低温灌注条件下钢管混凝土水化热应力试验研究

Experimental study on hydration thermal stress of concrete-filled steel tube at low temperature

为研究青藏高原地区低温环境下钢管混凝土拱肋混凝土灌注后水化放热温度分布及温度效应,以川藏铁路拉林段雅鲁藏布江特大桥以工程背景,采用恒温实验箱进行低温环境的模拟,对与实桥同尺寸的1.6 m管径的钢管混凝土构件进行长期连续温度场监测试验。引入等效龄期对低温条件下核心混凝土水化放热规律、混凝土应变时程变化、管内混凝土水化温度分布及温度效应计算方法进行研究。研究结果表明:掺入外加剂的混凝土具有约4 h的水化诱导期,该诱导期对混凝土温度及热应力的变化影响较大;混凝土水化结束后纵向与径向具有较大的残余应变,对合龙温度影响较大;引入等效龄期的双曲线式水化放热模型能够较好地反应钢管混凝土水化温度分布规律;水化温升加快管内混凝土力学性能的发展,使得管内混凝土产生较大的径向与环向应力,计算水化温度效应应计入温度对混凝土力学性能的影响;水化温度应力控制应着眼于降温初始阶段。

In order to study the distribution and effect of hydration and exothermic temperature of concrete-filled steel tubular arch rib under low temperature environment in Qinghai Tibet Plateau,taking the Yarlung Zangbo River Bridge as the background,the temperature field of CFST members of the same size as the real bridge was monitored and tested.The equivalent age was introduced to study the law of heat release,the change of strain time history,the distribution of hydration temperature of concrete in the pipe and the calculation method of temperature effect.The results show that the concrete with admixtures has a hydration induction period of about 4 hours,which has a great influence on the change of concrete temperature and stress.The concrete has a large residual strain in the longitudinal and radial direction after hydration,which has a great influence on closure temperature.The hyperbolic hydration exothermic model with equivalent age can better reflect the hydration temperature distribution of CFST.The increase of hydration temperature accelerates the development of the mechanical properties of concrete in the pipe,which makes the concrete in the pipe produce larger radial and circumferential stress.The influence of temperature on the mechanical properties of concrete should be included in the calculation of hydration temperature effect.The control of hydration temperature stress should focus on the initial stage of cooling.