三门峡黄河公铁两用大桥主桥为(84+9×108+84)m 的11跨连续钢桁结合梁桥,采用双层桥面布置,下层桥面通行4线铁路(双线蒙西通道+双线运三铁路),上层桥面通行双向6车道高速公路.该桥主梁采用密横梁体系钢桁结合梁,横向布置3片主桁,主桁采用三角形桁式.下层铁路桥面采用密横梁体系的正交异性整体钢桥面板,钢轨处设置倒 T形小纵梁;上层公路桥面采用C60的钢筋混凝土结合板,通过湿接缝和剪力钉与钢主桁上弦杆及横梁结合为整体;主桁横向未设置联结系,仅在两端的公路横梁底设置板式桥门架.采取选择合理的混凝土板结合及顶落梁工序、选择合适的预制板存放龄期、湿接缝处理和加强预制板配筋等措施改善结合梁负弯矩区混凝土板受拉开裂的问题.主桥钢桁梁采用拖拉式顶推的方法施工.%The main bridge of Sanmenxia Huanghe River Rail-cum-Road Bridge is a 1 1-span continuous steel truss composite girder bridge with span arrangement(84+9×108+84)m.The bridge is designed as a double-deck bridge.The lower deck of the bridge is to carry the 4-track rail-ways(2 tracks for Inner Mongolia Westbound Railway+2 tracks for Yuncheng-Sanmenxia Rail-way)while the upper deck to carry the dual 3-lane expressways.The main girder of the bridge is the steel truss girder provided with the dense cross beam system.In the transverse direction of the main girder,3 main trusses of the triangle shape trusses are arranged.The lower railway deck is the one having the integral orthotropic steel deck plates supported on the dense cross beam system and at the locations where the steel rails are to be laid,the inverted T-shape stringers are ar-ranged.The upper highway deck is the one having the C60 reinforced concrete deck slabs that are connected into an integrity with the upper chords and cross beams of the steel main trusses via the wet joints and shear studs.In the transverse direction of the main trusses,the bracing systems are not arranged while only at the bottom of the highway cross beams at the both ends,the plate por-tal frames are arranged.A number of the measures of selecting the proper working procedures for the concrete slab connecting and the main truss jacking-up and-down and of selecting the proper storage age of the precast concrete slabs,properly handling the wet joints and enhancing the rein-forcement in the concrete slabs was taken so as to improve the tensile cracking problem of the con-crete slabs in the sagging moment areas of the composite girder.The steel trusses of the main bridge are to be erected by the hauling and pushing construction method.
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