环境降温对斜拉桥混凝土主塔早期开裂影响研究

为了研究环境降温作用对混凝土主塔早期开裂的影响,通过求解热传导方程推导出降温作用下主塔塔壁的温度分布公式,进而通过分析混凝土早期弹性模量、徐变影响,导出计入时变效应的塔壁表面温度应力计算公式。得到反映环境降温作用的温度～时间、应力～时间关系曲线。结果表明:环境降温作用将导致塔壁表面产生拉应力,应力值大小与塔壁内外表面放热系数、塔壁厚度、混凝土水化热、环境降温值、降温起始及持续时间等因素密切相关;上述因素偏不利时,会引发混凝土主塔开裂。

Effect of Cooling on Early-age Cracking in Concrete Tower of Cable-stayed Bridge

In order to analyze the effect of cooling on early-age cracking of concrete towers of cable-stayed bridges, the formulas of temperature distribution of the tower walls are deduced by heat exchange equations, and the formulas of thermal stress of tower surfaces are put forward considering variation of elastic modulus and creep of early age concrete. Then the graph of the relation between temperature and time as well as the relation between stress and time is drawn, which shows the effect of cooling. The results shows that cooling will bring tensile stress to tower surfaces, the value of stress relates to thermal diffusivity of inside and outside of tower walls, thickness of tower walls, hy- dration heat, the drop in temperature, the time when cooling starts and its duration. When the effects of factors above are on the side of disadvantages, cracking will happen.