Technical
			COST - EFFECTIVE TESTING OF BRIDGES. Bridge testing has traditionally involved measuring deflections and / or strains under service loads, by installing various types of electronic instruments to key elements in a bridge. Whilst this approach is able to provide accurate information about the load response of a bridge, it usually takes a considerable amount of time and tends to be relatively expensive. For many Council's the cost of undertaking such tests may have a significant impact on the total budget of funds available to undertake bridge maintenance and only one or two bridges might be able to undergo testing in a single year. AccessUTS Bridge Diagnostics evolved out of the need to develop a cost – effective and accurate method for assessing the structural condition and predicting the load capacity of timber bridges for local government in Australia. The aim of the R&D project, which was undertaken in collaboration with IPWEA and a number of NSW Councils was to be able to test bridges, was to be able to test quickly and at a cost of about $5000 per bridge (based on 2 - 3 spans). The R&D project met these aims by developing a technology which is based on analysis of fundamental frequency of the superstructure to determine the global stiffness of a bridge deck. This assessment procedure involves the attachment of accelerometers underneath the bridge girders. The vibration response and natural frequency of the bridge superstructure is measured when a “calibrated sledgehammer” is used to hit the unloaded deck, and then again with a relatively small mass applied at mid-span. The difference in response allows the load carrying capacity of the bridge to then be calculated, using a reliability based strength model, derived from extensive testing of aged timber girders. Funding by the Roads and Traffic Authority of NSW in 2003 - 2004 has enabled a number of significant enhancements to the accessUTS bridge testing capability. These include refinements in efficiency when testing “in the field” and some significant developments in how damage can be detected in individual girders. One of these developments also permits a much clearer signal to be obtained and is particularly important for concrete bridges or timber bridges with thick concrete overlays. A general description of the assessment method is presented in the paper entitled "TESTING AND ASSESSMENT PROCEDURES TO FACILITATE THE MANAGEMENT OF TIMBER BRIDGE ASSETS", which can be downloaded here. Examples of typical reports are also available upon request: enquire@bridgediagnostics.com.au
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