Serviceability design for masonry structures subjected to foundation movements

In Australia and other regions of the world, unreinforced masonry is extensively used in the construction of domestic and commercial structures. Such structures are typically light weight and are supported on shallow, and relatively flexible, footing systems. This, together with the inherently brittle nature of unreinforced masonry, results in these structures being susceptible to damage from differential movements of the foundations. Differential foundation movements may result from various effects such as moisture movements in reactive soils, mine subsidence and differential settlement. These effects typically create angular distortions, and therefore stresses, in walls and commonly result in serviceability problems such as jamming of doors and windows and masonry cracking. Existing design measures for the serviceability limit state are largely empirical, based on the performance of structures in service. The research reported in this thesis forms part of a group research effort to develop rational design criteria for the serviceability design of masonry structures. The study has focused on the problem of masonry cracking, particularly in response to swell and shrink movements in reactive soils. The work embodied in this thesis represents the first attempt at probabilistic modelling of the response of masonry wall/footing systems to reactive soil movements which is based on analytical modelling of the fundamental system behaviour. The work involved: - The development of a deterministic soil/structure interaction model for the simulation of the structural response, including wall cracking, of lightweight masonry structures to reactive soil movements. This numerical model was specifically designed for use in the probabilistic modelling of soil/structure interaction behaviour. - The above model was used to develop a probabilistic model for wall cracking. The probabilistic model allows for variability in the external effects (influencing reactive soil movements) and the structural response to the movements. The model considers not only the probability of masonry cracks developing, but also the probability of subsequent crack widths exceeding acceptable limits. The probabilistic model, combined with acceptable limits for cracking, can be used as a basis for the development of rational criteria for serviceability design.