Development of Accurate Bridge Structure Strain Response Function Due to Temperature Changes Effect

Monitoring bridges performance is a vital task to ensure their safety and to plan their maintenance operations. The bridges are affected mainly by the traffic loads and the environmental changes. The bridge behaviour can accurately be monitored with the known traffic loads changes; however, the environmental changes effect is crucial and challenging to monitor. The most significant environmental changes effect is mainly produced by the temperature changes. Therefore, this research investigates the temperature changes effect on the concrete bridge behaviour. The objective of this paper is to develop an accurate bridge stain model to precisely represent the temperature changes effect. The current state-of-the-art method for bridge strain modelling is developed in time domain. This paper proposed a frequency response method for bridge stain modelling where the model is developed in the frequency domain. The frequency-domain response method is significantly preferable than time-domain method because the low frequency band of interest can be easily selected in the modelling and the high frequency band (noise band) can be neglected. To examine the performance of the proposed frequency-domain bridge strain response model, the datasets were collected from strain and temperature sensors installed on the Fu-Sui Bridge, China. The frequency-domain bridge strain response model is developed using the Least Squares Frequency Transform (LSFT). The input to the frequency-domain bridge strain response model is the temperature changes and the output is the static strain data. The results shows that the significant strain response dynamic due to the temperature changes is in low frequency band (0.00 – 0.15 Hz) with the peak value at 0.05 Hz for Fu-Sui Bridge case study. Moreover, the bridge strain impulse response can be accurately developed form the bridge strain frequency response using the Inverse Least Squares Frequency Transform (ILSFT). The significance of the developed impulse response is that it can be convolved with the temperature changes in time domain to estimate the strain response of the concrete structure due to the temperature changes in real-time mode. Consequently, the strain differences between the estimated strains and the measured strains are used to monitor any anomaly that can be interpreted as a sign of fatigue in the concrete structure under investigation.