Study On The Mechanical Characteristics Of Long-span Road-Rail Plate-Truss Combine-Suspension Bridge

In recent years,China's infrastructure construction has developed rapidly,especially for the construction of high-speed railways.It is necessary to build more railway bridges in the big rivers and western mountainous areas to meet the needs of national development.The railway suspension bridges with large capacity will gradually become an important choice.However,the two-purpose suspension bridges that have been completed and opened to traffic in China are only the Tsing Ma Bridge in Hong Kong,and the design and construction of the Tsing Ma Bridge are completed by foreign countries.The design,theoretical research,construction management,etc.of the long-span dual-purpose suspension bridges.Therefore,it is necessary to study the influence of the stress characteristics and structural parameters of the suspension bridge of the public railway.This paper takes the construction of the Second Yangtze River Bridge in Lu Zhou as the background of the project.The main work is as follows:(1)The development status of long-span public-rail suspension bridges at home and abroad and the calculation theory of static and dynamics of suspension bridges for railways and railways are reviewed.(2)According to the finite element principle,the full-bridge spatial finite element model is established by software Midas Civil.The force performance of the bridge under the action of near-long-term dead load and near-long-term main force is analyzed to clarify the force characteristics of the full bridge.The results show that the pylon,cable system and truss are reasonably stressed,and the strength and stiffness meet the requirements of the specification.(3)Using the Midas Civil finite element to establish a full-bridge model,the parameters of the long-span railway-rail suspension bridge are analyzed,and the changes of main parameters(vector-to-span ratio,central buckle,and dead load)are applied to live load,temperature load and cross wind load.Under the influence of the force,the law of structural stress and parameters is obtained.The results show that reducing the span ratio of the main cable will increase the structural rigidity,but the structural capacity will gradually increase.The presence of the central buckle can reduce the longitudinal and vertical deformation of the suspension bridge,which is beneficial to the safety of rail transit.The degree of loading can improve the overall stiffness of the suspension bridge,therefore,it is more reasonable to stress the structure under different load effects.(4)The suspension bridge's dynamic performance is the basis of seismic and wind-resistant design and vehicle-bridge interaction.By changing the main cable span ratio,main cable stiffness,main tower stiffness,ballast plate,truss height,truss width parameters,etc.,the sensitivity of the suspension bridge to the dynamic characteristics of the suspension bridge is analyzed and compared,and the improvement of the long-span railway-rail suspension bridge is proposed.Effective measures for dynamic characteristics.The results show that the sagittal ratio and the stiffness of the main cable have a great influence on the vertical bending,and have little effect on other vibration modes.The stiffness of the main tower has a significant influence on the natural vibration frequency of the longitudinal and transverse bending of the main cable;As the width of the board increases,the transverse bending,vertical bending and torsion increase gradually;the height of the raft and the width of the rafter have a greater influence on the transverse bending and the vertical bending.