Study On Static And Dynamic Characteristics Of Large - Span Rail-Road Suspension Bridge

The large span suspension bridge is a flexible suspension system composed of main cable and stiffening girder,which has the characteristics of high span capacity,good mechanical performance and good economic effect.It has demonstrated good competitiveness in spanning deep valleys,rivers and channels.The rail-road suspension bridge is a new kind of suspension bridge structure developed in recent years,which is characterized by inheriting the traditional suspension bridge,and has the characteristics of saving land resources and economy.Currently,there are few studies on the rail-road suspension bridge.To ensure the smooth construction and safe operation of the first rail-road suspension bridge in Guizhou province,it is very important to carry out the research on the mechanical properties of the large-span rail-road suspension bridge with the background of the Maling River No.3 Bridge in Xingyi,Guizhou province,which is under construction.Using numerical simulation as the main research method,this paper studied the static and dynamic characteristics of the long-span common rail suspension bridge,and the main research results are as follows:1.Sorting the theory of static calculation and dynamic characteristics of the suspension bridge,including the early theory of elasticity and the theory of disturbance,and the finite displacement and nonlinear finite element theory adopted at present.The basic assumptions of each calculation theory are analyzed systematically.The error reasons of the early theories are analyzed,and finite element theory is used as the theoretical basis for this study.2.Through multiple cable shape calculation theory for the main cable calculation,verified the calculation precision of the finite element software,verified the feasibility of the structural analysis by finite element software and the correctness of the model,and by the linear parameters influence analysis,grasped the important parameters of the main cable shape.The results show that the main cable shape calculation with the current alternative finite element computing platform has high accuracy.The calculation theory,material properties,constant load and temperature field are the main parameters affecting the calculation and erection of main cable.3.Based on finite displacement and nonlinear finite element theory,a finite element analysis model is established for the construction stage of the large-span rail-road suspension bridge in the construction stage.Simulation of the mechanics state of the construction process of the Marling River No.3 Bridge is carried out.The influence of hoisting order and stiffening girder connection scheme on structural mechanical properties is studied by using the main cable elevation,stiffening girder linear,internal force and cable system internal force as the research object.Mastered the main cable under different hoisting sequence,the changing rule of the stiffening girder elevation,analyzed the cable saddle pushing,find out the essence of the cable saddle pushing,and according to the cable tower allowable deviation and stress made the cable saddle pushing scheme,which is applicable to the project.The results show that the vertical displacement of the main cable can be controlled by the construction scheme from the cross to the side.It is advantageous to make the structure reach the ideal bridge state by using the hinged method or section hinged method,which is advantageous to the stress control of the stiffening beam.The thrust of the saddle is to pull the tower back to its vertical position.4.In the operation stage,the static characteristics of the Maling River No.3 Bridge under vehicle load,rail traffic load,temperature effect and lateral static wind effect were analyzed by finite element method.This paper analyzed the full load and half load of the bridge and analyzed the internal force and stiffening beam displacement of the cable system under the corresponding working conditions.This paper points out the stress characteristics of the suspension bridge cable system under the influence of temperature and the effect of the bridge under the transverse static wind load,and demonstrated the safety of the structure under extreme conditions.The results show that the maximum vertical displacement of the structure is near a quarter of the main span under the action of static equivalent moving load.The loading side and the unloaded side have obvious difference when unbalance loading,the stiffening beam and the cable system show obvious transverse torsion state,and the bridge tower is in the bending and torsion state.In the temperature effect,the main cable elevation is negatively correlated with the temperature.Under the effect of transverse static wind load,the maximum transverse displacement occurs in the span.In the extreme state,the lateral displacement is still less than the limit value,and the structural safety meets the requirements.5.Based on the dynamic characteristics of the suspension bridge,a numerical simulation method is used to analyze the dynamic characteristics of the bridge.The influence of main cable,hanger rod,stiffening girder,cable tower stiffness and constant load change on the dynamic characteristics of the bridge is studied.This paper studied the influence of the central buckle,transverse wind support and other components on the dynamic characteristics of the bridge.The results show that the rail-road suspension bridge should be analyzed in accordance with the flexible structure,and the overall rigidity of the rail-road suspension bridge is larger than that of the ordinary highway suspension bridge.The stiffness of the main components mainly affects the vibration characteristics of the main components.The central buckle and transverse wind support are effective for improving the structural vibration characteristics and improving the overall stiffness of the structure.6.Based on the classical theory of single wheel bridge model,the dynamic response analysis model of the bridge is established.The dynamic response of the bridge under the designed moving load is analyzed,and the influence of load speed and quality on the structure is studied.The results show that the dynamic response is the most obvious.Under the action of moving load,the maximum vertical displacement occurs near a quarter of main span;When the speed is less than the critical speed,the dynamic response of the structure increases with the increase of the speed.When the speed exceeds the critical speed,the dynamic response of the structure decreases with the increase of the speed.The structure has the vehicle bridge resonance point with the speed control in the speed range[60km/h,100km/h].The dynamic response of structure increases with the increase of mobile load.