Analysis Of Mechanical Characteristics And Traveling Wave Effect Of Long-span Suspension Bridge

Since the reform and opening up,China’s economic level,scientific and technological level and comprehensive national strength have been continuously improved,and the infrastructure construction has ushered in an earth shaking change.In 2019,Wuhan yangsigang Yangtze River Bridge,the second largest bridge in the world,was built.China has entered a new period of suspension bridge construction.The span of the suspension bridge is becoming larger and larger,the bridge site is becoming more and more complex,and the bridge is also facing more complex stress conditions.Therefore,we need to conduct more in-depth research on the bridge structure.Based on the relevant research at home and abroad,this paper takes a suspension bridge with a main span of 808m as the engineering background,and the main work is as follows:(1)According to the principle of finite element,Midas civil is used to build the model of the whole bridge,analyze the status of the bridge and live load,and clarify the mechanical characteristics of the whole bridge.The results show that the stress of the main tower and the main cable sling system is reasonable,and the strength and rigidity meet the requirements of the code.(2)The parameters of suspension bridge are analyzed.The effects of rise span ratio,axial stiffness of main cable and bending stiffness of main girder on structural stress are studied.Reducing the rise span ratio is beneficial to increase the stiffness of the structure,but the internal force of the main cable and the bending moment at the bottom of the tower increase.When the rigidity of the main cable is increased,only the internal force of the main cable is increased,and the other internal forces and displacements are reduced.With the increase of flexural rigidity of stiffened beam,the influence of main tower and main cable is very small,which mainly affects the mid span bending moment and deflection of main beam.(3)Based on the analysis of the natural vibration characteristics of the suspension bridge,the influences of the rise span ratio,the main cable stiffness,the main beam bending stiffness and the main tower stiffness on the dynamic characteristics of the suspension bridge are studied.When the rise span ratio decreases,the vibration frequency of most modes increases,and the vibration frequency of the main tower decreases all the time.When the rigidity of the main cable increases,the frequency of the first-order symmetrical vertical bending increases obviously.The frequency of transverse and vertical bending of the main beam increases obviously with the increase of the rigidity of the main beam.The stiffness change of bridge tower only has a great influence on its vibration frequency.(4)The results show that the response law of the structure under the earthquake action of E1 and E2 is basically the same,but the internal force and displacement response under the earthquake action of E2 is generally larger than that under the earthquake action of E1,only the axial force of the main tower increases slightly.(5)The results show that the uniform excitation underestimates the influence of earthquake on the structure.When considering the effect of apparent wave velocity,the results show that the internal force and displacement of the structure change obviously at low apparent wave velocity,especially the axial force,shear force and bending moment at the bottom of the tower vibrate,the amplitude of change starts to decrease at medium and high apparent wave velocity,and the peak value of displacement and internal force response tends to be stable at high apparent wave velocity,which is close to the result of consistent input.