The north block of the Belt and Road Cultural Exchange Center series public construction project is a 400 m long asymmetric twin tower connected structure,among which the 150 m aerial bridge is the single steel connected bridge with the largest span in China.The steel bridge weighs about 42 000 kN and is welded to the towers at both ends.The main body of the bridge is composed of sheet trusses,arc-shaped triangular trusses and the horizontal beam supports between them.At one end of the bridge is provided with a 36 m long and 4 500 kN weightunder theaxillary structure is installed at the bottom of one end of the connecting bridge.Under the projection of the bridge is the multi-elevation roof of the single and double basement,and the construction conditions are complex.At the present stage,the research on lifting construction mainly focuses on the theoretical and practical analysis of the overall lifting of connected structures with small span and light weight.However,there is no complete set of key technique research and application results for the construction of ultra-long and overweight connecting bridges with the above unconventional structural characteristics and various external complex environments.After a comprehensive analysis of the key and difficult points of steel bridge construction,combined with the existing case studies of upgrading construction in the industry,It had innovated and developed a set of key techniques for dynamic forming construction of large-span special-shaped steel connecting bridges,including linear control technology for dynamic forming of large-span special-shaped steel connecting bridges,internal force control and stress monitoring technology for large-span special-shaped steel connecting bridges,and hazard source control technique for assembly construction of large-span special-shaped steel connecting bridges under complex working conditions.
In the process of dynamic forming of special-shaped steel bridges,the axillary structure is installed step by step,which makes the center of gravity of the structure change continuously,which poses a greater challenge to the linear control of the structure forming.The 150 m long span bridge is assembled into a whole by multiple sections of thick plate steel components,and is dynamically formed by stage lifting.In the process of forming,the internal force is constantly redistributed,so the internal force control and real-time monitoring in the construction process are very important.In addition,the bridge volume is large,most of the components of the single weight of 300 kN,its assembly construction for large lifting equipment demand and projection of the basement roof below the relatively weak bearing capacity of the contradiction between the construction safety hazard source control technique put forward higher requirements.In this technique,asymmetric prearch technique was proposed,welding sequence optimization was optimized,cycle preassembly and virtual preassembly were applied,and the alignment control problem of asymmetric super long bridge was solved.With the application of full-cycle simulation,the lifting system of "multiple lifting points distribution and the combination of main and passive forces" was developed,and the stress discrimination standard of "difference value method" was developed,which solved the problems of structural internal force and stress monitoring in the construction process.The floor reinforcement of "steel support+post-pouring cap" was put forward,and the multi-elevation assembled platform system was developed to ensure the construction safety.