited different OOP responses. The development of OOP mechanisms was observed in all tested specimens, albeit with different values of maximum OOP displacement and followed by different types of instability. Progression of OOP deformation was suppressed by other failure modes in all specimens except one which failed due to large OOP displacement and global instability. In this study, the progression of OOP deformation and its relationship with the inelastic strain gradients of the longitudinal reinforcement along the length and height of the specimens are scrutinized and the numerical predictions are compared with the test measurements. The experimental findings regarding the evolution of this mode of failure and the influential parameters are in good agreement with the numerical predictions. However, the onset of OOP deformation typically had a delay in the numerical model when compared to the test results. One of the factors inducing this difference could be the effect of inherent and mostly unmeasurable eccentricities, including material, geometry as well as loading imperfections, which were not included in the model.