Abstract:
It is well established that unreinforced masonry (URM) buildings develop damage-forming
collapse mechanisms during high-intensity earthquakes. After the 2010/2011 Canterbury
earthquakes, an international team of researchers documented the observed earthquake
damage and formed a dataset from where 318 URM buildings were analysed in this thesis,
contributing to an ongoing effort to compile an inventory of collapse mechanisms observed
in the different URM building typologies of New Zealand. This inventory was then
compared against a vast dataset of collapse mechanisms documented worldwide.
The main objective of this research is to investigate the use of the Discrete Element Method
(DEM) of analysis in the prediction of URM dynamic behaviour subjected to earthquakes
and the development of collapse mechanisms, sampling from the inventory. The DEM can
realistically simulate phenomena that involve large movements between elements, making
it ideal for simulating the collapse of URM buildings. Consequently, extensive research
applying DEM to solve URM problems has recently been published. One of the most
critical parameters to define in DEM rocking simulations is the damping approach that
generally authors overlook or assign without thorough consideration, probably due to a lack
of literature available on the topic.
Consistent guidelines related to the assignment of damping factors was developed and
validated for rocking façades and parapets as part of this thesis. Pulse-like accelerations,
generally associated with near-fault earthquakes, were found to cause collapse of parapets
and façades at substantially lower accelerations when compared to earthquakes with
oscillations that were evenly distributed in time. Pulse-like accelerations were also used to
investigate the progression of the collapse mechanism development in two-way spanning
URM walls using the DEM, from the initial formation of the mechanism up to the final
collapsed state. Lastly, a blind prediction simulation was performed using the DEM of two
adjacent URM buildings seismically tested on a shake table. The overall behaviour in terms
of base shear force, building displacement, damage progression and pounding was
reasonably well captured by the DEM model.