Research On Human-Induced Vibration Comfort And Vibration Reduction Of Special-Shaped Pedestrian Bridges

With the development of our country’s social and economic,many pedestrian Bridges have been added to reduce more and more traffic pressure.Most of these pedestrian Bridges are steel structures with large and soft spans,resulting in low fundamental frequency of the structure.When the pedestrian Bridges are in the sensitive frequency range of human-induced vibration,the resonance phenomenon of the human bridge will occur.The vibration and comfort of such pedestrian Bridges have attracted more and more attention from scholars and the society.At present,some studies have been carried out on the comfort level of pedestrian Bridges.With the increasing complexity of the structure of pedestrian Bridges,the research on the comfort level and vibration reduction of special-shaped pedestrian Bridges is still a hot topic.Based on the example of a complex pedestrian bridge project,this thesis systematically studies the pedestrian load model establishment,human-induced vibration calculation method,comfort evaluation,vibration control and other contents.The main work is as follows:(1)Summarizes the research results of scholars from various countries on the pedestrian load,the evaluation method of pedestrian bridge vibration comfort and pedestrian bridge vibration control.Points out the limitations of the method of avoiding sensitive frequencies in the current "Technical Specifications of Urban Pedestrian Overcrossing and Underpass"(CJJ69-95)in practical engineering applications.(2)The characteristics of the foot dynamic load,the pedestrian load model,the pedestrian load model and the comfort evaluation method in 6 foreign pedestrian bridge design codes are studied.The pedestrian load models and comfort evaluation methods in these codes are comprehensively compared,and the similarities and differences between the codes of various countries are summarized.Among them,the German and French codes classify the comfort level,and the crowd load model takes into account the different traffic volumes.It is a relatively advanced code with strong operability when designing footbridges.The International Standard ISO 10137 considers the comfort evaluation index of pedestrians under different motion states,and is also a relatively comprehensive specification.(3)Taking an actual project as an example,the finite element model of pedestrian bridge was established based on Midas Civil software,and the natural vibration mode of the pedestrian bridge is analyzed.Combined with foreign codes and my country’s "Technical Specifications of Urban Pedestrian Overcrossing and Underpass(Draft for Comment)",an analysis of the human-induced vibration response was performed and the comfort of the pedestrian bridge was evaluated.(4)The vibration control measures of the pedestrian overpass are studied.By analyzing the applicability,advantages and disadvantages of three different vibration reduction schemes,the method of adding a tuned mass damper is used to control the vertical vibration of the pedestrian overpass.According to the parameter optimization formula,the TMD and MTMD system of the pedestrian bridge are designed,and the human-induced vibration response analysis is carried out on the pedestrian bridge after the additional vibration reduction device.From the analysis results,it can be seen that the pedestrian bridge meets the optimal comfort level.