Case Study on Temperature Effects on Bridge Frequencies

Abstract

Abstract

Understanding the influence of temperature on the natural frequencies of concrete bridges is essential for reliable vibration-based structural health monitoring. Generally, temperature shows a negative correlation with bridge modal frequencies. However, comparative investigations of temperature sensitivity between healthy and damaged bridges remain scarce. In this study, two in-service prestressed concrete bridges of identical design, located at the same site, are analyzed - one in healthy condition and the other with three confirmed tendon breaks caused by a truck impact. Both bridges are instrumented with accelerometers and temperature sensors. Operational Modal Analysis (OMA) is conducted using Frequency Domain Decomposition (FDD) and Stochastic Subspace Identification (SSI) methods. The time lag between temperature variation and modal frequency change is then examined, followed by sensitivity and correlation analyses. Furthermore, the influence of temperature gradients on modal frequencies is evaluated. Results reveal that the damaged bridge exhibits higher temperature sensitivity in its modal frequencies compared with the healthy one. A higher temperature gradient also leads to greater frequency variation. Possible physical mechanisms underlying these observations are discussed. The findings emphasize the importance of damage-state-dependent temperature normalization for vibration-based bridge monitoring and provide valuable insights for long-term modal analysis under varying environmental conditions.