How to Stop the Rot? Continuous Monitoring of Short Span Timber Beam Bridges

This paper presents the results of an investigation of a prototype system for determining the daily structural performance of timber beam bridges. Local Government authorities in New South Wales are reported to be responsible for 2500 timber bridges. The lack of appropriate resources thwarts satisfactory maintenance, thus the need to identify a low cost method of continuously measuring the health of individual spans. Measurement of bridge girder deflection has been variously reported as an effective indicator of performance. Many existing measurement techniques apply to bridge measurement, but few can be applied to short span timber bridges with appropriate accuracy or suitable mounting method. One technique, adapted to gather typical data has been applied to a sample bridge. Data, representative of the normal traffic flow over the sample structure, were used to develop a method of identifying structural health. The data comprised deflection measurements for a typical 24-hour period with daily reports interpreted for their temporal behaviour pattern. This monitoring technique will lead to the identification of component lifetime in the presence of degradation and enable the replacement of components prior to wear out. It will also allow for more precision in setting particular load limits for bridges while enabling a more effective prioritisation of remedial work.