Analysis Of Mechanical Characteristics Of CRTS Ⅲ Slab Ballastless Track Structure On Bridge Under Complex Loads

The existing high-speed railway in China has entered a new era of rapid development.CRTS Ⅲ slab ballastless track structures are used on high-speed railway bridges in major areas of China.The rapid development of high-speed railways has also brought a series of problems and challenges.At present,the track structure on high-speed railway bridges basically adopts ballastless tracks,and during the actual service of railway bridges,the beam body and track structure are in the atmospheric environment,and their parts will not only change due to their own material characteristics,but will also change with The ambient temperature and other external conditions change.Then it is very important to study the temperature effect of concrete box girder and the effects of temperature load,concrete shrinkage and creep load,bridge pier settlement and beam geometry under the influence of bridge pier settlement.Therefore,a bridge temperature effect model and a track-slab-bridge interaction force calculation model were established to analyze and study the mechanical characteristics of CRTS Ⅲ slab ballastless track on the bridge.The engineering community is very concerned about the effects of the force and deformation of the ballastless track on the bridge under complex loads during service.The main research contents of this article are as follows:(1)Real-time temperature stress analysis of CRTS Ⅲ slab ballastless track on bridgeAiming at the basic characteristics of sunlight temperature distribution of the ballastless track structure on the bridge,a three-dimensional real-time temperature field numerical calculation model of simply supported box girder was established based on meteorological parameters and thermodynamic parameters,and the real-time temperature distribution of the track structure was obtained.Under the effect of solar radiation,the vertical temperature difference at the midline cross section of the box girder changes greatly,and the horizontal temperature difference of the roof is small.The vertical temperature gradually decreases from bottom to top and then gradually increases.The temperature distribution of the top and bottom plates is high,and the abdomen The board temperature is the lowest.At the same time,the world’s universal highway bridge design codes and the analysis results of the real-time calculation of the box beam temperature effect under the unique climate conditions in Sichuan-Tibet region were curve-fitted,and the results were compared and analyzed to obtain the main selection options for the temperature load loading of railway bridges in the Sichuan-Tibet line.Refer to the British BS5400 design code and China’s railway code design code.(2)Analysis of the mechanical characteristics of the seamless track on the bridge under the influence of complex temperature loads and the influence of the track geometryCombined with the calculation results of the actual temperature field,based on the interaction mechanism between the ballast and the ballast of the ballastless track,a detailed analysis model of CRTS type Ⅲ unit slab ballastless track on the bridge was established to carry out the acceptance of the seamless track under complex temperature Analysis of force and deformation characteristics,and analysis of track geometry position.In summer,the most severe loading mode should be considered when designing the bearing capacity of the seamless line: vertical temperature gradient loading mode.The calculation of the design track line in winter is that the lateral loading method is more suitable.For large-span continuous beam bridges,it is recommended to use the real-time uneven temperature difference loading mode for inspection.Under complex temperature loading conditions,temperature has the most obvious effect on the high and low deviations.Therefore,the geometric shape and position cannot be ignored when performing CWR calculation,especially the high and low deviations.Therefore,it is recommended that after the longitudinal force analysis is applied to the already designed seamless line,the geometry and position of the track should be reviewed and checked to ensure the safety quality of the line.(3)Analysis of mechanical properties of CRTS Ⅲ slab ballastless track on bridge caused by shrinkage and creep of bridgeA detailed analysis model of CRTS Ⅲ unit slab ballastless track on the bridge is established,the influence of bridge shrinkage and creep on the geometry and position of the track and the analysis of the mechanical characteristics of the track structure by bridge shrinkage and creep are analyzed.As the contraction of the bridge is also a long-term accumulation process,with the increase of time,the impact of the contraction of the bridge on the deformation of the track structure gradually increases,and the effect on the long-span continuous beam bridge is more obvious;the creep of the concrete stresses the track structure The situation has obvious influence,and with the increase of time,the stress of the track structure becomes more serious,but after 5 years of creep,the stress situation obviously develops toward a stable trend;at the same time,in the process of long-term shrinkage and creep of concrete bridges Among them,the effect on the gauge deviation is the most obvious.When the concrete just undergoes shrinkage and creep,but the geometric deviation is the largest,this shows that creep has an advantage for the project.Creep can cause the redistribution of internal forces in the structure.For the stress concentration area and the uneven settlement of the foundation The local stress generated by the system has a reducing effect,effectively reducing the occurrence of shrinkage cracks.(4)Analysis of the force and deformation of CRTS Ⅲ slab ballastless track on the bridge caused by the settlement of the pierEstablish a spatial line-bridge-pier integration model.When analyzing the deformation of the rail caused by the bridge pier settlement,a variety of calculation conditions are set up to analyze the influence of the bridge pier settlement on the track geometry and the effect of the bridge pier settlement on the track structure mechanics.Characteristic analysis.The settlement of the simply supported beam span has a slightly greater impact on the track structure than the side span settlement;the settlement of the adjacent span has a more serious impact on the track structure;the pier settlement has the most obvious trend in the longitudinal change of the track;at the pier settlement,the rail surface on the bridge The deformation amplitude is the largest in the mid-span position.The larger the settlement amplitude,the greater the deviation of the geometric shape.The height deviation has exceeded the limit when the pier settlement is 5mm,and the pier settlement of 15 mm and30mm has the most serious impact on the track surface irregularity.When designing the CWR,the impact of the pier settlement on the track geometry should be considered,especially the height and uneven track gauge should be evaluated.The settlement of bridge piers has a serious impact on the mid-span section of continuous beams.For the track geometry,the settlement of the pier at the end of the continuous beam has a greater impact on the deformation of the rail surface than the settlement of the middle pier of the continuous beam.The difference between the uneven settlement of the bridge pier and the settlement of the single pier is not much,mainly depends on the relative difference of the settlement of the pier: the greater the relative difference of the settlement,the greater the impact on the irregularity of the rail surface.In the design and supervision of the seamless line,the geometric irregularity of the rail surface mainly considers the high and low deviations,and special attention should be paid to the settlement of the beam end.