Evaluation of timber bridges using stress wave technology

The focus of this research was to develop stress wave NDE techniques for determination of the in-place properties and strength of timber bridge components. Current inspection procedures for timber bridges is often an art involving visual assessments of the degree of decay and mechanical damage and of the extent to which the deterioration has penetrated into hidden regions of the structure. NDE techniques utilizing stress waves has successfully been used to improve the assessment of the integrity of wood structures. The research results show improved stress wave velocity methods that more accurately quantify the residual strength of wood members and the timber bridges themselves. These improved methods have been applied to wood bridges and piles that had been targeted for replacement. Stress wave evaluations were performed on the bridges in-place, followed by destructive testing of elements of the bridges and piles after demolition to verify the NDE conclusions. While the application of the stress wave methods in this study is for softwood timber bridges, the methods are applicable to all timber bridges. The ultimate goal of the research is to develop a comprehensive handbook for bridge inspectors which provides guidelines on the use, application and interpretation of stress wave methodology for locating and defining areas of deterioration in timber bridges. This presentation discusses the theory of stress wave technology, user guidelines for equipment use, interpretive procedures, and procedural guidelines for assigning design values to in-place bridge components and for assessing in-place capacity.