A report on the performance of unreinforced masonry buildings in February’s Christchurch earthquake has recommended measures to reduce falling hazards, unify national policy and increase seismic research.
The report recommended that all unreinforced masonry buildings should be improved to reduce the risk of falling hazards, that the country should have a single national policy for maintaining and strengthening these buildings, and that field testing should take place on some buildings in the Christchurch Central Business District (CBD) to improve seismic knowledge.
The report was prepared for the Canterbury Earthquakes Royal Commission in Christchurch.
Some 40 people died in the 22 February 2011 earthquake due to the failure of unreinforced masonry buildings in and near the Christchurch CBD.
The report’s main recommendations are:
- All unreinforced masonry buildings should be improved so that the public is protected from all falling hazards such as chimneys, parapets, gable end walls and out-of-plane wall failures. These parts of unreinforced masonry buildings should be improved to the full design strength required for new buildings in New Zealand.
- There should be a single, national policy for unreinforced masonry building maintenance and seismic strengthening rather than multiple regional policies.
- A cost effective strategy is needed to direct the limited resources available to tackle the problem of upgrading all of New Zealand’s approximately 3,867 unreinforced masonry buildings to a minimum of 67% of the new building standards requirements.
- Field testing of a limited number of existing unreinforced masonry buildings in the Christchurch CBD or nearby (that have been listed for demolition) would improve the current understanding of the seismic capacity of these buildings as well as offer an opportunity to develop and validate more cost-effective seismic strengthening/retrofit technologies. Such testing would focus on global structural performance characteristics and how loads are transmitted through buildings, and would be undertaken using such techniques as snap back testing to generate lateral loads and deformations that simulate earthquake effects.