The Dynamic Performance And Vibration Experimental Research With People Of The Pedestrian Bridge

Pedestrians can often feel the obvious vibration after some pedestrian bridges,which is easy to arouse people’s psychological panic,and bring discomfort to pedestrians.After the excessive vibration of The London Millennium Footbridge in 2000,although foreign scholars have carried out relevant research on this issue,but it has not really attracted people’s attention.,and the results are not completely suitable for the national conditions of our country,and the domestic researches are less and less.Therefore,it is necessary and urgent to carry out the related research.In this paper,the author first summarize the experience of predecessors,and then use the design of the pedestrian continuous walking excitation test device to measure and analyze the vertical component pace of the 20 testers.Then,the 941B type ultra low frequency vibration measuring instrument and the Beijing spectrum acquisition instrument were used to test the east gate pedestrian bridge of Xi’an university of technology under the conditions of environmental excitation,single walking,standing step and crowd walking,Obtained the dynamic characteristics of the bridge structure,which can provide the necessary information for the subsequent reinforcement and reconstruction of the structure.Finally,based on the MIDAS Civil platform,the finite element model of the bridge is established,and the vibration response of the pedestrian bridge is simulated by using the measured force curve.Specific contents and conclusions are as follows:1.The design of pedestrian walking biped testing device of continuous stimulation on vertical walking load were measured.The collected data were analyzed and summarized,and each test step vertical superimposed stress curve drawing,simulation of the complete process of continuous walking pedestrians.Based on the comparison of the vertical force curves of each walking are obtained.2.Based on ambient excitation(pulse,traffic,wind etc.)under the deck acceleration response spectrum analysis,the structural dynamic characteristics of the bridge,the bridge structure to identify the natural frequency,vibration mode,and the damping ratio of the structure is obtained by fitting the wave attenuation value and the free attenuation method.The bridge field test data can accumulate technical data for the safety evaluation of the project after the day,but also provides a reference for similar engineering design.The test data shows that the frequency structure clearly,the first vertical frequency of 3.467Hz to meet the requirements of Technical Specifications of Urban Pedestrian Overcrossing and Underpass(CJJ69-95),but it is close to the minimum requirements of 3Hz.The half power bandwidth method is used to calculate the damping ratio of the bridge.The results are as follows:1.64%.3.Put forward the experimental scheme of the man standing resonance of the pedestrian bridge in the east gate of Xi’an University of technology.The test personnel in accordance with the fundamental frequency of the bridge marking time,recording the vibration waveform curve bridge complete,the maximum acceleration of the bridge marking time under the condition of value,to analyze the collected data to get the fundamental frequency of bridge;Decrease in vibration waveform curve,a numerical intercept vibration waveform is larger,the waveform peak and trough values are fitted respectively,found relatively concentrated trend lines around the data points show that the attenuation peak value between high fitting degree;Then,the damping ratio of the bridge structure is calculated by using the free decay method,and the calculated results are as follows:7 of the maximum values of the amplitude of the bridge are arbitrarily selected.The results are as follows:1.17%.4.The dynamic response of the bridge is analyzed under different working conditions,and the dynamic response of the bridge is analyzed under different frequencies,the number of pedestrians and the form of interaction.The test results show that the frequency of the bridge measured at different load conditions is about 3.4Hz,and the vibration mode is mainly based on the first order.When the bridge pedestrian bridge in accordance with the vertical frequency running or stagnant condition,bridge vertical acceleration maximum reached 1499.72mm/s~2,far greater than the other conditions,also greatly exceeded the body feel comfort requirements,then reach the footbridge resonance state.5.Based on the MIDAS Civil platform,the finite element modeling and analysis are carried out to obtain the dynamic characteristics of the bridge,and the measured results were compared to that bridge under ambient excitation,the bridge vertical frequency difference of not more than 10%,more consistent.The difference between the transverse frequency values is larger than that of the vertical,and the difference of the first order frequency is 29.06%.Then,use a pedestrian pace force curve in the second chapter through pedestrian force measurement test,calculation and analysis of the pedestrian bridge in the single(walking and running)and pedestrian response under load,and the measured results also were compared,analyzed the difference between the two reasons.