麦麦高铁超宽混凝土箱梁桥构造与施工

Structure of and construction method to super-wide concrete box girder bridge of mecca to medina high speed railway

沙特麦加-麦地那高速铁路K2+854处采用超宽预应力混凝土箱梁桥,桥梁为多跨连续梁结构,该超宽箱梁采用单箱六室截面,最宽处达到67.3 m。为了确保桥梁安全,对超宽箱梁自重作用下的应力分布分别采用梁单元和实体单元进行的分析,对超宽箱梁的剪力滞效应进行了分析,结果表明,正应力最大值和最小值相差15%左右,在设计时不可忽略。施工时采用新型满堂支架施工,满堂支架为门式支架,立杆直径为?准60×4.0。因为桥梁超宽,在施工过程中采用分层分段施工的方法,腹板混凝土的约束作用,易在强度还未充分发展的顶板混凝土中产生裂缝。因拉应力的存在,需合理配筋,限制裂缝的开展。因钢筋布置密集,混凝土浇筑时采用自密实混凝土,避免了振捣,保证了混凝土箱梁的施工质量。

A super wide 6-cell concrete box girder,with a width of 67.3 meters,is used at the location of K2+854 for Mecca to Medina High-speed Railway.The bridge is a 4-span continuous girder.To ensure the safety of the bridge,the stress distribution of the super wide 6 cell box girder under self-weight are analyzed using beam element and solid element in fea program.The result shows that a 15%difference exists between the maximum normal stress and the minimum normal stress.It is cannot be neglected in the design.A new portal type of scaffolding system is adopted to construct the bridge.Due to the super width of the girder,the concrete is casted by layers and by segments.the concrete of the top plate of box girder is apt to crack due to the transversal tensile stress due to the constraint of the contract by the webs cast earlier.Because the spaces of the steel bars are so small,it is difficult to vibrate the concrete using a vibrating bar,so the self compact concrete is used to ensure the quality of concrete of the girder.