In-plane flexural behavior of hollow brick masonry walls with horizontal holes

Abstract

Recent seismic events proved that buildings built with hollow brick masonry walls performed quite poorly when subjected to horizontal actions. To provide insights, an experimental study was conducted to evaluate the flexural behavior of existing slender masonry walls built with clay hollow bricks with horizontal holes and cement-based mortar. Two full-scale specimens were designed and built to exhibit an in-plane rocking behavior when subjected to cyclic horizontal loads such as those induced by an earthquake; the pivotal aim of the experimental test is to assess the actual ductility of such a mechanism for this specific wall typology. The test results show that, unlike other masonry wall typologies exhibiting ductility in the case of in-plane flexural mechanism, this construction typology performs quite poorly under horizontal loads also in the case of rocking, with very little deformation capacity, which reduces by increasing the compressive strength of the mortar. A sudden failure was observed for quite reduced drifts in the experimental tests; failure was associated with the brittle crushing of the pier toe, in which compressive stresses were concentrated. The brittle collapse mechanism also entails the inability of the wall to further sustain the vertical loads, once the ultimate in-plane flexural capacity is reached. A numerical study was carried out; the finite element model was validated against the experimental results. The comparative assessment showed that the finite element model accurately predicts the structural behavior, lateral strength, and failure mechanism of the specimens. Parametric analyses on the validated finite element model (FEM) were carried out to further investigate the structural behavior of different wall layouts or mechanical properties. Finally, a simplified bilinear behavior-curve is proposed to model the flexural response of slender walls, which can be specifically implemented when addressing an equivalent frame approach in the seismic vulnerability assessment of existing buildings built with the analyzed construction typology.