Several Key Problems Research Of Design And Construction For Hybrid Extradosed Cable-stayed Bridge

The extradosed cable-stayed bridge is a kind of bridge which is comprehensive utilization of the advantages of traditional cable-stayed bridge and continuous girder bridge or continuous rigid frame bridge. It has a cable-stayed bridge style, but in the stress characteristic, structure size ratio and the cable layout, there are certain differences with the traditional cable-stayed bridge. At present, the rigid girder extradosed cable-stayed bridge built more, but the high beam size smaller, the beam more soft flexible girder extradosed cable-stayed bridge coordinate with environment more easily, more popular, more development prospects and promotion significance.This paper took the world's largest span hybrid extradosed cable-stayed bridge — Rongjiang bridge as the engineering background, and launched a series of research work around definition of the hybrid extradosed cable-stayed bridge, structure characteristic, analysis of structural parameters, main beam construction scheme and stress analysis of cable-girder anchorage zone with steel box girder. Using the symbols calculation function of the Matlab deduced calculation formula of structure characteristic parameter that could easily define hybrid extradosed cable-stayed bridge. through the finite element software Midas/Civil the whole construction process of finite element simulation model and structural parameter analysis model of bridge were built, through the finite element software FBR_CAL_SUO demonstration and comparison of construction schemes of steel box girder for the secondary side span of Rongjiang Bridge were demonstrated and compared, through the finite element software Midas/FEA local stress of cable-girder anchorage zone were analysed. The main research contents are as follows:(1)The development status of the extradosed cable-stayed bridge was introduced and the research trends of hybrid extradosed cable-stayed bridge were analyzed. Cable/beam live-load ratio as important evaluation indexes of structure characteristic was proposed and the calculation formulas with different boundary conditions and different steel concrete girder arrangement of the hybrid extradosed cable-stayed bridge were deduced.(2)According to the statistical analysis and comparison of bridges, cable/beam live-load ratio is less than 0.5 for the rigid girder extradosed cable-stayed bridge, greater than 0.5 for flexible girder extradosed cable-stayed bridge or traditional cable-stayed bridge.(3)By Midas/Civil finite element software the whole construction process model of Rongjiang bridge was established. analyzes The construction stage and the bridge operational stage were analyzed. According to the structural characteristics of the Rongjiang bridge, a calculation model was established for a plurality of bridge phase models to height of the tower, girder height and auxiliary pier location for the structure changes of parameters using Midas/Civil finite element software. And the structure parameters rationality of practical design scheme for Rongjiang bridge were demonstrated.(4)Two construction schemes of the secondary side span were formulated. One scheme is to assemble the steel box girder by derrick crane, the other one is to make use of the bracket to do the girder assembly. Accordingly, two different finite element models were established by the finite element software FBR_CAL_SUO. From the feasibility, safety, economy and construction control difficulty etc, the comparison of two kinds of construction projects were demonstrated, and the recommended scheme for construction tension and assembled elevation were finally determined.(5)The girder segment with maximum cable force and minimum cable horizontal inclination was selected as the research object. Through the finite element software Midas/FEA local stress of cable-girder anchorage zone of hybrid extradosed cable-stayed bridge with steel box girder were analysed.