混凝土拉伸断裂的细观数值分析

根据混凝土试件拉伸和三点弯曲的物理模型,用梁-颗粒模型BPM 2D(B eam-Particle M ode l)模拟了混凝土拉伸和三点弯曲试件微裂纹的萌生、扩展直至试件宏观破坏的全过程。在梁-颗粒模型中用三种类型梁单元形成混凝土细观数值模型,每种类型梁单元的力学性质均按韦伯(W e ibu ll)分布随机赋值以模拟混凝土细观结构的非均匀性。数值模拟结果给出了混凝土拉伸应力-应变曲线和三点弯曲载荷-位移曲线,以及混凝土试件破坏过程最大应力分布图和裂纹扩展图。数值模拟结果显示混凝土破坏过程实际上就是微裂纹萌生、扩展、贯通,直到宏观裂纹产生导致混凝土失稳断裂的过程。通过对数值模拟结果的分析,揭示出混凝土在拉伸条件下裂纹尖端的拉应力集中是裂纹扩展的动力,混凝土组成材料力学性质的非均匀性是造成裂纹扩展路径曲折的重要原因。

Numerical analysis of tensile fracture of concrete at mesoscale level

According to physical model of tensile and three-point bending test,the complete processes from the initiation and propagation of micro cracks to the macroscopic failure of concrete specimen were simulated by BPM2D(Beam-Particle Model).Three types of beam in BPM2D have been used to form numerical model of concrete at mesoscale level and the mechanical properties of every typal beam are randomly allocated according to Weibull distribution to reflect the initial heterogeneity of concrete at mesoscale level.It worked out the tensile stress-strain curve,the load-displacement diagram,the maximal stress distribution figures and the crack history figure during the deformation and failure process of the concrete specimen.The numerical simulation results show that the initiation,propagation and linking each other of crack in concrete samples at mesoscale level produce the macro-failure of concrete samples.Based on the analysis of simulated results,it revealed that tensile stress at the crack tip is the driving force for the crack propagation,and the heterogeneity of mechanical property of material among concrete influences greatly on the curvilinear of crack propagation path.