一种新型跨线桥——连续钢箱梁设计

Design of Continuous Steel Box Beam of New Flyover Bridge

研究目的:跨越既有线桥梁的结构选型不但要考虑施工方法、施工进度,更重要的是要考虑下方既有铁路的运营安全。合理的结构选型不但能保证工程顺利完工,同时对下方的线路运营干扰达到最小。连续钢箱梁是一种新型的铁路桥梁结构形式,其封闭的结构外形能有效规避施工时杂物坠落,同时具有灵活的配孔条件,且无需临时墩施工,适用于施工空间受限的桥梁,是跨越既有线最优的选择。基于此,本文以大西线联络左线特大桥为工程背景,对钢箱梁的计算方法、温度取值、桥面混凝土断缝方式以及支座处应力集中问题等进行探索。研究结论:(1)按全桥建模和简化计算对全桥进行了计算,并作出了对比;(2)对于不均匀升温,现行规范仅对混凝土箱梁及带混凝土桥面板的钢结构作出了规定,而对钢箱梁结构尚未作出规定,本次设计中参照英国规范BS 5400进行取值;(3)对桥面板混凝土采取部分断开的断缝形式;(4)桥梁支撑处依托底板纵横向加劲肋,在底板支承处局部灌填微膨胀混凝土,钢板与混凝土之间采用密布剪力钉连接,可以充分利用混凝土良好的受压性能及钢材优越的抗拉性能,有效提高该处的支承刚度,显著优化该处的应力分布;(5)该研究成果可为今后同类型桥梁的设计提供参考和借鉴。

Research purposes： The structure selection of bridge across the existing lines should not only consider the construction method and construction schedule, but also consider the operation safety of the existing railway. Reasonable structure selection can not only ensure the successful completion of the project, but also minimize the interference to the operation of the lower line. Continuous steel box girder is a new railway bridge structure, the structure shape closed can effectively avoid the construction debris fall, also has a flexible matching condition, without temporary pier construction, which is suitable for bridge construction with limited space, is the best choice across existing lines. In this paper, taking the Extra- long Bridge of Datong- Xi＇an dedicated passenger tie -line as the engineering background, the calculation method of steel box girder, the temperature value, the fracture mode of bridge deck concrete and the stress concentration at the abutment are explored. Research conclusions： （1） The whole bridge is calculated by full bridge model and simplified calculation, and the comparison is made. （2） For the uneven heating, the current standard only prescribes on the steel structure and concrete box girder with concrete bridge deck, and didnt make provisions on the steel box girder structure, the designrefers to the British standard BS 5400 value. （3） For the bridge deck concrete, break -joint form of partial disconnecting is adopted. （4.） The bridge support relies on vertical stiffener plate based on irrigation, partial filling of micro expansive concrete in the floor support, with shear stud connections between steel plate and concrete, which can make full use of the good compressive property of concrete and advantageous tensile property of steel, can effectively improve the bearing stiffness, significantly optimize the stress distribution. （5）The research results can provide reference for the design of the similar bridges in the future.