| The steel-concrete composite girder bridge,which can give full play to the strength of different materials,has the advantages of good spanning capacity and overall economy,has been widely valued once put forward,and has been widely used in highway bridges.In recent years,with the rapid development of China’s railway construction,especially the high-speed railway construction,steel-concrete composite continuous girder bridges are gradually applied to high-speed railway bridges.However,due to the large load and obvious dynamic effect of high-speed railway which has strict line smoothness requirements,especially as the main beam structure on the arch,it has a high technical difficulty,while the relevant research at home and abroad is less.The main bridge of Youshui bridge in Furong Town of Zhangjiajie-Jishou-Huaihua railway is an unsymmetrical steel tube concrete arch bridge with a span of 292 m and a design maximum speed of 350 km/h.It is a double track composite girder arch bridge.It is a rare high-speed railway bridge designed with large-span unsymmetrical composite structure arch in China.Among them,the steel-concrete composite continuous girder structure is affected by the arch structure,which is in a relatively unfavorable stress state under the load including the live load of the train.Its stress performance will directly affect the main girder of the bridge and even the working state of the whole bridge,which is a research focus and difficulty of the Youshui bridge of the Zhangjiajie-Jishou-Huaihua railway.In this paper,based on the engineering background of Youshui bridge of Zhangjiajie-Jishou-Huaihua railway in Furong Town,the static force analysis and model test research on the steel-concrete composite continuous girder on the arch are carried out.The main research contents,methods and results are summarized as follows:This thesis analyzes the most unfavorable working condition and position of steel-concrete composite beam of Youshui bridge in Furong Town of Zhang-Ji-Huai railway,establishes the most unfavorable beam space finite element model with ANSYS finite element software,and analyzes the stress state and deformation characteristics of each component of composite beam.The results show that the overall stress level of the structure is low,the maximum compressive stress of the concrete is not more than-8.34 MPa,the tensile stress is basically less than 3.0 MPa,the maximum tensile stress of the steel beam is129.65 MPa,the maximum compressive stress is-138.06 MPa.the stress state of the steel-concrete composite continuous beam is the most unfavorable under the condition of the maximum negative bending moment;the slippage of the stud is not more than 0.143 mm,which has enough safe storage.The maximum shear lag coefficients of concrete top slab and steel bottom slab are 1.341 and 1.108 respectively,which show obvious difference in transverse distribution.Under all working conditions,the stud stress is not more than 66.87 MPa,the slip is less than 0.mm,and it is in elastic working state.As a whole,the steel-concrete composite beam has good mechanical and load-carrying performance,and the steel-concrete cooperative work performance is good,which meets the technical requirements of high-speed railway bridge operation.According to the structural characteristics,stress and force transmission mode of steel-concrete composite girder of Youshui bridge in Furong Town of Zhang-ji-Huai railway,the influence of parameters such as width,thickness of steel top plate and stud arrangement method on the mechanical properties of the structure is analyzed by using the control variable method.The results show that when the width of the steel roof increases from 900 mm to 1800 mm,the average tensile stress of the concrete slab increases by 12%,and the average stress of the steel bottom plate decreases by 0.48 MPa.It can be seen that when the rigidity of the concrete slab is large,the proper reduction of the width of the steel top plate will help to reduce the tension of the concrete slab and give full play to the strength of the steel girder,when the thickness of the steel top plate increases from 24 mm to 40 mm,the steel top plate will increase from 24 mm to 40 mm The vertical deformation of the slab is reduced by 0.009 mm.It can be seen that increasing the thickness of the steel top plate is conducive to reducing the out of plane deformation of the top plate and ensuring the rigidity and strength of the studs.The uniform arrangement of studs makes the stress distribution of beams more uniform along the longitudinal and transverse directions,while the cluster arrangement improves the local strength requirements of the structure;The maximum shear lag coefficients of the concrete top slab under the above arrangement conditions are 1.244 and 1.341 respectively,while the influence of different bolt arrangement modes on the overall stress of the composite beam is limited,and the stress changes of the concrete top slab and the steel bottom slab are not more than 0.121 MPa and 8.19 MPa respectively.(3)In order to verify the actual mechanical performance of the steel-concrete composite girder of the Youshui Bridge in Furong Town of Zhang-Ji-Huai Railway,based on the finite element simulation analysis,the programme of static load model test of the girder was designed,and the similarity ratio was determined to be 1 : 2.5 full-section model.the corresponding test loading program and test program are determined.Through the finite element analysis of the test model,the stress and deformation state of each component under the basic working condition of the model are analyzed.Compared with the calculation results of the original structure finite element model,it can be seen that the stress level and distribution state of the two models are basically the same,and the relative error of the stress of the equivalent measuring point is basically less than 10%.It shows that the equivalence between the test model and the original composite beam is good,and the proposed test model can reflect the main stress state of the original structure. |
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