多源荷载下悬索桥钢桥面板的易损性评估及参数优化方法研究

It is a serious problem that orthotropic steel deck being widely used in long-span suspension bridge is vulnerable to fatigue impact, and steel deck design existing for fatigue is inadequate. Considering the coupling effect of multi-excitation and timing unsteady characteristics of fatigue state transfer of steel deck system, the key scientific issues of steel deck fatigue damage mechanisms and design for resistance to damage will are systematically studied combined with a in-site bridge health monitoring and large scale model test, in which the Xihoumen Bridge is as engineering background. The main contents are as following: The coupling characteristics of multi-excitation along the time history based on multi-scale theory will is analyzed, and which will is expanded to life cycle of the structure. Considering linear and nonlinear factors, the correlation of typical fatigue damage pattern and multi-excitation in time-frequency domain will is identified, and the damage criteria based on analysis of the disaster consequences will is established. The vulnerability assessment model based on multi-excitation time-dependent effects will is deduced. The parameters optimization method will is researched and developed to effectively reduce the vulnerability of steel deck system. The relationship of the critical mechanical parameters evolution and the transfer rate of the fatigue state in steel deck system will is proved to achieve comprehensive assessment of the sustained service ability of steel deck. Thereby, the new vulnerability assessment methodology and design technique for resistance to damage in suspension bridge with orthotropic steel deck will are developed and obtained, which will provide important theoretical and technical support to more large span suspension bridge with steel box girder.

针对大跨径悬索桥中广泛应用的钢箱梁桥面板易受疲劳损伤的突出问题和现有钢桥面板抗疲劳设计的不足，本项目综合考虑多源荷载的耦合作用和钢桥面板系统疲劳状态转移的时序非稳态特征，以西堠门大桥为工程背景，结合实桥健康监测和大比例模型试验，对钢桥面板疲劳损伤机理和抗损设计中的关键科学问题进行系统地研究。主要开展：基于多尺度理论分析多源荷载沿时间历程的耦合特征，实现向结构全寿命周期拓展；考虑线性和非线性因素识别典型疲劳损伤模式与多源荷载的时—频相关性，建立基于致灾后果分析的损伤准则；推导建立基于多源荷载时序作用的易损性评估数学模型；研发能够有效降低钢桥面板系统易损性的设计参数优化方法；探明钢桥面板中关键力学参数演变历程与疲劳状态转移速率的关系，实现综合评估钢桥面板的持续服役能力。从而研发出悬索桥钢桥面板易损性评估和抗损设计的新理论及新方法，为钢箱梁悬索桥向特大和超大跨径发展提供重要的理论和技术支撑。

针对大跨悬索桥钢箱梁疲劳开裂难题，本项目运用理论分析、数值模拟及长期现场监测数据对正交异性板U肋的剩余强度退化规律进行研究，以特大跨径钢箱梁悬索桥-西堠门大桥为工程背景展开研究。首先分析了西堠门大桥钢箱梁长期应变监测数据的时频特征，应用小波分析分离出了环境温度变化所引起的桥面板结构应力波动，再对小波变换系数在不同尺度上选择合适的阈值来消除由环境随机激励和测量噪声引起的低幅值应力变异；采用雨流计数法对车辆荷载作用下的应变监测数据进行了统计分析，得到了疲劳应力范围并设定了6个疲劳应力区间；然后由U肋对接部位的典型S-N曲线计算得到其强度从初始状态至最终状态的转移概率，并根据Palmgren-Miner线性疲劳累积损伤理论构造出连接部位易损点区域强度演变的状态转移概率矩阵；最后利用初始状态的概率分布向量和状态转移概率矩阵，得出了大桥运营阶段不同时刻对应的剩余强度值，给出了U肋连接部位的强度退化轨迹。所建立的疲劳状态分析模型可以考虑构件强度退化过程中各状态的相关性，能够根据车流量变化来预测正交异性板U肋疲劳状态随桥梁服役时间的变化规律，具有重要的理论价值及现实意义。