基于扩展离散元法的钢筋混凝土梁裂缝分析方法

针对传统数值模拟方法难以准确模拟钢筋混凝土(RC)梁开裂的问题,提出一种改进的扩展离散元法(EDEM)。该方法引入拉伸-剪切破坏准则,建立六边形块体模型,块体接触处存在潜在裂缝,根据EDEM计算流程,将满足破坏准则的潜在裂缝转化真实裂缝,实现裂缝的模拟。采用该方法建立二维RC梁模型,开展RC梁四点弯曲试验,结合理论计算,对其开裂模式、跨中位移及固有频率变化规律进行对比。结果表明:随着荷载增大,RC梁底部产生裂缝,当裂缝穿过梁宽度方向3/4时,向加载点方向延伸;基于RC梁跨中位移变化和固有频率连续下降的特征,可确定裂缝扩展和纵向受拉钢筋屈服导致的结构刚度降低过程;EDEM数值模拟结果与理论、试验结果基本吻合,该方法可有效模拟RC梁开裂和扩展过程。

Crack Analysis for Reinforced Concrete Girder Based on Extended Discrete Element Method

The conventional numerical simulation methods have disadvantages in accurately simulating the cracking of reinforced concrete(RC)beam.To address this issue,an upgraded extended discrete element method(EDEM)is proposed,in which the tension-shear damage criterion is considered.The model of a hexagonal block that contains potential cracks was established.According to the workflow of EDEM calculation,the potential cracks satisfying the damage principle were converted to real cracks,to realize the crack simulation.The method was used to establish a 2D RC beam model for calculation and four-point bending test was also conducted.The cracking patterns,midspan displacement and variation law of natural frequencies were compared based on the theoretical calculation and test results.The comparison demonstrates that as the increase of loads,cracks occur in the base of the RC beam,and when the cracks keep propagating and go through 3/4 of the girder width,the cracking will turn to extend towards the load-applying point.Based on the midspan displacement variation of the RC beam and the constant dropping of natural frequencies,the decreasing process of the structural stiffness induced by crack propagation and yielding of longitudinal tensile reinforcement can be determined.The results of EDEM numerical simulation are basically consistent with the theoretical analysis and test results,proving that the method can effectively simulate the cracking and crack propagation process of the RC beam.