Effects of thermal environment on structural frequencies: Part II - A system identification model

In civil structures such as bridges the changes in vibration characteristics such as modal frequencies are often used to detect damage for structural health monitoring. These vibration characteristics, however, change not only due to structural damage but also due to changes in the environmental conditions such as temperature variations. For structural health monitoring using modal frequencies, it is much desirable to be able to estimate the structural frequencies as a function of structural temperatures which can be conveniently measured. In this paper, we develop an approach to establish this modal frequency and bridge body temperature relationship. The subspace system identification-based approach, combined with input data filtering to capture trends introduced by seasonal changes in the temperature, is used to develop an approach to obtain this bridge body temperature-frequency relationship. Utilizing the simulated data for two types of bridge structures, the approach is exhaustively tested for its reproduction and generalization performances over different thermal regimes that are encountered in practice.