Analysis On Mechanical Characteristics Of Steel-Concrete Composite Grider Of Suspension Bridge

Steel-concrete composite girder is a new type girder, which is developed based on the foundation of steel structure and concrete structure. At present, it has been widely used in long-span continued girder bridges. Lancangjiang Bridge is the first long-span suspension bridge with composite girder as stiffening girder. The thesis analysizesd the mechanical characteristics of steel-concrete composite girder of Lancangjiang Bridge.The thesis simply reviewed research actualities of steel-concrete composite girder in our country and abroad, and presented the mechanical feature of nonlinear of long-span suspension bridge, the static calculation theory and general calculation principle of composite girder.Three dimensional structure of Lancangjiang Bridge was analysed and researched. The general finite element analysis programme ANSYS and Bridge Nonlinear analysis system BNLAS are used as analysis tools. Calculating model was built for simulating stiffening girder's structural response in various practical load conditions.Simplified elastoplasticity assumption and Von Mises yield criterion and correlate flowing criterion are adopted, and elastic development is also considered in the thesis. The following three loading conditions were taken into account:(1) dead load + the most disadvantageous vehicle load situation which produce maximum moment of stiffening girder.(2) dead load + the most disadvantageous vehicle load situation which produce minimum moment of stiffening girder.(3) dead load + the main span is fully distributed with pedestrian load.The three loading conditions is analysed in detail. When concrete deck and steel main girder of composite stiffening girder work together, how they share the force, how longitudinal stress distributed along the bridge span orientation, they were calculated and analysed in detail. When shear lag effect is considered, how the longitudinal stress of deck section distributed along transverse. When vihecle load was applied on the girder, how the stress distribution changed. By summarizing the regularity of distribution of deck section longitudinal stress along transverse according to the three respectively load condition, compositestiffening girder's efficient width was calculated with the effect of shear lag , and a proper method and approach to simplify composite beam by beam element was found in building model based on it.Through analyzing mechanical characteristics of Lancangjiang Bridge steel-concrete composite girder obtain some conclusions. These conclusions had some leading significance in designing and checking steel-concrete composite stiffening girder suspension bridge.