Rocking response assessment of in-plane laterally-loaded masonry walls with openings

Finite element (FE) simulations of lateral loading tests on a full-scale masonry wall with an opening were processed to investigate the observed rocking response before and after strengthening. The lateral drift of the piers and spandrel panel was decomposed in a part associated with both bending and shear deformations and another part associated with rocking rotations of end sections. FE analysis results show that: (1) the ratio between rocking rotations of the spandrel panel and those of the piers can be predicted through a simple geometrical relationship; (2) overturning moment can induce significant axial force variations in piers, changing their lateral behaviour. A sensitivity analysis demonstrated that rocking response was not significantly affected by variations in fracture energies of masonry units and mortar, opposed to the case of individual solid masonry walls. Finally, a simplified analysis of individual piers and macro-element matrix analysis of the as-built sub-assemblage was performed. Several options in terms of pier effective heights, spandrel effective length, size/stiffness of spandrel–pier overlapping zones, and reduction of elastic properties have been tested against experimental and numerical results. It is shown that: (1) lateral drifts in uncracked elastic conditions can be predicted via equivalent frame models with rigid end offsets and different effective heights of piers, depending on their location and performance level considered; (2) reduction factors of elastic properties lower than those allowed by some national and international codes may be required to capture large rocking-induced lateral drifts.