Effect of Temperature on Daily Modal Variability of a Steel-Concrete Composite Bridge

Abstract

Vibration-based damage detection techniques typically use changes of modal characteristics of bridges as a possible indication of damage. However, structural damages are not the only cause of these changes. This study investigates the effect of temperature variations on modal characteristics of a two span steel-concrete composite bridge in North Carolina, and addresses the extent and reason of the daily changes observed in its dynamic properties. The field testing included measuring vibration responses, deflections, and temperatures of the bridge throughout a summer day. The dynamic characteristics of the bridge, derived from measurements at different times of the day, were compared with each other. Recorded temperatures and deflections of the bridge deck were used to address the observed changes in the natural frequencies of the bridge. Results of the field testing showed that temperature variations can induce modal variability on a daily cycle. A primary reason for this observation can be attributed to the temperature gradients measured on the bridge deck from night to noon.