基于细观力学的混凝土劈拉破坏率相关特性研究

提出了一种高效的混凝土细观力学预处理方法,其中包括基于背景网格的骨料投放与细观三组分的识别;建立了颗粒离散元的混凝土细观力学模型。利用该模型对不同应变率下混凝土的劈拉试验进行了数值仿真,仿真结果显示出的混凝土动力强度提高的规律以及不同应变率下混凝土的破坏模式与试验结果吻合较好。研究表明,随着应变率的提高,混凝土破坏时产生更多弥散状分布的裂纹,同时有些裂纹穿过强度较高的骨料,导致混凝土在高应变率破坏过程中消耗更多的能量,是混凝土的动力强度提高的重要原因。此外,在高应变率下,力链产生更多的分叉,空间分布的不均匀性和随机性增加,因此,在高应变率下混凝土动力强度表现出更大的离散性。

Study of dynamic behavior of concrete under splitting tensile tests based on mesomechanics

By using the particle discrete element method, a three-phase (aggregate, mortar and interface) meso-scaled concrete model is developed for investigating dynamic behaviour of concrete materials with an efficient pre-processing approach. Based on the presented model, the dynamic splitting tensile tests of concrete with different loading rates are performed by numerical simulation. The dynamic increasing factor (DIF) and failure patterns of concrete sample with different strain rates are obtained, which match quite well with the experimental results. The research indicates that, the higher the strain rates, the more cracks there are, which become reticular formation as well. Some of the cracks even penetrate the aggregates. Therefore, this process might require more energy comparing with the static process, which, in a sense, explains the higher strength of concrete in dynamic process. Further more, the force chain bifurcates at high strain rates; and the randomlity and nonuniformity of space distribution increase; consequently the dynamic strength of concrete has a stronger discreteness.