六沾铁路宣天特大桥主桥设计

六沾铁路宣天特大桥主桥为钢管混凝土拱加劲三跨连续梁桥,主跨为100 m。主梁为双纵梁的"П"形双向(局部三向)预应力混凝土结构,钢管混凝土加劲拱圈由2条相互平行的拱肋及横向联结系构成,拱肋为变高度钢管混凝土桁架,拱圈平联采用"ж"形空心钢管桁架,吊杆采用钢绞线体系。计算主梁应力、挠度、自振特性及钢管混凝土的钢管及混凝土应力;经试算,吊杆预张力、安全系数均满足要求。根据有限元分析结果,对拱-梁结合部进行设计改进:主梁上翼缘增加4束纵向短束;加强纵梁上翼缘普通钢筋布置;优化竖、横向预应力根数和布置。采取先梁后拱满堂膺架的施工方案。

Design of Main Bridge of Xuantian Bridge on Liupanshui-Zhanyi Railway

The main bridge of the Xuantian Bridge on Liupanshui-Zhanyi Railway is a threespan continuous girder bridge stiffened by the concrete-filled steel tubular(CFST)arches and with a main span 100 m.The main girder of the bridge is of a"Π"-shape two-way(locally threeway)prestressed concrete structure having double longitudinal girders and the stiffening CFST arch rings ate made up of the two parallel arch ribs and lateral bracing systems.The arch ribs are the CFST trusses with variable cross sections and are braced by the"ж"-shape hollow steel tube trusses.The hangers are the steel wire strand systems.The stress,deflection,nature vibration characteristics of the main girder and the stress of the steel tubes and concrete of the structure are calculated.Through the calculation,the pretensioning force and safety coefficient of the hangers are proved to satisfy the requirements.The design of the connections of the arches and girders is improved in accordance with the finite element analysis:in the upper flanges of the girders,four numbers of the short longitudinal strands are added,the arrangement of the ordinary reinforcement there is strengthened,the arrangement of the numbers of the vertical and transverse prestressing strands is also optimized and finally the bridge is to be constructed on stages by way of erecting the girders first and arches late.