Simplified frame models to simulate the in-plane load–displacement response of multi-story, perforated, partially grouted masonry walls

Abstract

Equivalent frame models can be considered a relatively simple alternative in modeling masonry shear walls. Therefore, this study employed linear and non-linear frame models to simulate the in-plane load–displacement response of multi-story, perforated, partially grouted masonry walls. Different configurations of linear frame models were assessed for replicating the initial lateral stiffness of the walls: additional involvement of seismic performance factors (SPFs) and ultimate top drift limits enabled assessment of prediction of an idealized load–displacement response. Also, a new non-linear frame model approach was further evaluated to simulate the actual load–displacement response of the walls. Results indicated that including rigid offsets on the horizontal and vertical elements of the portal frame model resulted in a lateral stiffness and internal loads closest to that of experimental walls. It was possible to reproduce the idealized lateral response of the walls using the initial lateral stiffness of the linear models associated with adequate SPFs and ultimate top drifts. The idealized curves better matched the actual response when the lateral stiffness of the linear models was closer to that of the reference walls. An imposed ultimate drift higher than the actual amplified the estimation of the lateral load capacity and vice-versa, using all the approaches assessed. Values of 0.4% and 0.2% for the ultimate top drifts proved to be reasonable options for the cases in which the walls were submitted to a pre-compression of 0.04 fm′ and 0.2 fm′, respectively. Furthermore, the proposed non-linear braced frame model could predict the envelope curves of the experimental walls up to the peak load but did not present the expected strength degradation in the post-peak stage. Model BF could represent the distribution of loads between the elements only in the linear phase. It is necessary to make further adjustments to this model to account for the interaction between axial load and moment in the strength capacity of the flexural plastic hinges without compromising numerical convergence.