对拉索-三单元Maxwell阻尼器系统的自由振动，运用复模态方法分析得到系统最优模态阻尼比和阻尼器最优阻尼系数的近似解析解，采用三单元Maxwell阻尼器模型模拟粘滞阻尼器、阻尼器内刚度和支架，得到拉索-三单元Maxwell阻尼器系统的运动方程，通过复模态分析得到以超越方程形式表达的系统自由振动阻尼特性的解析形式。对于阻尼器安装位置接近索端的情况，给出了有理函数形式的近似解析式。采用迭代法对解析形式的复特征频率方程进行了数值分析，结果表明近似解析式具有良好的精度。研究表明，阻尼器内刚度和支架柔度的耦合作用将显著削弱阻尼器的减振效果；阻尼器的最优阻尼系数随阻尼器内刚度的增大而增大，但随支架柔度的增大而减小。

Mechanical dampers are often installed near to anchorages of stay cables for mitigating vibrations due to wind or wind/rain. However, the optimal damping estimated by a linear theory is hard to be obtained and an efficiency factor between the designed damping and the practical one has to be considered for design. In this study, experiments of cable-damper system were conducted by using a 215 meters long full-scale stay cable. 7 types of mechanical dampers, including oil damper, viscous damper and MR damper, were adopted. The experimental results show that an inner type damper provided an additional damping (log decrement) 0.013, other outer type dampers provided additional damping larger than 0.030. Based on the experimental results, the authors suggest that the efficiency factor should be 0.3 for an inner type damper, and 0.5 for an outer type damper. The nonlinear design theory was also preliminarily studied.

The span of cable-stayed bridges has increased to more than 1000 meters, such as Sutong Bridge located in Jiangsu of China and Stonecuter Bridge in Hong Kong, both are under contruction. The longest stay cable for such large span bridges reaches to about 600 meters. Long stay cables are very senstive to circumstance excitation, such as wind, wind-rain or traffic loads, due to their low inherent damping. Wing-induced or wind-rain-induced vibrations are an important issue expecially. As countermeasures of cable vibration mitigation, mechanical damper, cross-ties or aerodynamic means are often adoped. A mechanical damper is usually installed near the anchorage of a stay cable in transversal direction to increase the modal damping of the cable. Cable cross-ties connect the stay cables together to increase the stiffness and the damping of the cable system. Besides of the effectiveness of mitigating wind-induced vibration, the cross-ties can increase the natural frequency of the cable system so the internal resonance and parameter vibrations can be avoided. An aerodynamic means modifies the surface condition of stay cable and is effective especially for suppressing the wind-rain-induced vibrations. This paper focuses on the vibration mitigation countermeasures using mechanical damper and cross-ties. A full scale experiment of cable with various types of mechanical dampers was conducted. The effects of damper nonlinearity and stiffness were investigated. The comparison of analytical damping calculated from nonlinear theory and equivalent linear theory to that obtained from experiment was conducted. Parametric studies on cross-ties were carried out by numerical simulations.

This paper presents the most recent development in the research, implementation andissues for future studies of structural health monitoring systems for large span bridges in China. Aftera brief review on the large span bridge projects in recent years and main deterioration and defectsproblems of existing bridges, this paper puts the focus on the review of the following three aspects: theimplementation of structural health monitoring system for large span bridges, the advanced sensing,transmission, and system integration technologies, and the novel signal processing and conditionassessment techniques. Through the review, a discussion on the issues for the future implementationof structural health monitoring system is offered.

对人行桥人行激励竖向振动的国内外现有规范和标准进行了比较研究，并探讨了针对侧向人行激振的振动使用性设计方法。建议人行桥梁设计时应首先采用频率调整法，使结构自振频率尽量不落在敏感频率范围内，不能达副频率要求时，再进一步采用动力响应法分析。在参考国外规范的基础上，建议确定竖向和侧向人行激振荷载的计算公式，该公式考虑了高阶分量的影响，还对人行桥振动舒适度标准进行了比较，认为参用英国规范的标准较为合理。