Observations of the performance of earth buildings following the February 2011 Christchurch earthquake

Abstract

A reconnaissance survey of earth walled buildings in the Christchurch area was carried out following the February 2011 Christchurch Earthquake. Twenty six earth buildings were inspected during the survey including historic earth buildings and recent reinforced earth buildings. Some of these buildings had previously been inspected following the September 2010 Darfield Earthquake.

The February 2011 Earthquake caused comparable patterns of damage to earth buildings as the September 2010 Darfield earthquake except for unreinforced pressed brick buildings which performed particularly badly. Reinforced earth buildings constructed since the 1990’s performed well during the February 2011 earthquake provided the overall wall bracing was adequate and detailing of the reinforcement and connections were generally in accordance with the NZ Earth Building Standards. Some older unreinforced rammed earth buildings constructed between 1950 and 1980, all of which had reinforced concrete foundations and bond beams, performed relatively well with only minor cracking. Unreinforced cob and adobe buildings in the area of strong shaking suffered significant damage and will require reconstruction or repair of the walls and strengthening of the upper floor or ceiling diaphragms. The performance of six houses are discussed as case studies that cover the range of buildings observed.