Research On New Beam Structure Design And Mechanical Properties Of Continuous Rigid Frame Bridge

In recent years,prestressed concrete continuous rigid frame bridges have been widely used in China,but due to the existence of radial forces,diseases such as floor cracking and mid-span deflection have not been resolved for a long time.Engineers have adopted many methods and have not eliminated the effects of radial forces.In recent years,the concept of a new type of beam body has been proposed,the core of which is to change the prestressed steel beams of the mid-span floor from a curved arrangement to a horizontal arrangement,thereby changing the shape and structure of the mid-span floor.This method theoretically eliminates the radial force generated by the prestressed beam in the middle of the span,and can optimize the deflection of the continuous rigid frame bridge.In this paper,through the numerical simulation method of MIDAS CIVIL,the length and height of the horizontal section of this new type of beam are discussed in depth,and their relationship with the mid-span.Mainly completed the following work:Firstly,based on the development of traditional curves and new horizontal beams at home and abroad,the reasons for continuous rigid frame bridge deflection and low bearing capacity are mainly analyzed.Through theoretical analysis,it is concluded that the structure of the traditional curved bottom plate will produce radial force when the prestressed steel beam of the bottom plate is tensioned,and this force will cause the overall performance of the bridge to decline.And through calculation,the magnitude and change trend of the radial force under different spans of the traditional curve structure are obtained.If the calculated radial force is loaded into the corresponding new horizontal floor structure,the force of the curve floor structure can be simulated situation.Secondly,three sets of continuous rigid frame bridges with different spans(120m,150 m,180m)were established through finite element software.In the case of traditional curve layout and horizontal layout(ie,loading and unloading radial forces),the displacement and The change of load-bearing capacity shows that the deflection and stress conditions of the new beam body are better than the continuous rigid frame bridge with traditional curved floor.Therefore,in continuous steel bridges with different spans,the effect of radial force should be eliminated,and the performance of the new beam body with a calculated span of 150 m should be selected.Then,based on an example of a bridge project,the structural size design of a new type of continuous rigid frame bridge is discussed.On the basis of calculating the span of 150 m,through MIDAS CIVIL,the models of different horizontal section lengths(29m,38 m,47m)and different horizontal section heights(3.5m,4.5m,5.5m)in the mid-span were established for comparison and analysis of bridges.In the later period of mid-span,the vertical displacement,shear force,bending moment and stress combination and other parameters change,the bridge’s reasonable span mid-horizontal floor length should be 38 m,the beam height should be 4.5m,and the reasonable horizontal section length and mid-span calculated span The ratio should be between 1:5and 1:3.5,and the ratio between the height of the horizontal section and the calculated span of the midspan should be between 1:40 and 1:30.Finally,the construction technology of the prestressed steel beam of the new beam bottom plate and the precautions for the horizontal arrangement of the bottom plate steel beam are discussed.And prospects the practical application value of this structure in bridge engineering.