大型地下广场下沉式顶板的温度应力及保温设计

为研究下沉式地下结构顶板在温度变化作用下应力分布规律及保护措施,对某下沉广场顶板在季节温差和不同季节日温差作用下、结构设置和不设置变形缝情况下的应力和变形情况进行了数值模拟。结果表明:温差作用下,无论是否设置变形缝,结构均会在板梁相交处产生超过混凝土极限抗拉强度的拉应力,设置变形缝对温度应力影响不大;顶板受力和位移中,温度作用所占比重在日温差最不利工况中分别为33%和78.9%,季节温差最不利工况中分别为24.2%和98.7%,应采取加强配筋、保温防裂等措施。通过改变结构顶板上表面的温度,得到了结构上表面所配钢筋数目线性递减的规律,建议下沉结构顶板应以上表面温度为5 ℃作为控制基准设置保温层。

Study on Temperature Stress and Insulation Measures for Sinking Roof of Large Underground Structure

The stress and deformation of large sinking square structure with or without deformation joints caused by the difference in temperature of the day or the season were studied with numerical simulation.The analysis results show that:under the temperature difference, the stress will be so large that the largest tensile stress at the intersection of plates and beam is always beyond the limited tensile strength of concrete; the deformation does little on improving the capability of the sinking plate. The simulation results also show that the influence of the temperature action is great on the structure stress and deformation, the stress and deformation by the difference in temperature of the day are 33% and 78.9%, and by the difference in temperature of the season are 24.2% and 98.7%, so some measures such as reinforcing steel bar and thermal insulation layer against cracking should be taken.In addition, based on the study of various temperature on sinking roof, it is concluded that the number of reinforcing steel bars would change little when the temperature is between 4 ℃~6 ℃,so it is suggested that 5℃at the sinking roof of the large underground integrated structure should be taken as the standard when thermal insulation layer is used.