深中通道泄洪区非通航孔桥主梁设计

Design of Main Girder of Non-navigable Bridges of Shenzhen-Zhongshan Link in Flood Diversion Zone

深中通道泄洪区非通航孔桥总长6.05 km,分布于伶仃洋大桥及中山大桥2座通航孔桥两侧。泄洪区非通航孔桥采用等跨连续梁布置,4~6跨一联。主梁设计过程中,首先进行110、120、130 m三种跨径方案比选,确定采用最经济的110 m跨径方案。然后针对结构形式,提出预应力混凝土梁、钢-混组合梁和钢箱梁3种方案,从力学性能、经济性和施工风险等方面综合考虑,最终推荐采用钢箱梁方案。钢箱梁采用外形简洁流畅的封闭式断面,有利于后期维养;考虑全线景观效果,主梁高度取4 m,高跨比为1/27.5;横隔板间距取2.5 m,采用实腹式横隔板和框架式横肋的组合式设计,使箱室内部通透性更好;钢箱梁采用Q420qD钢和Q345qD钢2种材料。钢箱梁施工采用适合海上长大桥梁的大节段预制+现场拼装的施工方案。

The non-navigable bridges in the flood diversion zones that create connections among the Lingdingyang Bridge,Zhongshan Bridge and approaches have a total length of 6.05 km.These bridges consist of multiple equal spans,with expansion joints installed every four to six spans.At the design stage,three span lengths of 110,120,and 130 m were compared,and the 110 m-long spans were proved the ideal choice in terms of economy.Three types of girders,including the prestressed concrete girder,the steel-concrete composite girder and the steel box girder,were compared from perspectives of mechanical properties,economy and construction hazards,and the streamlined steel box girders that would facilitate future maintenance were selected.Given the landscaping effect of the entire crossing,the depth of steel box girders was determined to be 4 m,leading to a girder depth to span length ratio of 1/27.5.The center-to-center spacing of the solid diaphragms is 2.5 m.Framed transverse stiffeners are utilized to provide open views inside the box girders.The steel box girders are made of Q420qD and Q345qD steel.To ease the construction,the steel box girders were first fabricated into large segments off site and delivered to the bridge site for assembly.