Masonry wallettes with a soft layer bed joint: Behaviour under static-cyclic loading

• Cyclic shear tests on 16 URM walls with a soft layer bed joint are presented.
• A Mohr–Coulomb friction law with zero cohesion can predict the sliding resistance.
• The friction coefficient for rubber granulate layer is damage dependent.
• The pre-compression level influences the governing failure mode strongly.
• Considerable deformation capacity can be expected in URM walls with soft layer.

The main goal of the research project presented herein is to investigate the effect of damp proof courses and soft layer wall bearings on the seismic shear behaviour of unreinforced masonry walls subjected to cyclic actions, in particular how the lateral load resisting mechanism of the wall is influenced thereby. Unreinforced clay block masonry wallettes with soft layers of three different thicknesses (3, 5 and 10 mm), and two different materials (rubber granulate and extruded elastomer) were subjected to static-cyclic shear under varying levels of pre-compression. The soft layer was placed either in the first bed joint of the wallette or in the interface joint between the wallette and the underlying concrete slab.Soft layers were beneficial when the tested wallettes failed in sliding. Such sliding failure was observed for wallettes with rubber granulate soft layers placed in the first bed joint. This resulted in quasi-ductile behaviour of the wallettes, with a displacement and energy dissipation capacities significantly larger than those of the conventional unreinforced masonry control specimens. Furthermore, wallettes failing by sliding along the joint containing the soft-layer showed considerably less damage compared to wallettes that exhibited other failure modes at the same displacements levels. The progressive deterioration of the rubber granulate layers lead to a decreasing shear strength at larger horizontal displacements. Wallettes with extruded elastomer layers and wallettes with layers placed in the interface joint did not fail in sliding. Apart from slightly increased energy dissipation, no beneficial effect on the shear force–deformation behaviour of the wallettes could be observed in these tests.The results indicate that soft-layers with adequate material properties placed in the first bed joint have the potential to change the typical brittle shear response of unreinforced masonry walls to a more desirable quasi-ductile behaviour.