Damage to unreinforced masonry structures by seismic activity

Abstract

The extent of the damage caused to unreinforced masonry (URM) buildings during the 4 September, 2010 Darfield, NZ earthquake was recorded. General features of the 595 assessed URM buildings indicated that the majority were either one- or two-storey. The general observation from the debris of collapsed URM walls was that the kiln fired clay bricks were generally of sound condition, but that the mortar was in poor condition. In most cases the fallen debris had collapsed into individual bricks, rather than as larger chunks of masonry debris. Numerous parapet failures were observed along both the building frontage and along their side walls, and for several URM buildings located on the corners of intersections, the parapets collapsed on both perpendicular walls. Where walls exhibited some damage to in-plane deformation the cracks were mostly seen to pass vertically through the lintels over door or window openings. Perhaps the most striking aspect of this earthquake overall was the extensive amount of liquefaction and ground deformation that occurred.