Experimental Investigation of Unreinforced Masonry Veneer Wall System Under Out-of-plane Loading

Unreinforced masonry veneer walls are susceptible to extreme damage and possible collapse under wind and earthquake loading. The behaviour is complex due to the interaction of the masonry veneer, the timber support frame and the wall ties which connect them. The behaviour is further complicated due to spatial variability in the properties of constituent materials. In this paper, the outcome of full-scale testing of masonry veneer systems under out-of-plane loading, which includes multiple repeat specimens, is reported. These masonry veneer wall systems represent contemporary construction practices in Australia according to AS 3700. A total of ten masonry veneer assemblies, dimensions of 2398 mm (height) × 2390 mm (length) × 110 mm (thickness), supported via wall ties to a four-stud timber frame, and theoretically identical properties, were tested to predict the stochastic (probabilistic) strength of veneer walls. Out-of-plane loading (airbag pressure) was applied on the wall’s external surface, which induced compression in the wall ties. The flexural bond strength of the brick-mortar joints was estimated by the bond-wrench test, conducted in parallel with wall testing throughout the experimental program. The typical trend of the pressure-displacement behaviour was, veneer cracking at a mean load of 1.84 kPa followed by a slight decrease in pressure. Then, the pressure climbed until it reached the veneer system peak load where randomly different rows of the wall ties were buckled or nail pulled out from the timber studs. The test was continued beyond the peak load to observe the veneer system behaviour. The coefficient of variation of peak load was found to be 11%. The nature of the veneer cracking and tie failures are reported and discussed at the end of this paper.