早龄期混凝土热力学性能差异对应力的影响研究

Influences of differences of concrete thermodynamic performance on concrete stress field at early ages

针对目前对由混凝土热力学性能差异导致的结构温度应力缺乏认知的现状,依据现有理论,定性分析热胀系数差异和自生体积变形差异对混凝土早龄期温度应力的影响,并采用混凝土三维非稳定温度场和应力场有限元方法,对这一影响进行仿真计算和定量分析。结果表明,热胀系数差异和自生体积变形差异是早龄期混凝土结构产生不利拉应力不可忽略的因素,而自生体积变形差异有上下层自生体积变形差和内外自生体积变形差两种类别,其中前一种自生体积变形差主要取决于间歇时间,后一种自生体积变形差由内外层混凝土水化程度不同引起。

At present,few researches are carried out to study the influences of differences of concrete thermodynamic performance on concrete stress field at early ages,therefore we analyze the influences of thermodynamic performance differences,namely thermal expansion coefficient difference(TECD) and autogenous volume deformation difference(AVDD),on concrete stress field qualitatively based on the existed theories,and further conduct simulation and quantitative analysis by the method of 3D-FEM of unstable temperature field and stress field.The results show that TECD and AVDD both have significant influences on tensile stress of concrete at early ages,and the AVDD can be further categorized as upper-lower layer AVDD and internal-external AVDD,the first type AVDD is determined by intervals and the second type is induced by different hydration degree between internal and external concrete.