Study On The Mechanical Properties Of Railway Continuous Channel Girder Bridge

In recent years,the rapid development of China’s railways has promoted economic development and facilitated people’s lives,but it has also brought many problems.The channel girder bridge belongs to the through-type open thin-walled structure,which has obvious advantages over the traditional structure: the main beam on both sides can not only play the role of anti-collision,but also effectively isolate noise,and the design of the throughtype track bed plate reduces the elevation of the pavement or track.At the same time,it is easy to arrange various communication equipment inside the bridge,which greatly improves the safety and comfort of driving.Therefore,the channel girder is suitable for areas with special requirements such as limiting the building height and controlling environmental noise,especially in the case of disease treatment of existing railway lines in mountainous areas and close to the station yard.Due to the limitation of line elevation,the channel beam has great application potential.In this paper,a single-track railway continuous channel girder bridge is taken as the research object,and the mechanical characteristics of the bridge are studied.The main research work is as follows:(1)Combined with the actual situation of a bridge project,the finite element simulation of the channel girder is carried out,and the fine finite element model of the continuous channel girder bridge is established.The deformation of continuous trough beam is studied,the proportion of the longitudinal bending moment shared by the main girder and the deck slab is calculated,and the difference of the proportion of the longitudinal bending moment shared by the main girder with different sections is analyzed.The calculation results show that the deflection of the lower edge of the middle section of the main span produces the maximum deflection near the center of the lower edge of the deck slab,and the main girder inclines to the groove near the middle support,and the main girder presents the lateral deformation of the outer slope near the side support and the middle position of the main span.Under the action of dead load and live load,the ratio of the longitudinal bending moment borne by the main girder and deck slab sections in the middle of the main span is 1.41:1,and the ratio of the longitudinal bending moment borne by the main girder and deck slab sections in the two middle support sections is 3.78:1 and 4.00:1,respectively.Under the same load,the longitudinal bending moment bearing ratio of main girder and deck slab with different sections is positively correlated with their vertical bending stiffness.(2)The stress distribution of continuous channel girder bridge is studied,in which the stress of its control section(side bearing section,middle bearing section,main span cross section)is mainly analyzed,and the stress concentration and the most unfavorable position are finally found.The analysis results show that Under the action of dead load and live load,the position of the main beam diaphragm is more complex,and it is easy to produce tensile stress,but the tensile stress is small at this time.The section of the channel girder is an open section,and the stress concentration is easy to occur at the junction of the main girder and the deck slab.This is a weak position,and the local stress can be reduced by adding reinforcement.(3)Analyze the shear lag effect of continuous channel girder bridges,determine the shear lag coefficient and effective width of the simplified calculation of the deck slab,and then propose a simplified calculation model for the channel girder bridge.The analysis results show that under the action of dead load and live load,the positive shear lag phenomenon mainly occurs in the longitudinal direction of the channel girder near the middle support,while the negative shear lag phenomenon occurs near the side support and the middle of the main span.The positive shear lag effect occurs at the center line of the top deck and at the junction of the bottom deck and the main girder in the mid-span section;for the midsupported section,the positive shear lag effect occurs at the junction of the top deck and the web and at the center of the bottom deck.The final calculation of the recommended values for the effective width ratio of the deck slab of a continuous channel girder bridge under constant+ live load is taken as 0.83 in the section near the middle of the main span,1 near the side bearing section and 0.74 near the middle bearing section.(4)Stress control during construction and design optimization of continuous channel girder bridge.The stress and deformation of continuous channel girder bridge under cantilever pouring construction are analyzed,and the construction camber is obtained to guide the construction.Analyze the most economical section under different spans,and optimize the design of continuous channel girder section to find the deck slab thickness(height)value for construction safety and traffic safety.The calculation results show that the maximum static live load deflection of the midspan of the continuous channel girder bridge is 17.8 mm,the maximum tensile stress in the construction stage is 0.4 MPa,and the maximum compressive stress is-8.2 MPa,all of which meet the requirements of the specification.When the span is less than 72 m,the box main girder and slab deck slab are the best economic choice.At the same time,the optimal parameters of the continuous channel girder bridge are calculated:when the bottom width is 9.0 m,the upper flange width is 2.0 m,the side girder web width is1.5 m,the deck slab height is 1.3 m and the girder body(side support)height is 2.5 m,the dead weight and cost are the minimum.