Structural health monitoring and reliability estimation: Long span truss bridge application with environmental monitoring data

The main objective of this study is to present the reliability estimation studies for the main truss components as well as the entire structural system of a long span truss bridge which is the longest in its category in the USA. It is possible to assess the safety level of a long span bridge by using a probabilistic approach in terms of its component and system reliability indices. However, most of the older long span bridges were designed based on allowable stress design and it is not possible to quantify their reliability. The reliability analysis in this study is based on the distributions estimated for dead, live and wind loads. The bridge was also subjected to long term structural health monitoring where large amount of input and response data have been collected. Analysis of the long term monitoring data revealed distinct structural behavior in terms of patterns and magnitudes under various external loading effects. As an example, it is shown that the structural responses due to temperature are not very easy to conceptualize and subsequently model using conventional analysis methods. In order to explore the effects of temperature on the structure and to include the long term monitoring data in reliability estimation, temperature-induced responses are also incorporated in the analysis. It is seen that the responses due to temperature have a significant effect on the overall system reliability.