Tuned Liquid Damper (TLD) utilizing the motion of shallow liquid for absorbing anddissipating the vibrational energy is studied with emphasis on liquid motion. Amathematical model based on the nonlinear shallow water wave theory is presented todescribe the liquid motion in a rectangular tank. Liquid damping is evaluated semi-analytically and is included in the formulation. Mechanical properties of: TLD are alsoexperimentally investigated using the shaking table. It is found that the liquid motion inTLD is strongly nonlinear and reveals a hardening-spring property even under smallexcitation, Good agreements between the simulation and the experimental results areshown when no breaking wave occurs. The model presented in this study is expected toserve as a tool for TLD design.

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.

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.

Donghai bridge is a linkage connecting Luchao Port in Shanghai and Yangshan Island deep Water Port. The linkage is about 32km long and consists of 2 cable stayed bridges and a large number of spans of eontinuous and simply supported bridges. It crosses East China Sea and lies on soft clay so the durability gainst ocean environment and the un-uniform settlement of foundations are concerned. The bridges are under construction and are planed to open to traffics around the end of 2005. A structural health monitoring system designed and is being installed to the bridge. This paper reported the conceptual design and the key issues thpse have been studed on the structural health momtonng system of the bridge.