基于神经网络的斜拉桥钢箱梁局部连接细节腐蚀疲劳可靠度研究（双语出版）

腐蚀与疲劳是影响斜拉桥钢箱梁服役可靠性的关键因素，为研究两者双重作用下斜拉桥钢箱梁服役期可靠度的衰退规律，开展了基于神经网络技术的斜拉桥钢箱梁局部连接细节腐蚀疲劳可靠度分析。首先，通过疲劳强度与钢材强度的关系以及腐蚀引起的钢材抗力衰变，得到了钢材腐蚀疲劳抗力时变模型。然后，通过基于均匀设计法的神经网络技术和非线性有限元方法进行斜拉桥钢箱梁腐蚀疲劳时变可靠度分析。采用均匀设计法得到影响结构可靠性的基本随机变量的设计样本点，基于ANSYS求解样本点处疲劳荷载作用下的钢箱梁应力幅，通过神经网络得到钢箱梁构件的应力幅函数显式表达式。在建立腐蚀疲劳抗力和疲劳荷载效应时变模型的基础上，构建了斜拉桥钢箱梁局部连接细节腐蚀疲劳时变可靠度的显式功能函数，基于FERUM程序采用JC法计算斜拉桥钢箱梁腐蚀疲劳时变可靠指标。最后以苏通大桥为例，采用所提方法对钢箱梁局部连接细节服役期的腐蚀疲劳时变可靠度进行了计算，并进行了参数敏感性分析。结果表明：桥面板和U肋腐蚀疲劳可靠指标均随时间增加而减小，但桥面板腐蚀疲劳可靠指标衰退越来越快，而U肋腐蚀疲劳可靠指标则衰退越来越慢，桥面板腐蚀疲劳寿命不足100年。研究结果为斜拉桥钢箱梁服役期的运营维护提供了指导。

Corrosion Fatigue Reliability of Steel Box Girder Connection Details of a Cable-stayed Bridge Based on a Neural Network（in English）

Corrosion and fatigue are the key factors that affect the service reliability of steel box girders of cable-stayed bridges. To study the attenuation characteristics of the service reliability of steel box girders of cable-stayed bridges under the dual effects of corrosion and fatigue, a corrosion fatigue reliability analysis of the local connection details of the steel box girders of cable-stayed bridges was conducted based on neural network technology. First, based on the relationship between fatigue strength and steel strength as well as the attenuation of steel resistance caused by corrosion, a time-varying model of the corrosion fatigue resistance of steel was obtained. Then, a time-varying reliability analysis of corrosion fatigue of the steel box girder of a cable-stayed bridge was conducted using both a uniform design method based on neural network technology as well as a non-linear finite element method. The uniform design method was used to obtain the design sample points of the basic random variables that affect structural reliability. Based on ANSYS, the stress amplitude of the steel box girder under the fatigue load at a sample point was solved, and the explicit expression of the stress amplitude function of a steel box girder member was obtained by the neural network. Based on the time-varying models of corrosion fatigue resistance and fatigue load effect, the explicit function of corrosion fatigue time-varying reliability of the local connection details of the steel box girder of a cable-stayed bridge was established. The time-varying reliability index of corrosion fatigue was calculated using the method recommended by the Joint Committee of Structural Safety (i.e., the JC method) through the FERUM program. Finally, with the Sutong Bridge used as an example, the time-varying reliability of corrosion fatigue of the local connection details of steel box girders during the service period was calculated and the sensitivity of parameters was analyzed. The analysis shows that the reliability index of the corrosion fatigue of the bridge deck and U-rib decreases over time. However, the reliability index of the corrosion fatigue of the bridge deck decreases at a faster rate than that of the U-rib. In addition, the corrosion fatigue life of the bridge deck is determined to be less than 100 years. The results can be a reference for operating and maintaining the steel box girders of cable-stayed bridges during service periods.