FRP-混凝土三点受弯梁损伤粘结模型有限元分析

NUMERICAL MODELING FOR COHESIVE FRACTURE OF FRP-CONCRETE BONDED INTERFACES IN THREE-POINT BEND BEAMS

该文采用双线形损伤粘结模型研究带切口FRP-混凝土三点受弯梁(3PBB)I型加载下的界面断裂性能。通过有限元参数分析,详细讨论了界面粘结强度、界面粘结能、混凝土抗拉强度、混凝土断裂能对3PBB受力性能的影响。数值模拟表明,FRP-混凝土界面有两种破坏形式,包括FRP-混凝土界面的损伤脱粘和界面混凝土的损伤脱粘破坏,与实验所观察到的现象一致。两种破坏形式尽管在宏观上均表现为界面脱粘,但破坏机制却不同。FRP-混凝土界面的损伤粘结模型与混凝土的拉伸塑性损伤模型相结合,不但再现了3PBB的宏观力学性能,数值分析得到的荷载-位移曲线接近实验结果,而且还能详细展示FRP-混凝土界面的损伤、断裂破坏过程以及损伤在FRP-混凝土界面和界面混凝土之间的转移,能够预测构件的承载力,有助于界面优化设计,这是单纯以能量判据预测裂纹发展的经典断裂力学方法所无法做到的。

A bilinear damage cohesive zone model is used to simulate Mode-Ⅰ fracture of FRP-concrete bonded interfaces in three-point bending beam （3PBB） specimens. The relationships among the interface cohesive strength, the concrete tensile strength and the fracture energy are discussed in detail through a numerical finite element （FE） parametric study. The results of FE simulations show that there is a transition in the failure mechanism between the debonding of the FRP-concrete interface and the cracking in the interfacial concrete layer near the interface. Such a transition cannot be explained by a fracture-mechanics approach to the crack propagation which only uses an energy criterion for fracture. By combining a damage cohesive law model for the interface and a plastic-damage model for the concrete, the essential features of the transition in failure mechanism are captured. The cohesive damage models for the interface and the concrete combined with the numerical finite element simulation presented in this study can be used to analyze the interface fracture process, predict the load- carrying capacity and ductility, and optimize the interface design.