| Author: | Wu, Wanglin |
| Title: | Temperature behaviors of a footbridge through integration of field monitoring with numerical simulation |
| Advisors: | Xia, Yong (CEE) |
| Degree: | Ph.D. |
| Year: | 2022 |
| Subject: | Footbridges -- Deteroriation Thermal stresses Structural health monitoring Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xxii, 174 pages : color illustrations |
| Language: | English |
| Abstract: | Bridges are subject to daily, seasonal, and yearly environmental thermal effects induced by solar radiation and ambient air temperature. Temperature variations in bridge components cause movement and usually lead to thermal stress because of the indeterminacy and non-uniform distribution of temperature. Excessive movement and stress may damage the bridge. Bridges are also subjected to other loads such as winds. The temperature action needs to be separated to allow the individual assessment of other loads. Moreover, the varying temperature may have a significant effect on structural responses that must be considered for the reliable detection of structural changes. The traditional thermal analysis adopts a regression model between the temperature and bridge responses or conducts a simplified heat-transfer simulation; both cannot study the accurate quantitative behaviors of the bridge. This PhD study aims to investigate the temperature behaviors of bridges in real-time by integrating field monitoring and advanced numerical heat-transfer simulation. The study uses the structural health monitoring (SHM) system of The Hong Kong Polytechnic University (PolyU) footbridge as the testbed. The three-dimensional (3D) global heat-transfer analysis is first conducted to obtain the temperature distribution of the entire footbridge. The measured air temperature and solar radiation are used as the thermal boundary. The hemisphere technique is adopted to calculate the view factor between different surfaces of the bridge, which are then used to obtain the solar radiation on all external surfaces in different times on different dates. With the global heat-transfer analysis, the temperature data of the entire bridge are computed and have a good agreement with the measured counterparts. The temperature distribution of the bridge obtained in the above step is then input into the same finite element model (FEM) for structural analysis to calculate the temperature-induced bridge responses. The same FEM offers an automatic and efficient structural analysis. In particular, the stresses and displacement of the bridge on a hot and cold days in 2020 are investigated. The calculated and monitored responses are compared and explained. Different load effects, including temperature, pedestrians, winds (maximum mean speed of 5 m/s) and earthquakes (5.2 magnitude at Yulin, over 400 km away from Hong Kong), are also compared. It shows that the temperature-induced stresses are larger than the mean wind-induced stresses. Wind-induced accelerations are similar to pedestrian-induced; both are larger than earthquake-induced vibrations. A touch screen visualization platform integrating research, teaching and public education is established. The platform consists of the configuration and function of the SHM system; real-time measurement data; numerical simulation results of the footbridge under pedestrians, temperature, winds, and earthquakes; and fundamental knowledge in bridges, sensors, and surveying. |
| Rights: | All rights reserved |
| Access: | open access |
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