Human-induced Vibration And Vibration Control Of Curved Footbridge With Single Cable Surface

Modern footbridges tend to be long-span and gentle,resulting in low frequency and small overall stiffness.Under the action of crowd load,people and Bridges are prone to resonance phenomenon,which makes pedestrians feel uncomfortable.Due to manufacturing error of bridge structures,construction error and the finite element model when modeling the presence of large amounts of simplified assumption,etc.,will make the calculated results of finite element model and the actual situation of the bridge there is a certain difference,so the finite element model should be modified before the human-induced vibration analysis and comfort evaluation of footbridge to improve the reliability of subsequent analysis results.In this paper,finite element model modification,local force,human-induced vibration response,pedestrian comfort evaluation and vibration reduction control are studied based on single cable curved footbridge.The main work is as follows:(1)According to the design drawings of the footbridge,MIDAS/Civil software is used to establish the initial finite element model.Based on the field measured data,the finite element model is modified based on response surface method.The results show that the error of the modified finite element model is significantly lower than that before modification and is in good agreement with the measured data.(2)Combined with the stress characteristics of the footbridge,two key parts are selected and analyzed locally by direct modeling method using MIDAS/Fea software.The analysis results show that the stress concentration is obvious near the welding place between the main beam and the key platform and the inner ring of the lifting lug at the anchor junction of the most right cable,and the maximum stress meets the strength design requirements of Q345 steel.(3)The provisions of pedestrian load model and comfort evaluation in five codes are compared and studied.German code EN03 with stronger applicability is selected to provide theoretical guidance for subsequent comfort evaluation.Considering the crowd stopping effect,MIDAS/Civil software is used to analyze the dynamic characteristics of the footbridge,and the human-induced vibration analysis and comfort evaluation are carried out in combination with The German standard EN03.The results show that the vertical frequencies of the 5th and 6th modes of the bridge are between the human-induced vibration sensitive frequencies before and after considering the crowd stopping effect,and the vertical human-induced vibration acceleration response should be analyzed.In the subsequent comfort calculation,the comfort level of vertical human-induced vibration of the fifth and sixth modes is "unacceptable".(4)Three common vibration reduction methods are analyzed,and the harmonic mass damper(TMD)is selected to control the vibration response of the structure.Based on the TMD optimal parameter design method,three vibration control schemes are designed for footbridge under the condition that the total mass of order 5 and 6 TMD is not changed.The results show that the comfort level of human-induced vibration of footbridge corresponding to the first scheme using single TMD is "medium".The comfort level of human-induced vibration of footbridge corresponding to scheme 2 and 3 using three TMDS for vibration reduction control is "best",and the vibration reduction effect is better than scheme 1.