An Improved Design Of Plate Eddy Current TMD And Its Application In Footbridge Vibration Abatement

With the widening of new municipal roads,the span of footbridge is enlarged.In addition,the use of light and high strength building materials in the construction of footbridge and people’s aesthetic requirements on the shape of footbridge,the footbridge has the characteristics of large span,light shape and low damping.The long-span footbridge has a low base frequency,and when it falls into the frequency range of pedestrian load,it is easy to cause the man-bridge resonance phenomenon.If pedestrians number exceeds a certain value,the resonance that makes the pedestrian bridge across the amplitude of vibration will appear uncomfortable and even psychological panic,cause the footbridge vibration comfort problems,therefore,for all the large span footbridge vibration problem is analyzed,and potentially comfort problem of bridge control measures has the necessity and value.Eddy current TMD is widely used in aerospace,vehicle braking and other fields due to its advantages of no mechanical wear,stiffness and damping separation,simple maintenance and so on.With the commercialization of the new generation of permanent magnets represented by Nd Fe B,it is possible for eddy current TMD to be applied in the field of seismic and vibration reduction in civil engineering,and it has a broad prospect.Combined with the demand of footbridge vibration reduction,an eddy current TMD is improved and designed to verify its effectiveness,which appears to have practicability and certain scientific research value.This paper takes the pedestrian bridge vibration reduction as the goal,and takes the eddy current TMD as the vibration reduction measure,and studies the application of a plate type eddy current TMD in the pedestrian bridge.The main work is as follows:1 、 Based on the deterministic pedestrian load,the single-person bridge-bridge vibration equation,crowd-bridge vibration equation and crowd-bridge-TMD coupling vibration equation are constructed respectively.2、The damping principle of TMD is described,and an improved design of eddy current TMD is proposed.And through the finite element simulation analysis of the conductor plate thickness,thickness of permanent magnets and the air gap magnetic induction intensity on the surface of a conductor plate respectively,the influence of the magnetic induction intensity on the surface of the conductor plate and permanent magnet thickness were positively correlated,and negatively correlated with conductor plate thickness,and negatively correlated with the air gap,on the basis of analyzing the three parameters on the right value of each parameter is given.3、Taking a pedestrian bridge project in a certain place as the background,a finite element modeling was constructed,and five different pedestrian load conditions were established with two pedestrian excitation models to conduct human-induced vibration analysis,and it was found that the peak acceleration of the operating conditions exceeded the limit of ISO2631.It is required that after adopting the eddy current TMD vibration reduction,all traveling loads meet the requirements of ISO2631,and the eddy current TMD vibration reduction efficiency exceeds80%.4、Taking the pedestrian bridge model as the test object,and the plate-type eddy current TMD prototype as the vibration reduction measure,the effectiveness of the eddy current TMD prototype on the pedestrian bridge vibration reduction was tested through experiments,and the fast,medium and slow running conditions were obtained.The average damping efficiency of eddy current TMD reaches 70.20%,44.70% and 29.53% respectively.