Research On Spatial Effect Of Steel-prestressed Concrete Continuous Beam Bridge

Steel-prestressed concrete composite structure combines the advantages of steel structure and prestressed reinforced concrete structure, it has become a new type of structure, which is widely used in bridge engineering. Steel-prestressed concrete composite continuous box girder bridge connects the steel box girder with concrete box girder through the steel-concrete joint, steel box girder connects with concrete deck slab through the shear connector. Under the imposed loads, the composite continuous girder bridge, in addition to pulling, pressure, and bending, shear and torsion deformation, has some spatial effects such as slanting load effect and shear lag effect, at the same time steel box girder, as a thin-walled structure, has the global and local stability problems.The paper is based on the background of the G318in Changing County, State Road Changqiao Bridge, and combines with the practical characteristics of the bridge, focuses on the related research about spatial effects of the steel-prestressed concrete composite continuous box girder bridge, including the following aspects:(1) Combining the present domestic and foreign research situation on the steel and concrete composite beams, this paper expounds the following aspects of the spatial effects:slanting load of bridge, load effective distribution width of box girder, buckling of steel box girder. According to the question needed to study, established spatial plate and shell element model.(2) In order to study the slanting load effect of bridge, according to the bending moment influence line of characteristic sections, load the three kinds of lanes load, and study the load mechanical response in the symmetrical and slanting load; according to the stress and deformation of the vertical deflection of each section, study its the slanting load effect, and calculate. The analysis results show that, for the slanting load coefficient of concrete box girders, can use experience value method, and it has certain security reserves, but for steel box girder,cannot directly use the experience value method, need a specific calculation to determine.(3) Calculating the law to the normal stress in bridge with each characteristic sections under the action of dead weight, and analyzes its horizontal non-uniform distribution regularity, it is found that each characteristic section have the different degree of shear lag phenomenon, in the pivot point it is relatively obvious. And according to the bridge specification, calculates the effective distribution width of each characteristic section, and compares with the actual stress graph,it is found that two widths are very close, showing that it is consistent with the reality according to the effective distribution width through the specification calculating method.(4) Analyzes the buckling effect under the dead weight load, and obtain the buckling characteristic value and buckling modes. The analysis shows that, because of the large stiffness of concrete beams, instability won’t happen, buckling occurs mainly in the midspan of the steel box girder.