轴压加载下高强钢筋混凝土柱尺寸效应试验研究

EXPERIMENTAL STUDY ON THE SIZE EFFECT OF HIGH-STRENGTH RC COLUMNS UNDER AXIAL COMPRESSION

钢筋混凝土构件的尺寸效应主要是:1)混凝土材料本身的非均质性和力学非线性;2)钢筋/混凝土相互作用的高度复杂性共同导致的。随着建筑结构尺寸不断变大,高强混凝土的应用越来越广泛,其高脆性使得其尺寸效应行为更加明显。此外,钢筋混凝土构件大多处于复杂加载条件下,进而使得其尺寸效应问题变得尤为复杂。该文设计了最大截面尺寸为800 mm×800 mm的16组几何相似高强钢筋混凝土柱,对其在轴向受压单调加载及循环重复加载下的力学行为进行了试验研究,并对其名义轴压强度的尺寸效应进行了分析。结果表明:1)高强钢筋混凝土柱的破坏模式受到加载模式的显著影响;2)随试件尺寸变大,高强钢筋混凝土柱耗能能力减弱;3)较单调加载情况,轴向受压循环重复加载下高强钢筋混凝土柱的破坏表现出更强的脆性,且名义轴压强度减小,尺寸效应更显著;4)Ba?ant提出的"尺寸效应律"能够较好地描述大尺寸高强钢筋混凝土柱名义轴压强度的尺寸效应规律。

The size effect of reinforced concrete（RC） members is mainly caused by： 1） the heterogeneity and the mechanical nonlinearity of concrete; 2） the complex mutual effect between steel rebar and the surrounding concrete. The use of high-strength concrete（HSC） is getting increasingly popular as the structural dimension increases, which in turn makes the size effect behavior more and more obvious. Moreover, the majority of RC members are under complex loading conditions, which makes the size effect more complicated. Experiments on a total of 16 geometrically similar high-strength RC columns with the maximum cross-sectional size of 800 mm× 800 mm were conducted. The mechanical behavior of the high-strength RC columns subjected to axial monotonic and repeated cyclic compressive loadings were studied and the size effect on axial compressive strengths was analyzed. The results indicate that： 1） the failure patterns are closely associated with the loading pattern of the high-strength RC columns; 2） as the dimension of the high-strength RC columns increases, the ductility is getting stronger, however, the energy dissipation capacity is getting weaker; 3） the nominal compressive strengths of the high-strength RC columns obtained under repeated cyclic compression are slightly lower and have a smaller discreteness degree than the ones subjected to monotonic compressive loading, and the size effect is more obvious; 4） the test observations indicate that the bi-logarithmic plot of nominal compressive strengths for large-scale high-strength RC columns follows closely the ＂size effect law（SEL）＂ proposed by Ba？ant.