Investigation of the influence of temperature variations on the modal characteristics of a composite bridge based on strain measurements

Structural Health Monitoring is a contemporary topic for our civil structures and with the evolution of computer-based systems a wide range of modern detection techniques have been developed. Vibration-Based Monitoring (VBM) is one of the most used. The aim of VBM is to find modal features which are highly sensitive to damage and that are as insensitive as possible to environmental and operational influences, since those factors can completely mask the presence of damage. This thesis presents the results of the investigation on the effects of temperature change on the modal characteristics of a FRP composite footbridge. The bridge was monitored with Fiber-Bragg grating (FBG) sensors in order to perform a strain based operational modal analysis. From the results it has been found that frequency and temperature variations have a slightly negative correlation, meaning that with the increase of temperature frequency tends to decrease. Strain mode shapes instead seem to be independent from temperature gradients.