季节性冻融作用下预应力混凝土结构疲劳性能退化与寿命预测

Bridges in cold regions suffer from the effects of seasonal freeze-thaw; there is an obvious interaction between freeze-thaw cycles and repeated loadings. Under the interaction of freeze-thaw cycles and repeated loadings the concrete damage and prestress losses of prestressed concrete bridge structures will aggravated, resulting in structure fatigue behavior degradation, which can seriously jeopardize the safe use of bridges. Prestressed concrete bridge structures in cold regions were chosen as the research object, and accurately assess its fatigue life as the research goals. A systematic thorough study will be conducted on the concrete damage evolution, prestress losses, fatigue behavior degradation and fatigue life prediction of prestressed concrete structures under interaction. Experimental investigation, theoretical analysis, numerical simulation and engineering validation are combined as the research methods. The damage evolution mechanisms and damage evolution rules of concrete under interaction will be investigated and analyzed, and the uniaxial compressive fatigue constitutive law model of concrete under interaction will be established. The prestress losses rules in prestressed concrete components subjected to interaction will be studied and the prestress losses model will be proposed. The fatigue behavior degradation mechanism of prestressed concrete components suffered from interaction will be revealed, the fatigue life prediction model for prestressed concrete components subjected to the effects of seasonal freeze-thaw will be proposed. The research results of this project can provide a reliable basis for assessment the service performance of prestressed concrete structures in cold regions.

寒冷地区桥梁工程会遭受季节性冻融作用，冻融循环与重复荷载存在明显的交互作用，交互作用造成预应力混凝土桥梁结构材料损伤加剧，引起预应力损失增大，导致结构疲劳性能退化，严重威胁桥梁的安全运营。本项目以寒冷地区预应力混凝土桥梁结构为研究对象，以准确评估季节性冻融作用下预应力混凝土结构的疲劳寿命为目标，围绕冻融循环与重复荷载交互作用下预应力混凝土结构材料损伤演化、预应力损失、构件疲劳性能退化与寿命预测开展系统研究。采用试验研究、理论分析、数值模拟和工程验证相结合的方法，考虑冻融循环与重复荷载交互作用，研究混凝土在交互作用下的损伤演化机理与演化规律，建立混凝土单轴受压疲劳本构模型；研究交互作用下预应力混凝土构件预应力损失规律，提出预应力损失计算模型；揭示交互作用下预应力混凝土构件疲劳性能退化机理，建立构件疲劳寿命预测模型。项目成果可为寒冷地区预应力混凝土结构服役性能评估提供可靠的理论依据和技术支撑。

寒冷地区桥梁工程会遭受季节性冻融作用，冻融循环与重复荷载存在明显的交互作用，交互作用造成预应力混凝土桥梁结构材料损伤加剧，引起预应力损失增大，严重威胁桥梁的安全运营。本项目以寒冷地区预应力混凝土桥梁结构为研究对象，以准确评估季节性冻融作用下预应力混凝土结构的服役性能为目标。采用试验研究、理论分析和数值模拟相结合的方法，系统研究了冻融循环作用下预应力混凝土材料损伤演化、钢筋锈蚀行为和预应力损失行为。.开展了冻融损伤钢筋混凝土试件的锈胀开裂试验，进行了立方体试块、棱柱体混凝土试件的快速冻融试验，并对经历不同冻融循环次数后的钢筋混凝土试件进行外加电流加速锈蚀试验。DIC（Digital Image Correlation）监测结果表明混凝土表面开裂点随机分布，试件表面相对变形在300με左右时出现陡增现象，混凝土初始开裂；试件钢筋临界锈蚀率随保护厚度与钢筋直径比值（c/d）的增大整体呈上升趋势，但随冻融循环次数增加而减小；采用双层厚壁圆筒模型，建立了以冻融循环次数和混凝土抗压强度为主要参数的冻融环境混凝土锈胀开裂条件计算模型，且计算结果与试验结果吻合较好。.开展了预应力混凝土构件在冻融循环作用下的预应力损失试验，分析了材料损伤、损伤前有效预应力、孔道灌浆等对预应力损失的影响机理与影响规律，建立了冻融循环作用下预应力混凝土构件预应力损失计算模型。.项目成果在《Journal of Structural Engineering ASCE》、《Engineering Structures》、《Construction and Building Materials》、《建筑结构学报》、《建筑材料学报》等权威期刊发表发表论文11篇，其中SCI论文5篇、EI论文3篇，1篇论文入选ESI高被引论文；申获国家专利5项，其中发明专利3项；获省部级、厅局级科技进步一等奖2项；参与编制协会、地方标准2部；参加国内国际学术会议5次；培养硕士生5人。