Pseudo-dynamic tests on low-rise shear walls and simplified model based on the structural frequency drift

Twelve low-rise shear walls, with the same aspect ratio of 0.4 but with different structural parameters including the design frequency, reinforcement ratio and normal force, have been submitted to pseudo-dynamic (PSD) tests conducted at the ELSA laboratory of the Joint Research Centre. The focus of this testing campaign was to study the engineering margin for shear walls depending on the relative position of their structural frequency with respect to the excitation peak. After presenting the parameters of the PSD tests, three methods for identifying the structural frequency drift observed as damage occurs have been used in this paper: a numerical identification from a nonlinear pushover analysis, and two methods from experimental data, a system identification method based on an error output model and a more direct identification method based on the secant stiffness of force–displacement cycles. For each shear wall, a relationship f(X)f(X) between the structural frequency and the maximum of the top-displacement is derived from the previous methods and the consistency between the three approaches has been checked. Finally, these f(X)f(X) curves have been employed in a single degree of freedom model for predicting time–history top-displacements. The predictions turn out to be quite satisfactory, in particular when f(X)f(X) relationship is identified by the error output model.