混凝土轴向压缩时不同高宽比试件中的剪切带研究

Research on Shear Bands of Different Width-to-height-ratio Test-pieces During the Course of Concrete Axial-compression

混凝土的抗压强度具有明显的形状效应,其诱发机理是试块端面摩阻力限制了端头水平方向的位移,这种特殊的边界条件改变了试件的破裂路径,最终影响强度测试结果.针对这一现象,以普通单轴压缩为力学模型,基于莫尔-库仑强度准则,分析发生剪切破坏时普通混凝土的剪切带特征.结果表明,4倍高宽比时最危险破裂面不受端头约束的影响,最危险破裂面不受边界影响的临界高宽比为3.21~3.42.高宽比继续减小时,破坏模式逐渐从剪切破坏向压缩破坏过渡,莫尔-库仑准则已不再适用.

The compressive strength of concrete has obvious shape effect, the inducement mechanism of which is that the end face of testing pieces has frictional resistance restraining the horizontal displacement of end, and such special fringe conditions changes their cracking path and affects the strength test result ultimately. Regarding the above phenomena, the article analyzed the shear band feature of normal concrete when the shear failure occurred based on classical Mohr Coulomb Strength Criterion by taking normal uniaxial compression as the mechanical model. The result shows that, the most dangerous fracture surface is unaffected by end constraint when height to width ratio turns to 4：1, and the critical depth width ratio of most dangerous fracture surface unaffected by edge is 3.21- 3.42. The failure mode transfers from shear failure to compressive failure gradually when the ratio of height to width ratio reduces and the Mohr Coulomb Strength Criterion is no longer applicable.