太阳辐射作用下拱桥温度场研究

Study on the thermal field of arch bridge by solar radiation action

采用ASHRAE晴空模型,利用光线追踪算法编制了基于ANSYS有限元软件的子程序,首次在拱桥温度场计算中实现了太阳辐射、空气对流、长波辐射等环境温度荷载的自动施加。通过与2010年11月7日位于东经108°53′、北纬32°30′的某上承式拱桥现场照片进行对照,验证了该算法可以准确模拟拱上主梁对拱箱的遮盖作用。利用有限元法对该拱桥在当天环境温度荷载作用下,拱上主梁、拱箱的温度场进行了分析。结果表明:在太阳辐射作用下上承式拱桥温度场分布是不均匀的;主梁对拱箱的遮盖作用会导致拱箱温度场分布不均匀,被遮盖位置的温度比太阳直射处温度低;拱桥温度场随太阳辐射强度变化而变化,太阳辐射强度在下午三点时最大,此时刻拱箱顶板上下表面最大温差达到18.5℃。

An automatic load-apply method in thermal simulation is implemented. The solar radiation, air convection, and long wave radiation environment temperature is considered by ANSYS APDL and ASHRAE clear sky model and the ray-tracing algorithm are included in this method. The effectiveness of the algorithm has been verified by comparing with the real pictures of an upper bearing arch bridge on November 7, 2010, in 108 ° 53 ' E, 32 ° 30 ' N. After that, the thermal field of main grider and arch rib in this arch bridge of that day is analyzed by transient FEM analysis. It is established that the thermal distribution of upper bearing arch bridge by solar radiation action is nonuniform. The temperature of areas covered by main grider is lower than that is uncovered. The arch temperature changes over the intensity of solar radiation, the maximum radiation intensity comes at three o'clock in the afternoon, and the maximum temperature difference between top and bottom of rib can reach 18.5℃.