正交异性钢桥面板疲劳寿命设计优化研究

Research on Fatigue Life Design Optimization of Orthotropic Steel Deck

采用有限元计算方法,对某大桥钢桥面铺装在采用钢-UHPC超轻型组合梁优化前后的钢箱梁节段正交异性钢桥面板的主要连接接头进行了分析,研究了在轮轴荷载作用下主要疲劳裂纹的控制应力的分布特征及应力影响面,建立了较全面的荷载作用与应力效应的对应关系,并由此推算出实桥在设计疲劳荷载作用下的应力历程及相应的应力谱。针对设计疲劳寿命周期内的正交异性钢桥面板的各构造细节,根据Miner疲劳损伤累积理论计算出相应的疲劳累积损伤,并对其疲劳寿命进行评估。采用普通钢桥面铺装时,靠近顶板与U肋、U肋与横隔板连接处的主要疲劳裂纹,其疲劳累积损伤度在设计使用寿命周期内均大于1,存在较高的疲劳开裂风险。经钢-UHPC超轻量组合桥面板设计优化后,顶板与U肋连接处抗疲劳性能改善效果显著,在大桥设计寿命周期内可满足抗疲劳设计的使用要求;但设计优化对横隔板-U肋-顶板连接处的抗疲劳性能影响有限,在设计使用寿命周期内,疲劳裂纹C.5、C.6、C.6.1、C.7仍存在较高的开裂风险,需引起重视。

By using the finite element method,the main joints of the orthotropic steel deck of the steel box girder segment before and after the optimization of the steel UHPC super light composite beam used for the steel deck pavement of a bridge are analyzed.The distribution characteristics of the control stress and the stress influence surface of the main fatigue cracks under the wheel axle load are studied,and a more comprehensive relationship between the load effect and the stress effect is established;the stress history and the corresponding stress spectrum of the real bridge under the design fatigue load are further calculated.According to the structural details of orthotropic steel bridge deck in the design fatigue life cycle,the corresponding fatigue cumulative damage is calculated according to Miner's fatigue damage accumulation theory,and its fatigue life is evaluated.The main conclusions are as follows:when ordinary steel deck pavement is used,the fatigue cumulative damage degrees of the main fatigue cracks near the joints of top plate and U-rib,U-rib and diaphragm are greater than 1in the design service life cycle,and there is a high risk of fatigue cracking.After the design optimization of steel UHPC ultra lightweight composite deck,the fatigue resistance of the connection between the top plate and the U-rib is significantly improved,which can meet the service requirements of the fatigue resistance design within the design life cycle of the bridge.However,the design optimization has limited impact on the fatigue resistance of the diaphragm-U rib-top plate connection.During the design service life cycle,there is still a high risk of fatigue cracks in C.5,C.6,C.6.1and C.7,which should be paid close attention to.