混凝土复合型裂纹扩展的非局部近场动力学建模分析

摘要

基于非局部近场动力学理论,构建了修正的能反映混凝土宏观拉压异性和断裂特征的近场动力学本构模型,开发了相应的离散、加载和时间积分算法,实现典型混凝土构件中复合型裂纹扩展过程模拟.在物质点对尺度上定义局部损伤并考虑物质点对的相对转动,通过求解时空微-积分方程实现裂纹的自然萌生与扩展,避免裂尖不连续带来的求解奇异性、网格依赖性和网格重构以及常规近场动力学本构模型的泊松比限制.通过含单边和双边初始裂纹四点剪切混凝土梁裂纹扩展破坏全过程模拟,得到破坏形态、破坏荷载以及完整的荷载-裂纹开口滑移曲线,并与试验和其他数值模拟结果对比,验证了模型的精确性和算法的稳定性.%An extended non-local peridynamic model and corresponding numerical approach are proposed for the simulation of concrete fracture.The difference in mechanical behavior of concrete under tension and compression,as well as the microscopic effect of long-range forces were introduced into the peridynamic constitutive model,and corresponding discretization,loading and time-integration algorithms were developed.The damage of materials was defined locally at the bond scale,and the rotation of bonds of material points were taken into account so as to eliminate the limitation on Poisson''s ratio when using the common bond-based peridynamic constitutive model.Cracks initiate and propagate naturally by solving the integral-type equations of motion without any re-meshing or crack tip singularity.The proposed modified peridynamic model and numerical approach were validated by simulating the mixed-mode crack problems in single-side and double-side notched concrete beams subjected to four-point shearing loads,and comparing the results including the failure mode,pick load and the complete load-CMSD (crack mouth sliding displacement) curves with experimental observations and other numerical results.