The total volume of concrete casting to the pile cap of 28# main pier in Shanghai-Nantong Yangtze River Bridge is up to 42 000 m3,so the concrete temperature must be controlled during construction.The numerical simulation combining with site condition was carried out to determine the key parameters under direct sunlight in high-temperature summer,such as the maximum adiabatic temperature,the convective heat transfer coefficient of the cooling water pipe and so on,as well as the temperature-time curve of control points.The results show that if the temperature control indexes of concrete in pile cap meet design requirements,then the velocity of cooling water(temperature is about 25℃) is the main engineering measure of temperature control,which should be greater than or equal to 1.5 m/s in 2~3 days after casting concrete.The velocity should be reduced to 1 m/s after the pile cap reaches its peak temperature.The velocity of cooling water could be continuously decreased over time and the changes of internal temperature of concrete.The duration of water cooling is suggested to greater than or equal to 7 days.The results required by numerical simulation can be used to guide mass concrete construction of the pile cap.%建设中的沪通长江大桥28#主墩承台混凝土浇筑量多达4.2万m3,需采取温度控制措施.本文结合现场条件开展数值模拟分析,确定在夏季直晒高温条件下承台混凝土的最大绝热温升、冷却水管对流换热系数等关键参数,以及承台混凝土各控制点的温度-时间曲线.计算结果表明,若使承台混凝土温度控制指标满足设计要求,则承台混凝土浇筑后2~3 d内,作为温度控制主要工程措施的冷却水(温度为25℃左右)流速应≥1.5 m/s;达到峰值温度以后流速降低为1 m/s;随时间和混凝土内部温度变化流速可继续降低;通水降温时长应≥7 d.数值模拟结果可用于指导承台大体积混凝土的施工.
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