小半径曲线刚构箱梁桥日照时变温度场与温度效应

应用太阳物理学理论确定了太阳的实时位置, 结合光线跟踪算法实时选取了结构的时变迎光面, 得到了结构的时变热边界条件; 以永顺—吉首高速公路石家寨立交中的一座小半径曲线刚构箱梁桥为工程背景, 参考当地历史气象数据, 以气温最高的某夏日为例, 在考虑太阳辐射、长波辐射、对流换热和风速等环境条件下, 实现了小半径曲线刚构箱梁桥三维瞬态日照时变温度场的有限元仿真, 通过热-结构耦合分析得到了小半径曲线刚构箱梁桥的日照时变温度效应。研究结果表明: 在日照时变辐射作用下, 由于小半径曲线刚构箱梁桥翼缘板的遮盖作用, 箱梁腹板受太阳直射的时间不同, 箱梁各断面腹板处最大温差为1.3℃; 小半径曲线刚构箱梁桥顶板竖向温度梯度变化规律与《公路桥涵设计通用规范》 (JTG D60—2015) 中相似, 顶板上下表面间最大温差为14.3℃, 且箱梁顶板下表面温度变化滞后箱梁顶板上表面约3 h; 小半径曲线刚构箱梁桥顶板下表面会出现最大为3.13 MPa的横向拉应力, 顶板上表面、腹板外表面也均会出现超过2 MPa的横向拉应力; 小半径曲线刚构箱梁桥梁端与跨中位移变化趋势相反, 初步揭示了日照时变辐射作用下小半径曲线刚构箱梁桥的蛇形运动规律。 

Solar radiation time-varying temperature field and temperature effect on small radius curved rigid frame box girder bridge

The real time position of the sun was determined by using the theory of solar physics. Combining with the ray tracing algorithm, the time-varying light surfaces of structure were selected in real time, and the time-varying thermal boundary conditions of structure were obtained. Taking a small radius curved rigid frame box girder bridge in Shijiazhai Interchange of Yongshun to Jishou Expressway as an engineering background, a summer day with the highest temperature was chosen by referring to the local historical meteorological data, and the finite element simulation of three-dimensional transient solar radiation time-varying temperature field of small raduis curved rigid frame box girder bridge was realized with the consideration of solar radiation, long wave radiation, convective heat transfer, wind speed and other environmental conditions. The solar radiation time-varying temperature effect on the small radius curved rigid frame box girder bridge was obtained through the thermal-structural coupling analysis. Research result shows that under the action of time-varying solar radiation, due to the covering effect of flange plate of small radius curved rigid frame box girder bridge, the direct sunlight times of box girder webs are different. The maximum temperature difference at the webs of each section of box girder is 1.3 ℃. The vertical temperature gradient variation law of roof of small radius curved rigid frame box girder bridge is similar to that in the General Specifications for Design of Highway Bridges and Culverts (JTG D60—2015). The maximum temperature difference between the upper and lower surfaces of roof is 14.3 ℃, and the temperature change of lower surface of box girder roof is about 3 h behind that of upper surface of box girder roof. The maximum transverse tensile stress at the lower surface of small radius curved rigid frame box girder bridge roof appears to be 3.13 MPa, and the transverse tensile stresses of upper surface of roof and the outer surface of web also appear to be more than 2 MPa. The displacement change trend of girder end opposites to that of mid-span of small radius curved rigid frame box girder bridge, preliminary revealing a serpentine movement law of small radius curved rigid frame box girder bridge under the action of time-varying solar radiation.