大温差作用下矩形渡槽横截面温度梯度分析

Temperature gradient analysis of rectangular aqueduct transverse section under the effect of large temperature difference

  • 摘要: 渡槽在服役期间经历长期变温差循环作用,势必引起渡槽混凝土产生微裂纹等劣化,降低渡槽安全性。渡槽设计无专门规范,相关规范对渡槽是否考虑温度荷载也无明确指导意见。以新疆某矩形渡槽为例,通过有限元软件计算渡槽横截面温度场,分析其分布规律,探讨渡槽温度梯度及不同桥梁设计规范在渡槽设计中的适用性。研究表明:该渡槽通水时夏季横截面最大竖向正温差为35.8 ℃,不通水时为24.5 ℃;冬季通水时最大竖向负温差为−11.5 ℃,不通水时为−7.8 ℃。渡槽横向最大正温差为18.5 ℃,最大负温差为−8.4 ℃;较大的竖向与横向温度梯度会产生较大的温度应力,在设计中应给予考虑。实例竖向温度梯度与各种桥梁规范推荐的竖向温度梯度模式形式相似,但特征值存在较大差异,桥梁规范中的温度梯度模式不宜直接应用于渡槽温度应力分析,渡槽温度场宜根据槽身结构形式和运行工况计算确定。

     

    Abstract: During the operation period, the aqueduct experiences the cyclic fatigue effect of temperature variation for long term, which may cause the deterioration of the concrete of the aqueduct, such as micro-crack, and gradually reduce the safety degree of the aqueduct. There is no specific design code for aqueduct design, and other relevant design codes don’t provide clear guidance on whether to consider thermal effects for aqueduct. Taking a rectangle aqueduct in Xinjiang as an example and through the finite element software, the aqueduct temperature field is obtained and its distribution law is analyzed. Furthermore, the applicability of vertical temperature gradient pattern recommended by bridge codes in aqueduct design is discussed. The results show that the maximum vertical positive temperature difference in summer is 35.8 ℃ when the aqueduct is running, and 24.5 ℃ when the aqueduct is not running. In winter, the maximum vertical negative temperature difference is −15.1 ℃ with running water, and −7.8 ℃ without running water. The maximum transverse positive temperature difference of the aqueduct is 18.5 ℃ and the maximum transverse negative temperature difference is 11.2 ℃. Large vertical and transverse temperature gradient will produce large temperature stress, which should be taken into account in design. The vertical temperature gradient of the example is similar to the vertical temperature gradient modes recommended by various bridge codes, but there are large differences in the characteristic values, indicating that the temperature gradient modes of bridge codes may not be directly applied to the temperature stress analysis of the aqueduct. The temperature field of aqueduct should be calculated and determined according to the structural form and operation conditions of the aqueduct.

     

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