Key Construction Control Techniques for the Steel Truss Girder Bridge Crossing Heng-Gang-Sha of the Shanghai-Suzhou-Nantong Yangtze Highway and Railway Bridge

The bridge crossing Heng-Gang-Sha of the Shanghai-Suzhou-Nantong Yangtze River Highway and Railway Bridge is a simply-supported steel truss girder bridge with 21 spans of 112 m（between Piers No.5 and No.26）. The superstructure of the bridge is a structure of three-main-truss. The bridge was constructed by the method of “from continuous to simply-supported with free cantilever erection”. To ensure the safety of cantilever assembly construction， and the internal forces in the installation of highway bridge decks and railway through girders meet the design requirements，a finite element model of the completed bridge was developed in MIDAS for the whole construction process analysis.The construction control was conducted by using the allowable stress method. During the single cantilever erection， the full scaffolding was installed between Piers No.10 and No.11， and then the bridge deck crane was used to assemble the cantilever of Piers No.5 and No.19， respectively， the 1100 t·m tower crane was used to install the bracket support near Pier No.22. After installing the steel truss between two segments on both the north and south sides of the top of Pier No.22 and making temporary connections at the pier cap， synchronized double-cantilever erection proceeded toward Piers No.26（south） and No.19（north）. During the construction， the girder truss crane for bridge decks was set between Piers No.10 and No.11. After the conversion of the hanging steel truss girder from continuous to simply-supported system， the lifting and installation of the highway bridge decks and railway through girders began simultaneously， along with the construction of wet joints. Both the maximum axial pressure and maximum compressive stress of the steel truss beam met the design requirements； the implementation of lateral restraint devices ensured compliance with crosswind stability requirements； by elevating the pier top to a specified height，the height of the construction modes of "1 + 1"， "2 + 1"， and “3+1” met the construction requirements， while the peak stress under the maximum cantilever met the design and specification requirements. After the installation of decks and through girders， the maximum mid-span displacement of the steel truss girder was approximately 50 mm， meeting the specification and design requirements.By adopting a series of construction control measures such as pier-top limit control， pier scheme control， temporary connection parts of pier-top control， and emergency control of extreme wind conditions， the safe erection of the large steel truss girders across the Shanghai-Suzhou-Nantong Yangtze River Highway and Railway Bridge was effectively guaranteed.