Characterization and repair of historic stone masonry structures.

摘要

The 2005 National Building Code of Canada (NBCC) requires that buildings be able to resist an earthquake that can occur once every 2500 years (2% chance of exceedance in 50 years). In a project to maintain and conserve the Parliament Buildings of Canada, it was required to assess the buildings in relation to their ability to conform to the requirements of the NBCC. For older buildings like the Parliament Buildings of Canada, the code requires that such buildings be able to resist at least 60% of the forces exerted on it by the 1 in 2500 years earthquake. Therefore, it was necessary to evaluate the capacity of the buildings on Parliament Hill, and the loads that could develop in the buildings in the case of an earthquake of the expected magnitude. In order to calculate the capacity of the buildings, and the forces exerted on them by an earthquake, certain properties of the walls constituting the building should be identified like the elastic modulus and the shear modulus. This thesis focuses on determining these properties for walls representative of the West Block of the Parliament Buildings, the building currently undergoing maintenance.;The West Block is constructed from unreinforced stone masonry walls. The walls are multi wythe with an outer face of sandstone, and an inner of limestone, surrounding a rubble core of dressed stones and mortar. Eight wall specimens representative of the walls of the West Block were built with materials similar to those used in the building. The walls were 2.75 m high, 2 m wide and 0.54 m thick. Five potential strengthening techniques were applied in the walls, all being through-the-wall anchorage systems. The walls were tested in different conditions to obtain the properties sought, as well as any other information about the properties of the walls and their behaviour. The walls were tested under eccentric and concentric axial compression, shear, flexure, free vibration, slow and high frequency racking, at which push/pull lateral loading cycles were applied on the walls, and out-of-plane shake tests, where the walls were subjected to scaled earthquake signals on a shake table. The results obtained from the axial, shear and flexure tests were analyzed to obtain the properties sought. The behaviour of such walls was found to be much more complicated than originally thought. Unexpectedly, the plain walls survived all of the tests with little damage, demonstrating their robustness. None of the proposed strengthening techniques were found to make a significant difference to wall behaviour. A large amount of data was obtained from the tests that are reported here. However, this thesis is focussed on analysing the "static" results for the information of interest, and assessing the proposed strengthening techniques. The dynamic data are analysed qualitatively, with the in-depth detailed analysis being left for future research.;The question was also raised as to what strengthening measures could be implemented if the walls needed such treatment, as it was expected that the unreinforced masonry walls would not be able to survive such an earthquake. Accordingly, several potential strengthening techniques were assessed during the study.