大跨度提篮式人行拱桥的振动病害分析与加固-桥梁与隧道工程专业论文.docxVIP

Abstract Over the last years, with increasing strength of new structural materials and aesthetic requirements for greater slenderness, the trend in footbridge design has been towards greater spans and increased flexibility and lightness. As a consequence, stiffness and mass have decreased, which has lead to smaller natural frequencies and more sensitivity to dynamic loads. Many footbridges have natural frequencies that coincide with the dominant frequencies of the pedestrian-induced load and therefore they have a potential to suffer excessive vibrations under dynamic loads induced by pedestrians. In the past few years the vibration serviceability problem of footbridges attracted great public attention. To analysis the vibration of footbridges by human-induced dynamic loads, this thesis introduced models for dynamic pedestrian loads, the theoretics of forced resonance vibration and the method to assess vibration serviceability. For the lacking of researches on human-induced vibration of footbridges currently, this thesis proposed a referenced method of dynamic design of footbridges by comparing and analysising current design criteria and codes for footbridges in other countries. There are two methods of dynamic design of footbridges, tuning the natural frequencies of the structure or analysising dynamic response of structures to human-induced loads. And the latter is more reasonable. when the low natural frequencies of a footbridge are in the range of 1.4~2.4Hz for the vertical direction and in the range of 0.7~1.2Hz for the horizontal direction, it is required to analysis the dynamic response to human-induced loads and assess vibration serviceability. This thesis took the Rainbow bridge in BaiShan city of JiLin province for an example to analysis the mechanical characteristics of X arch bridges. After inspecting the situation of the Rainbow bridge and assessing it, the reasons for excessive vibration under human-induced loads were found. Also, assessing vibration