Vertical temperature gradients of concrete box girder caused by solar radiation in Sichuan-Tibet railway

Abstract

Spatial and temporal temperature variations are critical for concrete box girders, and non-uniform temperature distributions induced by solar radiation depend on the structural shapes and shadows cast on them. There have been many studies of temperature distributions and temperature gradients of concrete box girders, but few have considered a high altitude plateau climatic environment. In this study, the nonlinear temperature distributions of concrete box girders in the Sichuan-Tibet railway caused by solar radiation were investigated based on experimental analysis, real-time shadow-selection algorithm, and finite element method. Furthermore, a vertical temperature gradient model of the concrete box girders was obtained. The vertical temperature gradient values first rise, then decrease, and finally rise again from Chengdu to Lhasa, with samples forming a normal distribution. The recommended vertical temperature gradient value was 25 °C with a confidence interval of 95%. This provides a reference for the design and maintenance of concrete box girders on the Sichuan-Tibet railway.

摘要

目的

1. 分析川藏铁路沿线不同地理区域混凝土箱梁的温度梯度变化规律;2. 确定川藏铁路混凝土箱梁的温度梯度建议值。

创新点

1. 基于川藏铁路加查2号桥现场试验,分析了太阳辐射作用下箱梁时变温度场特征,并基于有限元日照仿真模型成功地模拟了试验结果;2. 提出了川藏铁路混凝土箱梁的竖向温度梯度模式,分析了藏铁路沿线不同地理区域混凝土箱梁的温度梯度值变化规律;3. 基于一定的置信区间,给出了川藏铁路混凝土箱梁温度梯度建议值,并与现行公铁路桥梁设计规范进行了对比分析。

方法

1. 运用计算机图形学、太阳能工程学、有限元和传热学,开发太阳辐射作用下混凝土箱梁时变温度场分析模型;2. 基于川藏铁路加查2号桥现场试验,分析混凝土箱梁时变温度场特征并验证所开发模型准确性;3. 基于概率统计模型,给出一定置信区间下川藏铁路混凝土箱梁温度梯度建议值。

结论

1. 基于现场试验和有限元仿真,所开发的太阳辐射时变作用分析模型能准确模拟箱梁不均匀温度分布特征。2. 川藏铁路自成都至拉萨,混凝土箱梁竖向温度梯度值整体呈先上升,再下降,最后再上升的趋势; 温度梯度统计样本服从均值23.36 ^oC和方差0.84的正态分布。3. 川藏铁路混凝土箱梁95%置信区间下的竖向温度梯度建议值为25^oC,为川藏铁路混凝土箱梁的设计和养护提供了参考。