Study On Space Force Behavior Of Large Span Skew Frame Underpass Bridge During Pushing Construction

Underpass frame underpass bridge is a common form of highway crossing railway.Jacking construction is widely used in recent years on the premise that it can be realized without disrupting the traffic of railway operation lines.For across multiple lines,and line height,line spacing,line towards the situation of each different,need to build large section and large Angle and long span skew frame bridge,the pushing process complex,complex structure,further detailed mechanics must be combined with actual situation analysis,to understand and control the spatial behavior of bridge,to ensure the safety of the bridge that have slipped into the pushing process and construction smoothly.In the past,the theory of thick plate is mostly used to analyze the stress of tunnel Bridges,and the results are relatively rough.In this paper,the solid element model is used to simulate the long-span skew frame underpass bridge,and the spatial force and deformation process in the jacking construction are analyzed in detail.Based on Lanzhou-Lianyungang Railway Interchange Project of Jingjiu Road in X i’an,this paper introduces in detail the jacking construction technology of skew frame underpass bridge,the steps of establishing model by entity unit software,the influence of angle and width of skew under dead weight on skew underpass bridge by entity unit model analysis by MIDAS/FEA,and the simulation of jacking construction of skew Underpass Bridge with different long span by entity unit model.During the whole construction process,the influence of static and dynamic loads on the structure during jacking construction is analyzed,which provides theoretical reference and analysis ideas for the same type of underpass bridges.Major research achievement as follows:(1)According to the project,the jacking construction technology is elaborated in detail,and the concrete construction methods and techniques suitable for the project are put forward.(2)The solid element model is established,and the influence of oblique angle and width on the structure is analyzed.The variation of stress and displacement along the span direction with oblique angle and width is obtained,and then concluded the dangerous oblique angle.The results show that the stress value of the whole structure is larger when the angle of oblique intersection is 10 ～30.The displacement value of the vertical node increases continuously between 0 and 20 under the action of dead weight.The vertical displacement is the largest when the angle of oblique intersection is 20 and the influence of the width change on the structure is smaller whether orthogonal or oblique.(3)A three-dimensional beam element model of railway reinforcement system is established to analyze the structural support reaction of overhead system under static and dynamic train loads.The support reaction is used as the force of railway reinforcement system on frame underpass bridge during jacking construction.(4)Establish shape under the rules and less wear line 1 # framework underpasses,simulated in activity line after another wall reinforcement load and one thousand jins forces under the joint action into the whole process of construction,overall structure and the distribution of stress and displacement of the local area and the change rule.The results show that the loading law of static and dynamic lines is the same.The stress and joint displacement of the roof along the railway direction increase with the increase of the jacking distance.There is a large concentration of tensile stress in the sharp Angle area where the bottom slab and the side wall intersect,and a large concentration of compressive stress in the obtuse Angle area where the bottom slab and the vertical wall intersect.The force on the bottom slab has little to do with the top end,which is only related to the layout of the jack.(5)Set up under the irregular shape,size and wear two railway lines 5 #framework underpasses,simulation of structure under the action of gravity and the static line reinforcement load common structure into the whole process of construction stage,obtain structure in jacking construction of structure stress and node displacement in the process of distribution and change rule.Results show that when the structure through a share in a railway line structure away from jack arrangement along the side span direction stress and displacement of whole presents the tendency of decrease with the increase of top range,when through 2 strands of railway line is a line of all lines in the structure of roof structure reinforcement load stress and displacement are increased,but the growth rate is smaller.At the beginning,the structure bears the line load and before jacking into emplacement,that is,when the load ACTS on the edge of the structure,the force on the structure is relatively large.Therefore,the situation that the upper line load ACTS on the edge of the structure should be strictly controlled to avoid large area damage of the structure.