Study On Temperature Effect And Structural Optimization Of Steel Concrete Composite Beam For Medium And Small Span Railway In High Altitude Mountainous Area

With its light weight,I-steel-concrete composite beam can meet the requirements of seismic design in western mountainous areas.It has simple structure,can be suitable for assembly construction,short construction period,and relatively balanced durability and maintenance cost.Therefore,it has become one of the preferred schemes for railway construction in western mountainous areas.High altitude mountainous area has the characteristics of large temperature difference and high radiation in the daytime.The temperature field and temperature effect of railway composite beam in high altitude mountainous area are not clear.There are few researches on the parameter design of railway composite beam in high altitude area.In this thesis,a high altitude mountain railway composite beam as the engineering background.The temperature field,temperature effect and structure optimization of steel concrete composite beam for medium and small railway in high altitude area are studied.The main contents and conclusions are as follows:Firstly,the research results of composite beam simulation analysis,temperature field,temperature effect and structural parameter optimization are reviewed,and the calculation theory is combed,and the three dimensional refined model of small and medium span steel concrete composite beam considering slip is established,which provides the basis and foundation for the later analysis;Then,the meteorological and geographical parameters of typical high altitude areas are counted to determine the values of general meteorological and geographical parameters of high altitude areas.Through the ANSYS two dimensional finite element thermal analysis model,the temperature field of railway composite beam in high altitude areas is obtained.At the same time,the influence of daytime temperature difference,solar radiation intensity and concrete thickness on the temperature field of railway composite beam is studied,The characteristics of temperature field of railway composite beam in high altitude area are obtained,and compared with the temperature field specified in Code for Design of Steel Concrete Composite Bridge(GB 50917-2013)and Code for Design of Railway Composite Beam(TBJ 24-89).The results show that the temperature field of composite beam is affected by the daytime temperature difference,solar radiation intensity and the thickness of concrete slab;The maximum temperature of railway composite beam is higher in high altitude area with large temperature difference and high radiation than in low and medium altitude area,and the temperature difference between concrete slab and steel beam is larger;There are some differences between the temperature field of high altitude area and that of domestic standard;Then,the temperature field of railway composite beam in high altitude area and ZKH train load in normal use stage are loaded on the three dimensional composite beam finite element model.The temperature effect of railway composite beam in high altitude area is analyzed,and the influence of daytime temperature difference and solar radiation intensity on it is studied.The difference between them is obtained by comparing with the temperature effect under temperature gradient in domestic code.The results show that the temperature effect caused by high altitude environment can not be ignored;In high altitude environment,the deflection of railway composite beam,the maximum tensile stress of concrete slab and the longitudinal relative slip of outer studs near the beam end are greater,but the influence on the maximum tensile stress of steel beam and the longitudinal relative slip of inner studs near the mid span is not significant;The design of composite beam in high altitude area can be carried out according to the current codes;Finally,the influence of concrete slab thickness,steel beam upper flange thickness and width,steel beam lower flange thickness and width on railway composite beam deflection,beam end angle and concrete slab stress in high altitude environment is studied.With the structural mechanical response as the objective,the recommended range of each parameter is given,and the optimization model is established.With the cost as the objective,the optimal parameter values are given.Under the optimized parameters,the railway steel concrete composite beam can meet the requirements of strength and overall stiffness in high altitude environment.