Wind Vibration Response Analysis And Fatigue Life Prediction Of Cantilevered Traffic Signal Structures

Traffic signals as an important traffic facility to guide the orderly operation of vehicles on the road and maintain road traffic safety,the importance of the safety and stability of its overall structure for traffic is self-evident.Cantilever traffic signal structure is a class of cantilevered flexible structure,because of its high height and large aspect ratio,wind load often becomes the main load to control its structural design.By analyzing the wind vibration response of the structure and its fatigue life,is of great practical significance for the reasonable design of the structure and thus the effective maintenance of road traffic safety.Based on this,this thesis takes an actual large-span cantilever traffic signal structure as the engineering background,establishes a finite element model that meets the characteristics of the actual structure,and conducts a numerical wind tunnel simulation analysis.The coupled vibration mechanism of the structure in the wind field is studied and the fatigue life of the structure is predicted.The main research contents and conclusions of this thesis are as follows.(1)A finite element model of the full-size cantilever traffic signal structure is established,the dynamics of the structure are analyzed and the most unfavorable location of the stress of the structure under wind loads is discussed.The results show that the most unfavorable location of the structure under combined wind and gravity loads is at the cantilever-vertical pole connection.Under dynamic loading,fatigue damage due to stress cycling is more likely to occur here.(2)A numerical wind tunnel applicable to the cantilever traffic signal structure is established to summarize the vibration characteristics of the structure by analyzing the time domain response of the structure under different incoming flows.The results show that the structure generates large cross-wind vibrations at wind angles of 90° and 270°.The displacement response of the structure is positively correlated with the wind speed at a 90° wind angle,and the response is consistent with the phenomenon of galloping.At a wind speed of about 5 m/s at a 270° wind angle,the structure undergoes vortex vibration.Due to the different effective wind areas of the structure,the magnitude of its along-wind response also has some differences.(3)Wind vibration response analysis was performed on traffic signal.structures with different cantilever lengths to obtain the vibration characteristics of different size-types of structures.Since the cross-wind vibration response of the structure is obvious in some cases,a preliminary investigation of its cross-wind vibration suppression measures is required.The results show that the suppression effect of setting the damping plate on the structural vibration is reflected in the wind speed greater than 6 m/s at 90° wind angle;at 270° wind angle,the suppression effect of the damping plate is reflected in the wind speed range of 3 m/s～8 m/s.The effective wind area of the structure as a whole is increased due to the setting of the damping plate in the alongwind vibration response,and the overall force of the structure will be improved accordingly.(4)Based on the cumulative fatigue damage theory,the fatigue life of the structure is predicted.Due to the wind loading,the structure will continuously experience stress cycles at the danger points.The results show that the fatigue life of the large-span cantilever traffic signal structure at a certain location is predicted to be 17.77 years when the Weibull distribution function is considered.