Research On Reducing Human-induced Vibrations And Seismic Effects In Pedestrian Steel-concrete Arch Bridges

In recent years,pedestrian bridges are commonly designed using the steel tube concrete arch bridge form.The acceleration generated by dense pedestrian traffic is difficult to meet regulatory requirements,making it necessary to suppress vibration.This type of bridge is susceptible to significant longitudinal displacement during earthquakes,which could damage the bridge deck and endanger pedestrians.It is critical to reduce earthquake response in these bridges.This article focuses on controlling vibration response due to pedestrian traffic and seismic response in pedestrian steel tube concrete arch bridges.The following work was primarily conducted:1.Analysis of Pedestrian-Induced Vibration and Comfort Evaluation in Steel Tube Concrete Arch Bridges for Pedestrian UseA finite element model of the pedestrian steel tube concrete arch bridge was established to calculate the acceleration response values for different pedestrian traffic levels and analyze pedestrian comfort.The results showed that the comfort level reached the unacceptable range of CL4 under traffic levels TC4(pedestrian density of1.0 person/m2)and TC5(pedestrian density of 1.5 persons/m2).Considering safety and comfort factors,it is necessary to suppress pedestrian-induced vibration.2.Suppression of Pedestrian-Induced Vibration in Steel Tube Concrete Arch Bridges for Pedestrian Use.Based on experience,suitable MTMD parameters were selected for trial calculations,and analysis revealed that it could effectively suppress pedestrian-induced vibration.The parameters for MTMD were further optimized,and it was found that a higher mass ratio results in better vibration reduction.Moreover,a relationship was established between the bandwidth and the additional damping ratio.The optimized MTMD was capable of controlling acceleration to a comfort level above moderate,demonstrating its excellent performance.3.Static and Dynamic Load Testing of Steel Tube Concrete Arch Bridges for Pedestrian Use.The structure was subjected to static and dynamic load testing to verify that its stiffness and strength meet design requirements,and that its ability to recover from deformation and cable force are normal.The testing concluded that the bridge’s bearing capacity meets code requirements.Subsequently,dynamic load testing was performed,and the peak acceleration response values obtained were consistent with the finite element analysis results,verifying that MTMD can achieve a vibration reduction effect of over 80%,which agrees well with the simulation results.4.Research on Seismic Reduction Technology of Pedestrian Steel Pipe Concrete Arch Bridge with Viscous Damping DevicesThe seismic performance of a case bridge under earthquake loads was discussed.The time history analysis method was used to calculate and analyze the seismic response of the structure with three different restraint systems,including a fixed support system with a viscous damping device of damping coefficient C = 190 k N/(m/s)and damping index α=0.1,and a viscous damping device of damping coefficient C = 450 k N/(m/s)and damping index α=0.3.The calculation results showed that both types of damping devices had a good seismic reduction performance,with the device having a slightly better effect on reducing the bending moment response of the structure than the shear force response.With regard to the damping device itself,the seismic deformation of the device with damping coefficient C = 190 k N/(m/s)and damping index α=0.1 was generally larger than that of the device with damping coefficient C = 450 k N/(m/s)and damping index α=0.3.5.Full-Scale Test of Viscous Damping DevicesFull-scale tests were conducted on two types of damping devices with damping coefficient C = 190 k N/(m/s)and damping index α=0.1,and damping coefficient C =450 k N/(m/s)and damping index α=0.3,respectively.The test results showed that the deviation between the measured test force and the theoretical force for both devices was within ±15%,which met the requirements of relevant technical regulations and could be used for seismic reduction design of actual bridges.By combining finite element simulation analysis with experimental methods,this article conducts a technical study on vibration control and seismic reduction of a pedestrian steel pipe concrete arch bridge.It is concluded that the MTMD has a significant vibration control effect,and the viscous damping device has a significant seismic reduction effect.Reasonable parameters for actual engineering vibration control and seismic reduction work are provided for the case bridge.This research can provide theoretical and experimental reference for vibration control and seismic reduction work of similar bridges.