Effect of Temperature on the Modal Variability in Short-Span Concrete Bridges

The dynamic characteristics of bridges are known to be affected by damages as well as by environmental factors such as temperature. Therefore, the changes in the dynamic characteristics caused by damages and environmental factors should be considered when evaluating the health of the structure. Accordingly, this study conducted long-term monitoring and modal identification of short-span concrete bridges, i.e., a RC (reinforced concrete) slab bridge a RC rahmen (rigid-frame) bridge. The investigation revealed that temperature is the factor having the greatest influence on the variability of the dynamic characteristics as the natural frequencies of the bridge decrease with higher temperatures. Model updating verified that such modal change resulted from the temperature dependency of the elastic modulus of concrete. The RC slab bridge showed higher temperature dependency than the RC rahmen bridge owing to the presence of elastomeric bearings. Apart from the effect of temperature, non-negligible modal changes caused by other environmental factors were also identified. The results of this study are expected to provide valuable data for the health evaluation of bridges.