Retrofitting House Foundations to Resist Earthquakes; Justification, Benefits and Costs

Abstract eng:
Most houses in New Zealand are constructed of light timber framing, with good earthquake resistance. Damage during past earthquakes was due to a lack of foundation bracing and inadequate connections within and to the foundations. This study showed that 39%, of a sample of houses in Wellington had inadequate sub-floor bracing, and 76% had some form of fixing deficiency, ranging from minor degradation to incorrect or non-existent fixings. The cost of remedies to upgrade foundation bracing, including labour, ranged between about NZ$15 per m² and NZ$50 per m² of dwelling floor area (US$10-40/m2). The total cost to upgrade all house foundations in Wellington City is over NZ$290 million (US$175 million). The estimated cost of damage to residential dwellings was calculated for a maximum credible earthquake. Damage without foundation retrofitting was estimated at NZ$3.8 billion and $1.8 billion after retrofitting (US$2.8 and $1.3 billion respectively). The overall benefit: cost ratio for retro-fitting foundation is therefore about 4. Apart from reducing the direct cost of repair and replacement following an earthquake, limiting damage will reduce casualties, reduce the demand for emergency accommodation and other services and hasten disaster recovery. When including the costs of casualties, emergency accommodation and other indirect costs, the benefit: cost ratio increased to about 13.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket