Fatigue Durability of Concrete Bridge Decks

密歇根大学的Victor Li研究了混凝土桥面的疲劳耐久性。最近的研究表明，疲劳开裂可能是混凝土桥墩严重破坏的前兆。疲劳损伤的基本原理和相应的桥面补救措施目前还知之甚少。本研究的重点是对混凝土桥面疲劳耐久性的基本认识和使用纤维增强材料提高疲劳耐久性。纤维增强混凝土(FRC)的抗疲劳性能在实验室得到了广泛的研究，因此纤维增强特别受到重视。采用基于统计/细观力学的理论模型，分析了疲劳荷载作用下的裂纹扩展机理，以及循环荷载作用下的聚集和纤维桥联(跨越混凝土裂缝)响应。本研究的四个重要结果是：1)抗疲劳损伤的桥面板设计程序；2)对FRC疲劳破坏机理的基本理解；3)基于细观力学的抗疲劳FRC复合材料设计模型；以及4)FRC桥面板的评估/修复程序。这项研究导致了基于机构的结构性能设计，迫使材料与结构工程紧密联系。所采用的方法是实验和理论工作相结合。重点介绍了桥面性能的现场数据和疲劳试件的试验数据。这项研究的性质需要桥梁工程和复合材料工程的综合知识。

Victor Li, University of MichiganThe investigation addresses the fatigue durability of concrete bridge decks. Recent research suggests that the fatigue cracking can be a precursor to severe failure of concrete bridge docks. The fundmentals of fatigue damage and corresponding remedial action on bridge decks are currently poorly understood. This investigation focuses on basic understanding of fatigue durability of concrete bridge decks and on fatigue durability enhancement by the use of fiber reinforcement. fiber reinforcement is especially focused on because of the extensive documentation of fatigue resistance enhancement of fiber reinforced concrete (FRC) in laboratory. The mechanism of crack growth under fatigue loading, and aggregated and fiber bridging (across a concrete crack) response subjected to cyclic loading, are analyzed with a statistical/micromechanics based theoretical model. In addition, the degradation of the fiber/cement and aggregate/cement interface are expilicitly accounted for based on experimental observations.Four important consequences of this research are:1) Bridge deck slab design procedure against fatigue damage; 2) Fundamental understanding of the mechanisms governing fatigue failure of FRC; 3) Micromechanics based model for design of fatigue resistance FRC composites; and 4) Evaluation/repair procedure of brige decks using FRC. This research leads to mechanism based structural performance design forcing a tight connection between materials and structural engineering. The approach adopted is combination of experimental and theoretical work. Field data of bridge deck performance and laboratory data of fatigue specimens are emphasized. The nature of this reseach requires combined knowledge of bridge engineering as well as composite materials engineering.