Strength and Long-term Behaviour of Masonry Structures

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Masonry is widely used in structures because of its aesthetic appeal and durability. Many of Canada's heritage structures are constructed of masonry and there is a need to conserve these. The National Building Code requires that these structures be assessed and brought up to modern standards, but assessment and rehabilitaton of these structures is not easy. The first part of the proposal therefore has two themes. The first is aimed at understanding the current state of a structure, typically after the long-term effects of creep (the slow increase in deformation with time under load) and degradation due to weathering: the combined effects of these factors can cause internal cracking, which in turn leads to distress of the structure. If the causes are understood, suitable remedies can be designed. The second theme deals with the use of cross-wall anchors to strengthen a wall, with the aim being to develop a way of predicting the best orientation of such an anchor to resist the loads expected in an earthquake, and thereby help the structure survive that event. The second part of the proposal deals with the in-plane shear resistance of masonry. We do not have a good understanding of how masonry resists this type of load, so there is wide divergence in estimates of shear strength when one reviews codes around the world. Nevertheless, many buildings employ masonry shear walls to resist such loads (generated by wind for example). Work supported by the previous grant showed that the primary strength of reinforced masonry is dominated by the strength of the masonry, and that the reinforcement has significant effect only after the masonry has cracked. Thus I am proposing that the strength of a shear wall will arise from the strength of the masonry and the strength of the connection between the wall and other components of the building. I aim to develop a methodology to predict shear wall strength based on this view, and to compare results with those from my own tests and those reported in the literature. A subject of particular interest is masonry walls where the reinforcement is spaced at wide intervals, common in areas of low seismic risk, but where strength predictions are particularly poor. I will collaborate with Australian colleagues.