Mechanical characterisation of wall tie connection in cavity walls

The assessment of the seismic response of unreinforced masonry (URM) buildings has been a popular topic all over the world in the last decades. In recent years, induced seismicity in the north of the Netherlands increased considerably and introduced seismic risk also in this country. The built environment in the region is mainly composed by unreinforced masonry buildings, which are not designed for seismic loading and have specific characteristics such as the use of cavity walls.
An extensive large-scale testing program has been recently carried out at Delft University of Technology to characterize the behaviour at material and structural level of the terraced house typology, which is characterised by the presence of cavity walls with loadbearing walls of calcium silicate bricks and veneer walls of perforated clay bricks. Experimental tests showed that the wall ties are able to connect the two leaves for small loads, but they may fail for higher accelerations and increase the probability of out-of-plane collapse of the wall. In this framework, the paper reports the outcomes of an extensive testing campaign on the connections between the two leaves of cavity walls under large imposed displacements, aiming at providing a complete characterization of the behaviour of the connections in terms of resistance, envelope curve and dissipated energy. The specimens were composed by the typical wall ties employed in Dutch terraced houses, embedded either in calcium silicate brick masonry or in perforated clay brick masonry. Different loading conditions (axial and shear, monotonic and cyclic loading) and different confining compressive loads on the couplets were considered.