Bridge health monitoring is a method of evaluating the ability of a bridge to perform its required task (also called fitness for purpose) by monitoring the response of the bridge to the traffic loads it has to withstand.
This research project, carried out in 1998–1999, is part of stage 2 of the short-term health monitoring and 'fitness for purpose' of 10 bridges on New Zealand highways, in order to develop and evaluate the methodology. The Rakaia Bridge, on State Highway 1S, crosses the Rakaia River about 50 km south of Christchurch, Canterbury region, South Island. It was selected because it is an aging (built in 1939), two-lane, concrete-girder bridge with integral guardrails, and has a low strength evaluation. It is typical of a significant proportion of New Zealand’s bridge infrastructure. Also, because it is the main crossing of this wide braided river and is very long (1757 m), this particular bridge represents a major asset to New Zealand’s transport system. The fitness for purpose evaluation indicates that the bridge is safely carrying the heavy vehicle traffic currently using this route.