基于断裂理论的在役钢筋混凝土桥梁疲劳损伤机理研究

Concrete bridges account for more than 90% of the total number of domestic bridges, most of them are gengrally at a long-term overload operation state and have seriously hidden danger, whick are the working emphasis of domestic bridge maintenance management in this stage. The existing concrete bridge assessment method failed to grasp the nature of structural fatigue damage, the test content and assessment indicators can not effectively reflect the structure fatigue state, which result in a brittle collapse of the concrete bridge in the past five years are common, even some concrete bridges still brittle collapse in a few years after reinforcement. In view of this, the project makes the reinforced concrete bridge as a breakthrough, further study the fatigue damage mechanism of concrete bridges based on the fracture theory. Study the expansion process of the internal cracks of concrete under fatigue loading, analyze the affections of all cracks general distribution and main cracks propagation to the concrete fatigue property. Study the fatigue slipping performance of the interface between steel-bar and concrete at splitting section, analyze the impact of the slipping length on the beam fatigue performance. Propose a concrete bridge safety assessment method based on fatigue state. The achievements of this paper will promote the domestic bridge maintenance management work on basic theoretical level, which have great practical significance and economic values.

混凝土桥梁占国内桥梁总数的90%以上，普遍处于长期超载运营状态、存在较重的安全隐患，是现阶段国内桥梁管养工作的重点；而现有混凝土桥梁安全评定方法没能抓住结构疲劳破坏的本质，其检测内容和评定指标均不能有效反映结构的疲劳状态，造成了近五年内混凝土桥梁脆性坍塌事故屡见不鲜，甚至出现混凝土桥梁在加固后几年内仍发生脆性坍塌的案例。鉴于此，本项目以钢筋混凝土桥梁为突破口，基于断裂理论展开对混凝土桥梁疲劳损伤机理深入研究。重点研究混凝土内部裂纹状态在疲劳荷载作用下的扩展过程，分析裂纹总体分布和主裂纹扩展状态对混凝土疲劳性能的影响；研究开裂截面处钢混粘结面疲劳滑移性能，分析钢筋滑移长度对梁体疲劳性能的影响；并提出基于疲劳状态的混凝土桥梁安全评定方法。本项目的研究成果将在基础理论层面上，对国内日趋严峻混凝土桥梁管养工作起到推动作用，具有重大的现实意义和经济价值。

混凝土桥梁占国内桥梁总数的90%以上，普遍处于长期超载运营状态、存在较重的安全隐患，是现阶段国内桥梁管养工作的重点；而现有混凝土桥梁评定方法没能抓住结构疲劳破坏的本质，其检测内容和评定指标不能有效反映结构的疲劳状态，造成了近五年内混凝土桥梁脆性坍塌事故屡见不鲜，甚至出现混凝土桥梁在加固后几年内仍发生脆性坍塌的案例；鉴于此，本项目以钢筋混凝土桥梁为突破口对混凝土桥梁疲劳损伤机理进行深入研究。本项目进行混凝土试件抗压疲劳试验，验证了混凝土疲劳应力限值，随着混凝土疲劳应力幅值的增大，混凝土疲劳性能有所衰减；并对混凝土裂纹扩展过程进行了数值仿真分析，分析结果与既有混凝土断裂性能相一致。完成了钢筋与混凝土粘结力测试试验，通过实测钢筋内的拉应力分布和钢筋自由端的变形情况，获得了钢筋与混凝土的平均滑移剪应力，并建立了剪应力随钢筋锚固深度的分布曲线；最终，基于断裂理论对一座混凝土桥梁的疲劳剩余寿命进行预测计算。本项目是在理论层面对混凝土疲劳性能进行的基础研究，其成果能够对国内日趋严峻混凝土桥梁管养工作起到推动作用，具有重大的现实意义和经济价值。