Southwest Jiaotong University
China Postdoctoral Science Foundation (No. 2019TQ0271, 2019M663554), and Project of Science and Technology Department of Sichuan Province (No. 20YYJC4099).
The present study evaluates the temperature effects on a long-span suspension bridge with steel box girder based on the historical temperature data. Firstly, four common probability distribution models are proposed to fit the probability distribution of the daily temperature extremes in different seasons at the bridge location. Five performance indexes are adopted to evaluate the fitting quality of each probability distribution model, with which the optimal probability distribution model is identified. Based on the optimal probability distribution model, the temperature extremes in terms of 20 years, 50 years and 100 years of return periods are computed subsequently. Secondly, the finite element model of a long-span steel box girder suspension bridge is established using ANSYS finite element software. Based on the established finite element model, the effects of temperature variation of different structural components on the natural frequency and displacement are further investigated. Finally, the influence of restraint systems, i.e., central buckle, vertical support, and expansion joint, on the thermal-induced effect of bridges is further studied. The results show that, except for the first-order symmetrical transverse bending frequency, all the other natural frequencies are negatively correlated with the temperature variation. In addition, when the temperature of the pylons and stiffening girders varies within ±25℃, the variation of all the natural frequencies is less than 5%. Nevertheless, when the temperature of the main cables reduces by 12 ℃, the anti-symmetric vertical frequency of the main girder decreases significantly, about 12%. Besides, it is also found that the vertical displacement of the stiffening girder and pylon is linearly correlated with the temperature variation of the entire bridge, and the longitudinal displacement of stiffening girder is mainly controlled by the temperature variation of the stiffening girder. Due to the height difference of the bridge pylon, the longitudinal displacement at two ends of the girder due to temperature variation is different, i.e., the longitudinal displacement due to unit temperature variation at Jianshui end and Yuanyang end is 4.7 mm/℃ and 3.3 mm/℃, respectively. In addition, the vertical displacement and rotational angle of the stiffening girder ends are mainly affected by the temperature variation of the main cable. Finally, the influence of vertical supports and expansion joints on the thermal-induced longitudinal displacement response of the girder is found to be insignificant, while the central buckle is found to have significant effect on the thermal-induced internal forces of short suspenders in the mid-span.