基于断裂力学与微观机理的钢结构构件和节点断裂评定技术研究

Strictly speaking, the structural components and connections of steel structure are always working with defects, which can be cracks, crack-like defects, or construction and fabrication defects. Under some particular environment and physical effect, most of the flawed structural components and connections will suffer brittle fracture, but the traditional mechanics cannot facilitate the fracture assessment for those flawed components and connections. Besides, the existing fracture assessment method of the steel structures with defects can be just employed for the structural components with single crack or single crack simplified from uncomplicated defect. For the connections and structural components with multiple cracks or complicated defects, the unified fracture assessment method is still unavailable among all those existing methods. Based on the fracture mechanics and micro-mechanics model, this program associates the experimental study, numeric simulation with theoretical analysis to systematically study the fracture assessment technique of the flawed steel components and connections. Firstly, the parameters of the dynamic fracture roughness and the micro-mechanics model will be tested for the materials and connections of the steel structure, and the fracture performance of the constructional details and connections of the welded steel structure will be experimentally study. Then, numeric method for the fracture and damage simulation of the structural components and connections, which can consider the single crack and multi-crack coupling, will be developed. Finally, a set of experimentally and numerically verified fracture assessment method for structural components and connections of the steel structures with strong generalizability and more accuracy will be provided. The achievement of this program will produce the great theoretical significance and engineering application value for the fracture evaluation of the components and connections of the steel structures with crack or crack-like defect, and for the latter repair and reinforcement of those flawed steel structures in engineering practice.

钢结构构件和节点严格来说通常是带缺陷工作的，缺陷可能是裂纹、类裂纹、或者构造与加工缺陷。在特定环境或作用下，带缺陷的钢结构构件和节点往往发生脆性破坏，而传统的力学理论却无法对含缺陷构件和节点进行断裂评定。现有的含缺陷钢结构断裂评定方法，仅适用于钢构件含单裂纹或可以简化为单裂纹的简单缺陷，而对于钢结构节点或含多裂纹或复杂缺陷的钢构件则缺乏统一的断裂评定方法。本项目基于断裂力学和微观机理理论，采用理论分析、试验研究和数值模拟相结合的方法，系统地研究钢结构构件和节点的断裂评定技术。首先对钢结构材料和连接的动态断裂韧性和微观断裂模型进行试验测试；并对钢结构焊接构造和节点的断裂与损伤性能进行试验研究；然后建立考虑单个缺陷和多个缺陷耦合的钢构件和节点断裂与损伤数值模拟方法；最后建立统一的钢结构构件与节点的断裂评定技术。

为了保证带缺陷工作钢结构的安全需求，本项目基于断裂力学和微观损伤机理，系统地研究了钢结构构件和节点的断裂评定技术。针对常用建筑钢材，通过试验手段测定了其动态断裂韧性参数，校正了单调和循环微观损伤模型参数以及材料的力学本构模型；探索了考虑多裂纹耦合扩展的焊接细节疲劳损伤与断裂数值模拟方法，分析了冲击荷载作用下含裂纹缺陷钢构件的动态断裂安全性能；进行了钢框架焊接构造和梁-柱节点的断裂性能试验研究，建立了相应的基于微观机理的抗断性能数值模拟方法；最后，提出了基于SINTAP-FAD方法的含缺陷工作钢结构构件的安全性评定方法和流程。. 本项目研究积累了宝贵的结构钢材动态断裂韧性数据和微观损伤模型参数，提出的多裂纹耦合扩展和节点断裂寿命预测数值模拟方法，为含缺陷工作钢结构构件和节点的安全评估与运营维护提供了坚实的数据保障和技术支撑，具有重要的工程实践意义和学术参考价值。