Research On The Static Performance Of Twin-Ⅰ Steel-Composite Girder Bridges With Precast Concrete Deck Panel

With the in-depth study of the steel-composite plate girder,the structural system of the traditional steel-composite plate girder bridges has been greatly simplified.The twin Ⅰ-girder steel-composite plate girder bridge has become the mainstream of the new medium-small span bridge,which is considered to be an extremely economical bridge form.Due to the large spacing of the main girder of the Twin-Ⅰ girder steel-composite bridges with precast concrete deck panel,the transverse effect of the bridge is obvious.And the economic performance research on the twin Ⅰ-girder bridge in China is also insufficient.The technical-economic and transverse mechanical performance of the bridge has become the two major factors restricting the development of such bridges.This paper summarized the structural forms and design points of assembly steel-composite plate girder bridges,carried out preliminary design for 3×35m twin Ⅰ-girder bridges.And compared the economic performance of steel-composite plate girder bridge with precast concrete deck panel,steel-composite box girder bridge and assembled concrete small box girder under the same span and the same stress level.Finally,based on the steel-composite plate girder bridge with precast concrete deck panel test,the full-bridge finite element simulation is carried out to analyze the transverse mechanical performance of the full bridge under live load such as eccentric load and overload.The main research contents are and conclusions summarized as follows:(1)The development advantages and promotion significance of steel-composite plate girder bridge in medium-small span bridges are described.And summarize the research status and the deficiencies of precast concrete deck panel-steel-composite plate girder bridge.Under the idea of assembly considering the convenience of construction,the main structure and design details of the steel-composite plate girder bridge are summarized.(2)MIDAS finite element analysis is carried out for 3×35m steel-composite plate girder bridge,steel-composite box girder bridge and assembled concrete small box girder.The economic performance of the three schemes are compared based on the equivalent mechanical performance of the three bridge types,consider the full life cycle cost.The study shows that when considering the conditions of bridge maintenance,demolition and recovery,the cost of steel-composite plate girder bridge is obviously better than that of assembled concrete small box girder bridge,and assembled concrete small box girder bridge is 3.64% higher than it.(3)Through the single girder test and finite element analysis of precast concrete deck panel-steel-composite plate girder,it is found that such bridges have good ductility,and the shear studs are simulated by springs to simulate the whole mechanical performance of the steelcomposite plate girder.Eight models of different shear stud layouts is analyzed.It is concluded that the spacing of the shear pockets can be expanded to 1200 mm under the clustered shear stud design.Within 1200 mm,the bearing capacity of the test specimen is reduced to less than 4.0%,while the stiffness of specimens in the elastic working range does not decrease significantly.(4)Based on the analysis of the mechanical performance of the bridge under live load,it is suggested that the transverse distribution coefficient of the two girders can be approximated to 0.9 and 0.1.When the standard vehicle is used for loading,the maximum stress and deflection of its critical position are not much different from those in the design of 1.5 times lane load.Considering the randomness of standard vehicle loading,so the bridge design can adopt 1.4 times live load coefficient.When the three times standard vehicle load is used as overloaded vehicle,the strength,stiffness and stability still meet the demand under the condition of eccentric load and overload.