Practical examples of using qualitative assessment methods to assess the earthquake risk of historic structures in the Christchurch area

The New Zealand Society for Earthquake Engineering recommends a qualitative procedure for assessing the earthquake risk of buildings. This procedure has become a requirement by both local authorities and building owners with the results holding more weight than was perhaps originally intended. While the procedure is valid for the majority of building types, many historic buildings will fall into the lowest classification despite any qualities they may have. To remain in use the building will usually require a detailed quantitative assessment, which is often not feasible. This paper considers that as historic buildings are often non-engineered, qualitative assessments are more appropriate than quantitative assessments. Three practical examples are presented. The assessments use the principals of the NZSEE qualitative procedure and extend them to provide a comprehensive qualitative assessment. They aim to produce a more appropriate risk classification based on identifying past performance, historic and current use, structural qualities of weaknesses, damage causes, probable collapse mechanisms and highest risk elements. The assessments also enable the identification of a pragmatic approach for improving the building’s performance. The buildings assessed are all managed by the Department of Conservation and include: Fort Jervois on Ripapa Island (1880), The Sign of the Packhorse Hut (1916) and Godley Head Battery (1940s).