【作者】 阮毅；

【导师】 宗周红；

【作者基本信息】 福州大学 ， 结构工程， 2004， 硕士

【摘要】 既有桥梁是我国经济现代化的基础和宝贵财富，由于自然环境作用和日益增长的交通量及载重量，大量既有桥梁功能退化，加固维修的任务十分艰巨。对既有桥梁承载力做出科学评判，保障桥梁结构的安全使用性能，科学合理地进行决策及加固维修，保证交通大动脉的畅通具有重大的社会意义和经济价值。本文基于如下桥梁动力评估步骤，对已运营四年多的福州市三县洲闽江大桥的承载力进行评估：1. 建立结构的初始有限元模型，进行自由振动分析得到桥梁大致的动力学特性。2. 进行实桥在环境激励下的动载试验，测量该桥的竖向、扭转、横向以及纵向的动力特性，所有拉索的索力及桥面线型。3. 用频域的峰值法（PP）、时域的随机子空间系统识别方法（SSI）对桥梁动力学参数进行识别，得到桥梁结构实际的动力特性。根据实测结果进行有限元模型的参数修正，得到反映桥梁现时真实工作状态的较精确的有限元模型。4. 以修正后的有限元模型为基础，采用数值加载的方法，进行“设计汽车荷载”下桥梁的承载力计算和分析，从而实现既有桥梁结构承载力的确定性评估。5. 改变有限元模型中影响桥梁承载力的主要参数（拉索面积、混凝土弹性模量、伸缩缝刚度及桥面活载）来模拟损伤，采用承载能力系数法对其承载力进行预测评估。 得到的主要结论如下： （1）三县洲大桥动力特性的实测结果与有限元计算结果能够吻合，大桥的整体动力特性良好。（2）大跨径斜拉桥的动力特性受跨度、主塔及拉索布置方式、上部主梁类型、边界约束方式等的影响。对三县洲大桥而言：其横向基频（0.942Hz）要大于竖向基频（0.440Hz）。本桥由于塔梁墩固结，其纵桥向基频较高（2.452Hz）。（3）该桥在运营四年后，索力、挠度、应力与主塔偏位都在设计允许的范围内，大桥依然具备通行设计汽车荷载的能力。（4）对该桥承载力的预测分析表明：在所分析的可能损伤状态下，拉索具有足够的安全系数，损伤对控制截面的承载能力系数影响较大。更多还原

【Abstract】 Existing bridges are the foundation and precious treasure of the economy modernization of our country. Due to the effect of environment and the increasing traffic and vehicle load, the functions of great amount of existing bridges degenerated, so the reinforcement and maintenance of the existing bridges are very hard. It has great social significance and economic values to evaluate the load-carrying capacity of existing bridges, and helps to ensure the security of existing bridge structures, decide the strategy of repairing and maintenance scientifically, and assure the traffic artery smoothly. In this thesis, the evaluation of the load-carrying capacity of Sanxianzhou Bridge, over the Minjiang River, Fuzhou, Fujian Province, was conducted, based on the following steps: 1. The initial FE model was established based on the design drawings, and approximate dynamic characteristics of the bridge were obtained through the analysis of free vibration. 2. The field ambient vibration tests induced by wind and normal traffic were carried to determine the real dynamic characteristics, including vertical, torsional, transversal and longitudinal frequencies and modal shapes, each cable tension force, as well as the figure of the bridge deck. 3. The out-put only data modal parameter identification was conducted by using the peak picking(PP) method in frequency-domain and stochastic subspace identification(SSI) method in time-domain, the realistic dynamic characteristics of the bridge were obtained. After that, the FE model was calibrated in terms of ambient vibration test results, and more precise FE model was obtained, which could represent the current service condition of the bridge truly. 4. Based on the calibrated model, the numerical testing on the bridge under the design vehicle loading was carried out and the load-carrying capacity of the bridge in service was analyzed. So the determinate evaluation of the bridge can be performed. 5. The precise FE model was used to predict the factors of load-carrying capacity of the controlled sections of the box-girder, by selecting some important factors which can affect the load-carrying capacity, such as the area of cables, stiffness of expanding joints, elastic modulus of concrete, and the amount of living load, to simulate the several possible damages of the bridge in service in the future.<WP=4> Several conclusions are listed as follows: 1. The dynamic characteristics of Sanxianzhou bridge under field-testing agreed well with that of the FE calculation. This indicated that the whole dynamic characteristics of the bridge is well. 2. The dynamic characteristics of long-span cable-stayed bridge were affected by span, main tower, cable arrangement, main girder type, constraining manners of boundary, etc. For this bridge, the transversal fundamental frequency(0.942Hz) is higher than the vertical fundamental frequency(0.440Hz), and longitudinal fundamental frequency(2.452Hz) is quite high because the main girder, the main tower and the pier of the bridge are fixed together. 3. After running four years, the cable forces, the main girder’s deflection and stress, as well as the main tower’s displacement of the bridge were in the range of design permission. The bridge still has the capacity to bear design traffic load. 4. The prediction analysis showed that the cables have enough safety factor, but the factors of load-carrying capacity of controlled cross sections of main girder may vary a great deal under several possible damage conditions.更多还原