箱内边界模拟方法对箱梁截面温度场的影响研究

为准确模拟箱内温度,选择合适的箱内边界条件模拟方法进行箱梁截面温度场研究,以某混凝土箱梁桥为背景,实测其箱梁截面温度场,采用MIDASFEA软件建立箱梁截面模型,分析4种箱内边界条件模拟方法(实测温度法、环境温度法、气温均值法和空气单元法)对箱梁截面温度场的影响,并分析极端温度下箱梁截面的平均温度。结果表明:对于箱梁截面温度日变化曲线,采用实测温度法的有限元计算值与实测值吻合最好,缺乏实测箱内温度时,采用空气单元法的有限元计算值与实测值吻合最好;4种方法对箱梁截面的平均温度及竖向正温度梯度的影响均较小;空气单元法可进行极端温度下的箱梁截面温度场分析。建议采用空气单元法进行混凝土箱梁截面温度场研究。

Research on Influence of Simulation Method of Inner Boundary Condition on Temperature Distributions on Cross-Sections of Concrete Box Girders

In order to accurately simulate the temperature inside the box girders, we researched the temperature distributions on cross-sections of box girders by choosing appropriate simulation methods of inner boundary conditions. Taking a concrete box girder bridge as a study case, we measured the temperature distributions on the cross-sections of box girders on site. Moreover, we developed finite element models of the cross-sections of box girders by using MIDAS FEA software to analyze the influences of four simulation methods of inner boundary conditions (namely, measured temperature method, ambient temperature method, mean ambient temperature method and air element method) on the temperature distributions on the cross-sections of box girders, and analyzed the average temperatures of the cross-sections of box girders under historically extreme temperature conditions. The results indicate that the hourly temperature curves of the cross-sections of box girders calculated using the finite element model by the measured temperature method provide the closest agreement with measured hourly temperature curves. When there is a lack of measured temperature data from the inside of the box girders, the hourly temperature curves calculated using the finite element model by the air element method provide the closest agreement with measured hourly temperature curves. The influence of four simulation methods of inner boundary conditions on the average temperatures and positive vertical temperature gradients on the cross-sections of box girders is negligible. The air element method can be used to analyze the temperature distributions on the cross-sections of box girders under historically extreme temperature conditions. The air element method is proposed to carry out the research on the temperature distributions on cross-sections of concrete box girders.