Study On The Key Technology Of Long Cantilever And Closure Of PC Continuous Rigid Frame Bridge With Super Multi-span And High-pier Under Adverse Conditions

In order to strengthen the protection of the ecological environment,prevent mountain excavation,the prestressed concrete(PC)continuous rigid frame bridge with super multi-span and high-pier(five span and above)is widely used in the bridge construction in the western mountainous area due to its strong overall span capacity.However,the cantilever work of continuous rigid frame bridge with super multi-span is heavy and the construction period is very long.Thus,there are many unforeseen factors caused by emergencies such as climate conditions,environmental disasters and epidemic situation in the construction period,long time stagnation of cantilever and closure process.As a result,the actual construction period of this type of bridge far deviates from the normal construction period.There are "stagnation" in the process of cantilever and closure and "rush for construction period" in the environment of strong sunlight and large temperature difference.Therefore,how to solve the adverse effects of long lag period,strong sunlight and large temperature difference in the long cantilever and closure process is inevitable.It is very important to study the key technology in the whole process of long cantilever and closure of PC continuous rigid frame bridge with super multi-span and highpier under adverse conditions(long lag period,strong sunlight and large temperature difference).This paper relies on the basic research plan of natural science of Shanxi Province(2018JM5018),taking the PC continuous rigid frame bridge with seven-span and high-pier in the western mountainous area as the engineering background.The model of adverse conditions in the whole process of long cantilever and closure of the bridge is established,including long lag period model,strong sunlight and large temperature difference environment model.The effects of adverse conditions on the mechanical property of long cantilever as well as the closure method and the closure top thrust of PC continuous rigid frame bridge with super multi-span and high-pier is studied,then the key technology of the cantilever and closure process of PC continuous rigid frame bridge with super multi-span and high-pier is put forward.The main research contents are as follows:(1)The numerical prediction model of PC continuous rigid frame bridge with super multi-span and high-pier is established.The adverse conditions in the whole process of long cantilever and closure of the continuous rigid frame bridge is analyzed,and the adverse condition model is established,including long lag period model,strong sunlight and large temperature difference environment model.The effects of adverse conditions on the mechanical property of long cantilever of PC continuous rigid frame bridge with super multi-span and highpier is studied.Moreover,the long cantilever deformation prediction formula of PC continuous rigid frame bridge with super multi-span considering the height of pier body in the western mountainous area with strong sunshine and large temperature difference is established.(2)The closure method and process of PC continuous rigid frame bridge with super multispan and high-pier under the most unfavorable conditions is studied,then the optimal closure method considering horizontal displacement of pier top,bending moment of pier top and pier bottom,vertical displacement of main beam and stress of upper and lower edge of main beam as the control target is established.(3)A multi-target control system considering the section stress,pier body stress and vertical displacement of the main beam is established,then a calculation method of jacking force based on the optimal closure method to obtain a reasonable jacking force is proposed,and compared with the single target control.The formula of closure top thrust of PC continuous rigid frame bridge with super multi-span and high-pier considering adverse conditions is given.