超低温下钢筋混凝土钢筋温度约束应力研究

Research on temperature induced restraining stress of steel bar in reinforced concrete under ultra-low temperature

利用自主研发的超低温力学加载试验设备,分别实现对钢筋混凝土受弯和轴拉试件同步施加力以及在0~-165℃范围内的降温作用.研究钢筋混凝土在超低温作用下的抗拉刚度和抗弯刚度随温度的变化规律,以及混凝土与钢筋在超低温条件下因线膨胀系数差异引起的约束内力发展情况.研究结果表明:在0~-100℃内,轴拉试件的抗拉刚度和受弯试件的抗弯刚度变化趋势相似,随温度降低呈非线性增长趋势,在低于-100℃后,两种刚度趋于稳定;随着温度下降,混凝土和钢筋热变形差异会越发显著,并导致在钢筋中产生不可忽略的约束应力,当试件从常温下降到-100℃以下时,其内部的钢筋约束应力更加显著,在设计中应予以重视.

force and cooling effect in the range of 0~-165 ℃ for reinforced concrete bending specimens and axial tensile specimens. The change law of tensile stiffness and flexural stiffness of reinforced concrete with temperature were studied under ultra-low temperature, as well as the development of constrained internal forces caused by the difference in linear expansion coefficient between concrete and steel bar under ultra-low temperature.Research results show that within 0~-100 ℃,the variation trend of tensile stiffness of the axial tensile specimen and the flexural stiffness of the bending specimen are similar,both showing a nonlinear growth trend with temperature decreasing, and then tend to be stable when below-100 ℃ . As the temperature drops, the difference between the thermal deformation of concrete and steel bar would become more significant,leading to the non-negligible restraining stresses in the steel bar. When the test specimen is tested from normal temperature to below-100 ℃, the restraining stress in the internal steel bar is especially significant,which should be taken seriously in the design.