Study On Mechanical Performance Of Cross-layer Heavy Load Truss Of A Railway Station

In the past ten years,the development of steel structures in railway stations has become more large-scale and complicated,and more attention has been paid to their safety,The research on the key problems of structure through the aid of tests,numerical calculations and other auxiliary means is an important technical measure to guarantee the safety of structural design.Combined with the main structure of Daqing West Railway Station,the key stress problems of the cross-layer heavy truss on the side of the main station are studied.The main research content is as follows:1.Through the pushover analysis of two horizontal orthogonal directions,the static elastoplastic performance of the cross-layer truss and its neighboring heavy-duty floor cover is studied(Chapter 3)..The results show that the anti-nappe ability of the X direction is better.Under the influence of X-direction earthquakes,it can meet the design requirements of "small earthquakes are not bad,medium earthquakes can be repaired,and large earthquakes can not fall";The anti-pushover ability of the Y direction is relatively weak,especially when the plastic hinge of some members in B area appears earlier,When the interlayer displacement Angle is 1/70,the component has entered the collapse stage,and the limit value of the displacement Angle between the standard elastic-plastic layer is 1/50,which shows that Y is insufficient to resist the thrust.It is recommended that the structure be strengthened at the Y level to resist the pushover capacity.A lattice column on both sides of a railway station is a weak component.The plastic hinge appears early and the plasticity develops rapidly.The development order of the plastic hinge is the Pillar foot —vertical member —Horizontal component;The plastic hinge first appeared in the middle position of the lattice column under the action of the X seismic force.Due to the reasons of its own structure and the needs of the shape,the lattice column has become a weak link;The lower chord member of the cross story truss is a weak member,and plastic hinge appears earlier..The lower string gradually develops from the middle of the lower string to the left and right sides.Under the limit state,the plastic joints at both ends of the lower string enter the collapse stage.The reason is that the heavy load tower cover connected to the string rod under the cross truss has a "drift effect" under the horizontal load,and the horizontal constraint is relatively weak.It is suggested that the heavy load tower cover connected with the lower string part of the cross truss should be increased.The horizontal support of the building cover enhances its horizontal stiffness.The facade of the B area is the composite structure of the steel members and the wall at the bottom of the cross story truss..The stiffness of the two structures is quite different,resulting in the deformation of the steel member being constrained,and there is a significant stress concentration.At the same time,the stiffness of the wall's anti-lateral force can not be effectively exerted to the maximum effect.Under the influence of horizontal push force,the site becomes a weak link and the plastic hinge is densely distributed2.The three typical nodes of the cross-layer truss are studied by using the numerical calculation of the mixing scale(Chapter 4).The results show that the failure of the node is marked by the failure of the loading terminal part near the connection position of the hub node.The plastic deformation of the loading terminal part does not go deep into the node domain,indicating that the strength of the node is higher than that of the rod part.Under typical adverse load composition,the equivalent stress of the node structure meets the requirement of material design strength.The concrete in the boundary constrained position of the3 # node structure often has a local stress concentration phenomenon in a small area,.However,from the point of view of stress gradient and stress distribution,there is no obvious plastic expansion phenomenon.The reason for the analysis is that it may be caused by the fault of stress integral of individual nodes caused by boundary constraints in the numerical simulation of substructures.This is difficult to avoid in the complex numerical simulation process,but it does not affect the judgment of the bearing capacity of the node area.In addition,the actual node structure is more complex,resulting in the inevitable concentration of stress,and it may also be one of the reasons.Because the residual stress of welding has no influence on the static performance of the joints,the residual stress is not considered in calculation,but the residual stress of the welding may cause the acceleration of the plastic development of the joints,even the brittle fracture will be caused by the dynamic load.It is suggested that the welding remnants should be considered to eliminate the welding residual in the actual working time.Methods and measures of stress.