将混凝土看成粗骨料和水泥砂浆组成的二相非均质复合材料。根据富勒级配曲线和瓦拉文平面转化公式,编写了二维圆形骨料随机分布程序,对混凝土在冲击荷载作用下的动力响应进行了数值模拟。分析冲击速度、试件尺寸、粗骨料大小及分布和粗骨料体积分数对混凝土动态力学性能的影响,讨论了混凝土的冲击破坏模式。数值模拟表明:混凝土的峰值应力随着冲击速度的增大而增大,具有明显的率效应;随着模型尺寸的增大而减小,表现出明显的尺寸效应;随着粗骨料体积分数增大,冲击荷载作用下混凝土的峰值应力呈现先增大后减小的趋势,粗骨料体积分数为40%时混凝土峰值应力最大;保持粗骨料最大粒径不变,随着粗骨料最小粒径的增大,混凝土的峰值应力逐渐减小;保持粗骨料最小粒径不变,随着粗骨料最大粒径的增大,混凝土的峰值应力呈现先增大后减小的趋势。数值模拟结果为混凝土的工程应用提供了理论依据和技术支撑。
With concrete regarded as a two-phase non-homogeneous composite material consisting of coarse aggregate and cement mortar and on the basis of Fuller gradation curve and Walaraven plane conversion formula,a two-dimensional circular aggregate random distribution program of the concrete was designed to simulate the dynamic response of the concrete subjected to impact loading. The influences of impact velocity,specimen dimension,size and distribution of coarse aggregate and volume fraction of coarse aggregate on the dynamic mechanical behavior of the concrete were analyzed,and the impact failure mode of the concrete was also discussed. The regulations of impact velocity,specimen dimension,size and distribution of coarse aggregate and volume fraction of coarse aggregate on the dynamic mechanical behaviors of the concrete were presented. Our numerical simulation shows that the peak stress of the concrete increases with the impact velocity,and thus the concrete is rate-dependent. With the enhancement of the specimen dimension,the peak stress of the concrete decreases,so the concrete produces an obvious size effect. With the volume fraction of coarse aggregate,the peak stress of the concrete increases at first and then declines. When the volume fraction of coarse aggregate equal to 40%,the peak stress of the concrete reaches its maximum value. With the increase of the minimum diameter of coarse aggregate,the peak stress of the concrete declines. However,with the increase of the maximum diameter of coarse aggregate,the peak stress of the concrete increases initially and then declines,which provides a theoretical guidance and technical support for the engineering application of the concrete.