通过对原有钢筋混凝土结构扩展散体单元模型予以改进，提出了质点一桁架模型。将钢筋混凝土离散成单个质点，质点之间用桁架杆（非线性弹簧）联结，局部的破坏通过弹簧联结的断裂进行模拟，由此可计算结构从局部破坏到整体倒塌的全过程。借助面向对象的程序（00P）语言visual C+编制了分析软件，并计算了一个地震作用下独柱式桥墩倒塌的实例。计算结果表明，运用散体单元法分析桥梁倒塌，可直观地定性把握结构损伤发展直至倒塌破坏的全过程，对于结构倒塌破坏的机理研究具有重要意义。

In this paper, a method based on the artificial neural network technology, which is used to iden-tify two moving vehicles load on a simply supported bridge, is discussed. A multi-step identification procedure, which can be used effectively to identify multiple vehicle parameters such as loadlocation, load magnitude, andmoving speed, is proposed. The sensitivity of various input variables to the output and the effect of variation ofsample number to the identification result are investigated. The example data for training and verification aregenerated by theoretical simulation. The identification simulation shows that the proposed ANN method andprocedure can identify the moving vehicle load problem with acceptable accuracies. The ANN can also identifythe vehicle loads withclosed spacing and high moving speed, for which a conventional TDM or FTDM does notgive good identification results.

The pushover analysis is becoming popular as a simple method for seismic performance evaluation ofstructures. This paper presented a pushover analysis model, which can take account of soil-pile-structureinteraction. As load pattern for pushover analysis, monotonic increasing inertial forces was applied to asuperstructure and shear deformation was applied to soil respectively. A bridge pier-pile-soil system wasanalyzed by using the presented model, and the results were compared with those of nonlinear dynamictime history analysis, it was showed that the improved pushover method and its parameters determinationwere proper for providing a reasonable estimate of the structural maximum response. In order to embodythe nonlinearity of soil, nonlinear soil springs contacting piles and soil should be adopted in the modelinstead of equivalent linear ones. A static experiment of multi-pile foundation in a shear deformation soilbox was carried out to study the effect of soil movement on a multi-pile foundation, the relationship ofsoil-pile interaction force and relative deformation, and the determination method of the nonlinearinteraction spring.

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。

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.