An Analysis Of The Structural And Mechanical Behavior Of Beam-arch Combination Rigid Frame Bridge

Beam-arch composite rigid frame bridge is a new type of structure proposed on the basis of open-web rigid frame bridge.Beam-arch composite rigid frame bridge is a kind of composite structure based on hollow rigid frame bridge,which is obtained by greatly increasing the height difference between upper chord and lower chord structure at pier and the distance between upper chord and lower chord joint point and pier.That makes the structure much lighter.More importantly,the effect of the lower chord "arch" is brought into play,which makes the stress,structural stiffness and crack resistance of this composite rigid frame bridge better.At present,in view of the lack of research on the beam-arch combination structure of the new bridge,this paper takes the Lijia Jialingjiang composite rigid frame bridge in Chongqing as the background to study the.(1)Research on the design of beam-arch combination structure form.It is found that the forces acting on the beam-arch joint is complex.To ensure the structural safety of the joint,three types of beam-arch joint structures are proposed,namely,X-type diaphragm combined structure,A-type diaphragm combined structure and “da”-type diaphragm combined structure.(2)Mechanical properties analysis of different beam-arch combination structures.Three kinds of structural models are established by finite element software,and the stress distribution of the roof,web,floor,diaphragm and diaphragm are compared and analyzed,so as to grasp the mechanical properties of the beam-arch joint in different structural forms.It is found that all the three roofs have obvious shear lag effect along the bridge;all three types of structures can satisfy the compressive characteristics of concrete;special attention should be paid to the sudden change of stress in the area where the diaphragm intersects with the roof,web and floor;by comparing the tensile stresses of various components in different structural forms,it is found that the X-type diaphragm combined structure is not suitable for the bridge type,the intersection position of the “da”-type diaphragm combined structure has adverse effects,the A-type diaphragm combined structure is the preferred form of beam-arch combination structure.(3)Study on structural design parameters of A-type diaphragm combined structure.Taking the A-type diaphragmatic beam-arch joint structure as the object,the stress distribution of different diaphragm thickness,length of middle diaphragm and thickness of upper and lower chord fusion are compared by modeling calculation,and the most suitable structural design parameters of the beam-arch composite rigid frame bridge are obtained.The results show that the structural stress is sensitive to the change of the length parameters of the diaphragm,and that too long or too short is not conducive to the structural stress;the thickness of the diaphragm and the thickness of the fusion of the upper and lower chords have little influence on the structural stress.Comparing the mechanical characteristics and economy of the structure under different parameters,it is found that the thickness of diaphragm is 50 cm,the length of middle diaphragm is 840 cm,and the thickness of upper and lower chord fusion is about 190 cm.