大跨桥梁结构三维日照温度场计算方法

Computational method for 3D sunshine temperature field of long-span bridge structures

为了研究桥梁结构的三维日照温度场及其效应,基于计算机图形学理论中的光线跟踪技术和空间剖分技术,提出了三维复杂结构表面日照阴影的快速识别方法,在此基础上又基于传热学理论和有限元理论提出了大跨桥梁结构三维日照温度场的模拟方法.最后以某大跨混凝土连续箱梁桥为例,对该方法进行了验证,并对大跨混凝土连续箱梁桥的三维日照温度场进行了分析.结果表明:大跨混凝土连续箱梁桥的悬臂板并不能为其腹板提供有效遮挡,悬臂板遮挡的影响深度约等于悬臂板长度,在影响深度范围之内腹板表面温度基本呈线性变化,而在影响深度之外温度基本不变;顶板上下表面和底板下表面的温度在桥梁纵向上的温差很小,但底板内表面温度在桥梁纵向上的温差较大,可达5.3℃.该方法可为大跨桥梁结构的日照温度效应的更准确计算提供依据,同时也可对大跨桥梁结构响应中的温度效应进行更精确的分离.

In order to study the three-dimensional (3D) sunshine temperature field and its effect on bridge structures,a quick identification method for the sun shadow on the surface of complex 3D structures is proposed based on the ray-tracking technology and space segmentation technology in the computer graphics theories.And then,a simulation method for calculating the 3D temperature field of long-span bridge structures is proposed based on the heat transfer theory and finite element analysis.Finally,by taking a long-span concrete continuous box girder bridge as an example,the simulation method is verified and the 3D sunshine temperature field of the long-span concrete box girder bridge is analyzed.The results show that the cantilever slabs of the long-span concrete box girder bridge are not long enough to protect the web from the solar radiation,and the depth of shielding effect is nearly equal to the length of cantilever slab.Within the depth of shielding,the temperature of the web surface basically changes in a linear fashion,while outside the depth of shielding,there is no change in temperature.The temperature difference between the deck slab and outer surface of the bottom slab in the longitudinal direction of the bridge is small,while the temperature difference of the inner surface of the bottom slab along the longitudinal direction of the bridge is large,which can reach 5.3 ℃.It can provide a basis for more accurate calculation of the sunshine temperature effect on long-span bridge structures,and the temperature effects on structural responses of the long-span bridge can be separated more precisely.