Eliminating environmental temperature and humidity effects on the frequencies of bridges based on co-integration analysis

In vibration-based structural health monitoring, frequency is widely used to judge the occurrence of damage, which is quite efficient and convenient. However, besides damage, variations of environmental factors, such as temperature and humidity can also cause the changes of frequency. To eliminate the effects of environmental factors, co-integration analysis method in the field of econometrics is adopted. First of all, the concept of co-integration analysis is presented. Then dynamic tests on a two-way curved arch bridge and three concrete simply supported model beams were introduced. The frequency, environmental temperature and humidity were recorded every one or 2 hours. After that, co-integration analysis was carried out and the co-integration equation among frequency, environmental temperature and humidity was determined. Finally, the effects of environmental temperature and humidity on the frequency were eliminated by the co-integration equation, which makes the vibration-based structural health monitoring method more accurate and reliable.