Investigation On The Static Performance Of Steel-Concrete Joint Of Integrated Track Beam For Medium-Low Speed Maglev

Medium and low-speed maglev has the advantages of small turning radius,strong climbing ability,high safety,and low noise,and it has become a competitive scheme in the urban rail transit field.Currently,China has the Hunan Changsha line,Phoenix tourism line,Guangdong Qingyuan line,and other medium and low-speed maglev transport lines in operation.Most of the constructed medium and low-speed maglev lines adopt the track beam structure with separated bridge and rail.Such a separated track beam has many problems,such as considerable building height,weak structural integrity,and failure to consider the contribution of F rail stiffness.Therefore,China Railway Maglev Transportation Investment and Construction Co.,Ltd.has proposed two new track beam structures with integrated bridge and rail suitable for medium and low-speed maglev.The two integrated track beams are the transverse through-through and open-hole steel plate track beam structures.To clarify the load-carrying capacity and force transmission mechanism of steel-concrete joints of the above two kinds of rail beam structures,this study implements model tests and finite element simulation analysis and analyzes the main design parameters on the mechanical behavior of the steel-concrete joints.The main research contents and conclusions are as follows:(1)For the beam-rail integrated rail beam,the integral and local finite element models are established,and the mechanical properties of the beam-rail integrated rail beam and its steel-concrete joints are preliminarily defined.Taking the design of 25 m span simply-supported beam of Qingyuan Line as a reference,the global rail system model of track beam was established,and the stress,deformation and natural vibration frequency of separated rail beam and beam-rail integrated rail beam was calculated.The results show that considering the contribution of F rail stiffness,the stiffness of the structure can be significantly improved,and the rail beam height can still meet the design requirements by reducing 50 cm.On the basis of summing up the finite element analysis method of steel-concrete composite structure,a detailed local finite element model of the steel-concrete joint of beam-rail integrated rail beam was established,and the stress and deformation of the two steel-concrete joints under the design load were analyzed.It was proved that the 60% beam height model could replace the complete beam height model for the model test to investigate the local static properties of the steel-concrete joints.(2)The model test for static performance of steel-concrete joint was designed and completed.According to the preliminary finite element analysis results,two local test models of the steel-concrete joint of beam-rail integrated rail beam were designed.Three test models were designed,each containing four steel-concrete joints.The process of making the test model,the arrangement of measuring points,and the way of applying design load were introduced.The experimental loading was completed,and the experimental phenomenon showed that both steel-concrete joints have sufficient strength enrichment,and the strength failure of the concrete beam occurred before that of steel-concrete joints.(3)According to the test and finite element analysis results,the steel-concrete joint’s load-carrying capacity and force transmission mechanism were analyzed.The analysis of the model test data showed that the two steel-concrete joints are in a linear elastic state as a whole within 1.5 times the design load,and the concrete beams crack and fail first under about 5.0 times the design load.The strength of steel-concrete joints can meet the design requirements and have a high richness.The displacement difference between internal and external magnetic poles of F rail meets the design limit under the design load,but the relative abundance is small.The connection should be controlled by stiffness design.The finite element model parameters of the steelconcrete joint were adjusted according to the actual test conditions,and the accuracy was verified by the test data.The force transmission mechanism of the steel-concrete joint was analyzed by using the verified finite element model.The results show that the vertical load transfer in the two steel-concrete joints mainly depends on the bearing action of the steel plate in the joints under the design load level.(4)Combined with model test and finite element analysis data,the influence of design parameters of key structures in two kinds of steel-concrete joints on the mechanical properties of beam-rail integrated rail beams were analyzed.The results show that,in the range of parameters discussed,the stiffness of the steel-concrete joint can be significantly improved by increasing the thickness of the connecting piece roof in the transverse through-through structure.Under the design load,the welding nail is in an elastic state,and its type has little influence on the force transmission.In the openhole steel plate structure,the increase in the thickness of the open-hole plate can improve the stiffness of the steel-concrete joint so that the force transmission is smooth.The open-hole plate connector is in an elastic state,and its design parameters have little influence on the force transmission.