各国规范下混凝土箱梁水化热温度作用研究

Research on the Temperature Effect of Hydration Heat on Concrete Box Girders under National Standards

水化热引起的温度变化往往会导致混凝土梁桥早龄期混凝土桥面开裂,甚至在通车前就出现裂缝。为了确保结构的耐久性,对王家河大桥进行了大规模温度测量,并在3种常用水化热模型的基础上进行精细有限元模型分析,两者结合以确立适用于高寒大温差地区的水化热模型,获得空间连续的桥梁温度场,并为相似地区桥梁建设提供参考。结果表明:(1)通过水泥水化热模型计算的王家河大桥测点最大温升为37.2℃,最大里表温差约45℃,最大降温速率约5℃/d,最大温升值在规范限值内(50℃),里表温差(25℃)及降温速率(2℃/d)均超出规范限值,存在开裂风险;(2)本桥计算中指数式最大温升、里表温差、降温速率均比其余两式计算结果更不利,且三者温度演变规律基本一致,而指数式计算参数更为容易,故建议使用指数式进行混凝土箱梁设计;(3)大体积混凝土冬季施工建议使用低热或中热型水泥,并严格控制入模温度、拆模时间以预防温度裂缝的产生。

Hydration heat can cause premature concrete deck cracking in beam bridges before traffic even begins.To ensure structural durability,temperature measurements were taken on the Wangjiahe Bridge and a fine FEM analysis was conducted using 3 hydration heat models.This combo resulted in a model suitable for high-cold&large temp diff areas,providing a continuous bridge temp field.Results showed:(1)Max temp rise was 37.2°C,but within spec limits(50°C).Max temp diff&cooling rate exceeded spec limits,increasing crack risk.(2)Exponential formula had more unfavorable results than the other 2 formulas,but their temp evolution laws were similar.Exponential formula parameters were simpler,so it's recommended for box beam design.(3)It's recommended to use low-or medium-heat cement for winter mass concrete construction&strictly control pouring temp&demo time to prevent temp cracks.