Studyon Mechanical Characteristicsand Construction Techniquesof Pier-Top Steel Truss Girder Erectionof Cable-Stayed Bridge

The construction of the sea-crossing bridge is of great significance to the national politics,economy and culture.Steel truss bridge is widely used in the current sea crossing bridge due to its light weight and large span capacity.Moreover,the bearing capacity of steel truss bridge is higher than that of reinforced concrete bridge,and it is more suitable for the design of double deck bridge with stronger traffic capacity.During the construction of sea-crossing bridge under the bad sea conditions,the erection of steel truss girder is seriously affected by the strong wind and surge.In the erection of steel truss girder,the steel truss girder on the pier top is the initial section of steel truss girder erection,and its construction quality directly affects the subsequent construction of steel truss girder in other sections.Therefore,it is necessary to study the key construction technology and stress characteristics of steel truss girder erection on the pier top under severe marine environment.Based on the construction of the steel beam on the pier top of Yuanhong channel bridge of Pingtan Straits Rail-cum-Road Bridge,this paper first introduces the bad construction environment and facade layout of the bridge,then introduces the structural form of the steel truss girder section on the pier top and the pier-side brackets,and finally introduces the key construction technology of the steel truss girder erection on the pier top,mainly including the installation of the pier-side brackets and the 4 segments on the pier top.The construction process provides the foundation for the load calculation and working condition determination in the later finite element analysis.In the calculation part,the finite element analysis of the pier-side brackets is introduced during the erection of steel truss girder on the top of main pier.According to the actual construction stage,six construction conditions are selected in the analysis of pier-side brackets,two construction conditions are selected in the analysis of steel truss girder section on the pier top,and the load value and load combination to be considered in each construction condition are calculated.Then the stress state and deformation of the pier-side brackets under various working conditions are analyzed in detail,and the results are summarized and analyzed.According to the calculation results,the strength,rigidity and stability are checked.At the same time,the stress safety of the embedded parts of the bracket is also checked.Through the above checking calculation,the overall structure and construction scheme of the pier-side brackets are verified to meet the safety requirements.After getting the deformation results of the bracket,the stress and deformation state of the pier top steel truss girder segment after the bearing displacement due to the deflection of the slideway beam is analyzed,and the results are checked from three aspects.To sum up,this paper studies the key construction technology and stage stress characteristics of steel truss girder erection on the top of cable-stayed bridge pier under severe sea conditions.First,it describes the construction scheme and key technologies used in the construction of steel truss girder erection.Then,taking the erection of 7 sections of steel truss girder on the top of the main pier as an example,the stress analysis of the pier-side brackets and the section of steel truss girder on the top of the pier under various conditions is carried out through the finite element software.This paper analyzes whether the overall scheme of steel beam erection construction on pier top meets the actual requirements,and puts forward some improvements.