骨料粒径对混凝土动态拉伸强度及尺寸效应影响分析

骨料粒径是影响混凝土力学性能及破坏机理的重要因素。从细观角度出发,将混凝土看作由骨料颗粒、砂浆基质及界面过渡区组成的三相复合材料,考虑细观组分的应变率效应,建立了混凝土动态拉伸破坏行为研究的细观力学分析模型,模拟研究了不同骨料粒径下混凝土动态拉伸破坏行为,并揭示了动态拉伸强度的尺寸效应规律。研究表明:低应变率下骨料不发生破坏,骨料粒径对混凝土动态拉伸破坏模式及拉伸强度影响显著,且拉伸强度的尺寸效应随骨料粒径的减小而削弱;高应变率下裂缝将贯穿骨料,骨料粒径的大小对混凝土动态拉伸强度及尺寸效应影响可忽略。最后,结合应变率效应的影响机制,建立了混凝土拉伸强度的"静动态统一"尺寸效应理论公式,该公式可以较好描述各骨料粒径下混凝土动态拉伸强度与试件尺寸的定量关系。

Influence of aggrecate size on the dynamic tensile strength and size effect of concrete

Aggregate size is an important factor affecting the mechanical properties and fracture mechanism of concrete.From the microscopic point of view, concrete was considered as a three-phase composite material composed of aggregate particles, mortar matrix and interfacial transition zone.Considering the strain rate effect of meso-components, a meso-mechanical analysis model for the study of dynamic tensile failure behaviors of concrete was established.The dynamic tensile failure behavior of concrete with different aggregate size was simulated and the size effect on the dynamic tensile strength was revealed.The results are as follows: at low strain rate, aggregate does not be destroyed, and aggregate size has a significant effect on the dynamic tensile failure mode and tensile strength of concrete.The size effect on the tensile strength weakens with the decrease of aggregate size.Cracks will penetrate aggregate at high strain rate, so that the effect of aggregate size on the dynamic tensile strength and size effect of concrete can be neglected.Finally, combining with the influence mechanism of strain rate effect, a theoretical formula for the “static and dynamic unified” size effect of concrete tensile strength was established, which can well describe the quantitative relationship between the concrete dynamic tensile strength and specimen size under different aggregate size.