Research On Human-induced Vibration And TMD Damping Of Long-span Pedestrian Suspension Bridge

The pedestrian suspension bridge in tourist attractions is accompanied by the use of high-strength new materials,resulting in continuous aesthetics and flexibility of the structure.Therefore,self-oscillation frequency and damping of the suspension bridge are gradually decreased.Under the action of humaninduced load,excessive vibration of pedestrian suspension bridge is easy to occur,which makes people feel uncomfortable psychologically.It is necessary to carry out pedestrian load vibration research on pedestrian suspension bridges.In this paper,a large-span pedestrian suspension bridge with a span of 250 m is taken as the engineering background.After determining the cable force of the bridge by iterative method,the dynamic characteristics and influencing parameters are studied in depth,and the human-induced vibration time history response analysis and comfort evaluation are carried out.Finally,Tuned Mass Damper(TMD)is used for vibration reduction design.The main findings are as below:(1)ANSYS software was used to build a suitable 3D finite model based on the background,along with using iterative method to determine the cable force,analysing its natural vibration characteristics.In addition to,the influence of two parameters,the main cable vector-to-span ratio and the stiffness of the stiffened beam,on the dynamic characteristics of the structure is investigated.The results shows that the bridge basis frequency growth with decreases of cable curve risespan ratio,along with the augment of stiffening girder stiffness increased.(2)The differences and applicability of the codes in various countries are analyzed on the basis of summarizing and comparing the current design codes of footbridges at domestic and international,by comprehensive comparison of the fundamental frequency requirements,pedestrian load models,comfort index levels and evaluation methods.The German EN03 code is selected to study the time-history response of human-induced vibration and evaluate the comfort level of the background engineering.(3)Different crowd load conditions are selected based on the German pedestrian load model.On the one hand,the time history response analysis of vertical and transverse human-induced vibration is carried out based on the background project.On the other hand,comfort evaluation is implemented through selecting 1/4 and 1/2 of main beam as the control section.The results shows that the comfort evaluation of the 4th mode is “very comfortable”,which meets the requirements of pedestrian comfort and does not require vibration damping design;the comfort evaluation of the 11 th mode and the 37 th mode are both “uncomfortable”,which cannot meet the requirements of pedestrian comfort and therefore require vibration damping design.(4)Based on the vibration reduction principle of Tuned Mass Damper(TMD),the TMD vibration reduction scheme is designed.The vertical and lateral acceleration time-history responses before and after the installation of TMD are compared,and the comfort degree is evaluated.Studies are conducted for the installation location and design parameters of the TMD.The results shows that the TMD can significantly reduce the human-induced vibration response;The larger the mass ratio of the TMD,the better the vibration reduction effect of the structure installed at the maximum vibration displacement.For large span suspension bridge of footbridge vibration and vibration reduction research,to provide some reference for the design and structure of this kind of suspension bridge in the future.