Research On Modal Parameter Identification And Riding Comfort Of The Elevated Bridge

With the economic development and social prosperity,the growth of city size and population has led to that road transport is often in a state of busy work.City viaduct makes full use of the space above the original road,shows three-dimensional transport capacity and improves the level of road service;with the growing number of elevated,it gradually becomes the mainstay of urban transportation capacity.Enlargement of bridge deck width is an effective strategy to solve the increasing traffic pressure,which is also a trend of viaduct,wide viaduct.Compared with ordinary beam bridge,wide viaduct is a kind of wide span bridge structure,whose modal must contain bending and torsion coupled mode.At the same time it brings new challenges to modal identification methods.From the mechanical point of view,the increase of bridge width also makes the special effects of the bridge more apparent,vehicle load of bending and torsion coupling a more prominent role,driving comfort problems that may arise therefrom.For the current urban traffic conditions,the sudden rise in number of private cars make that which is close to the red line of traffic volume worse.Especially in the peak hour of the cities,traffic jams often occur.When one-sided traffic jam condition occurs on the viaduct,traffic-congested side is likely to be impacted by the side of good condition,leading to passengers uncomfortable.Thus,this paper carried out the following work based on the viaduct as the research object:(1)The peak picking method and the stochastic subspace identification method were studied in this paper.The two modal identification methods were based on environmental excitation.The program of the two algorithms is written and verified.With the above two methods,the modal parameters identification of a wide viaduct was carried out.At the same time I established the finite element model of wide viaduct.The accuracy of the simulation model of the bridge was verified by comparison of theoretical modal analysis and testing results from both frequencies and mode shapes.(2)According to the evaluation of human sitting comfort,this paper established the simplified model of the vehicle which takes human-seat structure into account and derived its equations of motion.The separate iterative solution strategy was used based on ANSYS finite element analysis software and executable program written in FORTRAN language to solve dynamic problem.Comparative analysis of the results by the test vehicle ride comfort and numerical simulation verified vehicle-bridge system of dynamic interaction established is feasible and effective in terms of driving comfort.(3)The evaluation methods and indicators of vehicle ride comfort was chosen and two traffic models-congestion and free flow-was established in view of the viaduct traffic condition model.Using validated vehicle-bridge system,this paper discussed many situations that the influence by the driving parameters-lanes,vehicle speed and driving distance-and vehicle structural parameters-damping,stiffness and vehicle weight-and other factors on the waiting vehicle ride comfort when traffic jam occurs on the wide viaduct.