Performance of Unreinforced Masonry Buildings in Canterbury Earthquakes

This paper describes the impact of the 4th September 2010 and the 22nd February 2011 Canterbury earthquakes on masonry buildings. Christchurch and the surrounding areas have more than a thousand old buildings built of unreinforced brick and stone masonry. Several unreinforced masonry (URM) buildings were damaged (some very severely) in the September earthquake; whereas the February earthquake caused severe damage (many collapsed) to most URM buildings in Christchurch; requiring them to be demolished. As expected, retrofitted URM buildings generally performed better, but in the February earthquake several retrofitted buildings were also severely damaged. URM buildings with perimeter walls partially anchored using small and sporadic anchor bolts not extending to the full perimeter and height of the walls suffered severe damage. On the other hand, URM buildings that were systematically retrofitted to avoid the perimeter walls from detaching from each other and from the floor and roof sustained the severe shakings of the February earthquake with only minor damage.