钢筋混凝土轴压柱长细比效应的细观数值研究

Mesoscopic numerical investigations on the slenderness effect of reinforced concrete column under axial compression

钢筋混凝土柱名义轴压强度的尺寸效应源于:1)混凝土材料本身的非均质性及其力学非线性;2)钢筋/混凝土相互作用的高度复杂性.此外,长细比效应是影响钢筋混凝土柱最终破坏模式及其承载能力的另一重要因素.考虑混凝土材料细观结构的非均质性,及钢筋与混凝土间的非线性黏结滑移等因素,建立了钢筋混凝土柱轴心受压加载下力学行为研究的细观尺度力学分析模型.首先通过反演法确定了混凝土各细观组分的力学参数;进而对不同长细比钢筋混凝土柱在轴心受压加载下的破坏行为进行了数值模拟研究.结果表明:低长细比柱轴压加载下主要发生压剪破坏;而高长细比柱则发生屈曲失稳破坏,且由于端部效应的影响,破坏区域集中于柱的端部;长细比值小于9时,柱名义强度无明显变化,而大于9时,柱的屈曲强度迅速降低.

The size effect of the nominal strength of reinforced concrete columns is caused mainly by 1） the heterogeneity of concrete itself,and2） the complex mutual effects between steel rebar and the surrounding concrete.Besides,the slenderness effect is another brutal factor that could affect the failure pattern and the load capacity of RC columns.Considering of the mesoscopic heterogeneity of concrete and the nonlinear bond-slip behavior between concrete and steel rebar,a meso-scale mechanical analysis model for the study of mechanical properties and failure behavior of RC columns subjected to axial compressive loading is set up.First,the mechanical parameters of the concrete meso components are confirmed by an inversion method based on the simulation of compressive mechanical properties test of a concrete specimen.Then,the damage process of the RC columns with different slenderness ratios subjected to axial compressive loading is simulated.The results indicate that,the RC columns with low slenderness ratios exhibit compression-shear failure under axial compressive loading.The RC columns with high slenderness ratios exhibit buckling failure,and the failure zone concentrates into the ends of the column due to the end effect.The nominal strength pronounces stable value as the slenderness ratio is smaller than 9,and it decreases rapidly when the slenderness ratio exceeds 9.