Evaluation of the effect of ambient temperature on the natural frequency of bridge structures (Case study: Tehran)

In many bridge health monitoring systems, the change in natural frequency is considered as an important warning for the existence or initiation of damage in the structure. Meanwhile, the ambient temperature can have a significant effect on the natural frequency of the bridge. If the investigated bridge is located in an area with extreme temperature changes, the measured natural frequency may show different values at different times and thus cause errors in the damage detection system. This issue reveals the necessity of studying and investigating the effect of temperature on the natural frequency of bridges in different geographical regions with different climates. This article studies the effect of temperature on the natural frequency of bridges in Tehran metropolis. In this regard, the natural frequency of three steel bridges in the city and one concrete bridge located on highway Road in the outskirts of the city was measured during one year and at different hours of the day and night. To do this, the sensors embedded in smartphone and a sensitive accelerometer were used. In the next step, the frequencies obtained from the experiments were analyzed and studied statistically. Examining the results showed that the environmental temperature changes in Tehran can cause frequency changes of about 12% for steel bridges and frequency changes of about 0.5% for concrete bridges. The results of this research show that considering the effect of temperature in health monitoring systems based on modal information for bridges with steel materials is much more important than existing concrete bridges in Tehran.