Investigating the Combined Effects of Temperature and Humidity on the Dynamic Properties of Concrete Beams

The dynamic response of structures can be significantly affected by environmental actions. Changes in natural frequencies and damping ratio due to the variation of temperature and humidity is widely recognized but not yet fully understood. Moreover, the performance of various passive control systems and the reliability of structural health monitoring systems can significantly be altered by the lack of understanding of the influence of hygrothermal actions on the dynamic response. In this paper modal hammer tests have been conducted on concrete beams with different strengths in a controlled environmental chamber for various temperatures and a constant range of relative humidity. The results showed that the first three frequencies decreased, as the temperature increased from -10°C to 30°C. The results of an optimization algorithm also were used to extract the dynamic modulus of elasticity and the loss factor. While the former showed a drop, the latter increased for the same range of temperature. Interestingly, different mix designs have manifested different sensitivity to thermal changes.