Full-scale Experimental Pushover Testing of an Existing URM Building

Due to the large number of existing unreinforced masonry (URM) buildings worldwide, and the significant seismic risk that this building stock represents, it is important to quantify the seismic behaviour of such buildings in order to provide assessment guidance to practicing structural engineers. Current assessment guidelines have received little benchmarking against the results of large scale lateral testing of typical URM buildings. In response, field testing was performed on a decommissioned vintage URM building to investigate the in-situ behaviour of URM piers and compare actual behaviour to that predicted by existing assessment frameworks. The tested building was a prototypical, three-storey, 1930s fired clay brick URM building located in Auckland, New Zealand. A pushover test was performed by applying a load to the roof level of the building with a 22 tonne excavator, resulting in the formation of a pier rocking mechanism consistent with the predicted modes determined using current assessment guidelines for URM piers. Finite element modelling was able to replicate the results of the experimental testing, but a reduction of the masonry elastic modulus when acting in tension was required in order to match experimental force-displacement response. The calibrated finite element model was subjected to a pushover analysis of the entire building and was used to benchmark the ability of common seismic assessment techniques and simplified macro-element models to predict failure mechanism and building capacity. It was found that macro-element models tended to under-predict the capacity of the building unless an artificial rigid diaphragm constraint was introduced, and that current assessment techniques and 2D macro-element modelling of individual facades provided a dependable lower bound on the capacity of URM frame-type buildings.