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城市轨道桥梁作为我国近年来大力发展的新型桥梁结构,其结构形式与受力特点不同于传统的铁路桥梁、公路桥梁和城市桥梁,2014年以前并没有专门与其对应的抗震设计规范。本文探讨了现行各桥梁抗震设计规范的特点及适用范围,并比较了各规范所给出的设计理念、计算方法及设计参数,据此,从现有规范中总结出一套行之有效的城市轨道桥梁延性抗震设计方法并应用于实例城市轨道桥梁。本文分析表明,延性结构通过塑性铰区域的变形,能够有效地吸收和耗散地震能量。同时,这种变形降低了结构的刚度,致使结构在地震作用下的反应减小,也就是使地震对结构的作用力减小,实现以变形能力来抵抗罕遇地震作用。反之,如果结构的延性不好,则必须有足够大的承载力抵抗地震,这样会耗用更多材料。因此,对于地震发生概率极少的抗震结构,采用延性结构是一种经济的设计对策。本文方法仅限于常规墩柱,高宽比小于2.5或大于10的墩柱,不在本次研究范围。
As a new type of bridge structure developed rapidly in recent years in our country, urban rail bridge is different from the traditional railway bridges, highway bridges and urban bridges in structural form and force characteristics. Before 2014, there was no specific seismic design code. This paper discusses the characteristics and applicable scope of the current seismic design codes of bridges and compares the design concepts, calculation methods and design parameters given by each specification. Based on this, a set of effective cities Ductile seismic design of track bridges and applied to example urban track bridges. The analysis of this paper shows that the ductile structure can effectively absorb and dissipate the seismic energy through the deformation of the plastic hinge region. At the same time, this deformation reduces the stiffness of the structure, resulting in a decrease in the response of the structure under the action of the earthquake, that is, the force acting on the structure by the earthquake is reduced, and the deformability is able to resist the rare earthquakes. Conversely, if the ductility of the structure is not good enough, there must be sufficient bearing capacity to resist the earthquake, which will consume more material. Therefore, the use of ductile structure is an economical design method for earthquake-resistant structure with very few earthquakes. This method is limited to conventional piers, pier with aspect ratio of less than 2.5 or more than 10, which is beyond the scope of this study.