Simulation And Vibration Response Analysis Of Stochastic Crowd Load In Large-span Floor Structure

The rapid development of construction technology and the development of new building materials have made large-span floors widely used in complex space structure.Compared with conventional structure,this type of system is lighter,more flexible,and less damped,which cause its vulnerabilities to vibration comfort problems under the excitation of vertical loads,especially pedestrian loads.The current research on crowd load is not perfect enough for its characteristic of higher independence and randomness in the process of walking.Therefore,it is necessary to study and analyze the vibration response of large-span floor structures under random pedestrian loads,and provide reliable evaluation methods and design law for the comfort evaluation of large-span structures.This article starts with the single-person walking load test,and establishes a single-person continuous walking load model that conforms to the characteristics of the Chinese person.The vibration response of a structure under random crowd loading was studied and analyzed with the established load model and the test data of an actual waiting hall of the high-speed railway station.The main research work and results of the vibration response of the structure under random load are as follows:1.Using the direct measurement method,a single-person walking load test of 1,040people was carried out using force plates.Through the analysis of the single-step load curve collected in the experiment,the parameter distribution law and the relationship are obtained between the parameters such as the step frequency,stride length,the dynamic load factor and walking speed of the tester during the walking process.Based on the single-step load test data,the single-person continuous walking load curve was obtained by expanding according to the landing time point of each step and the single-step expanded continuous walking load model was proposed.Considering the randomness of the walking process,the parameters of the random single-person continuous walking were given.2.Based on the classical thin plate bending theory and structural dynamics,the calculation method of forced vibration of large-span floor structures and the analysis of dynamic response in the time domain are summarized.Also,the calculation formula for the vibration response of rectangular thin plate under the vertical concentrated force is derived.The acceleration of the floor under the walking force of the crowd is obtained.Improved the traditional social force model,constructed a random crowd load model in line with the characteristics of Chinese walking,and programmed to construct a stochastic crowd program simulation system based on social force model.3.Taking the large-span floor structure of the waiting hall of a high-speed railway station as an example,the acceleration response of the structure under random crowd load is analyzed.The Monte Carlo method is used to calculate,and the results show that the Xiong’an station waiting hall floor slab bears the maximum response under the human-induced excitation with the frequency of 2.0 Hz.The calculation method proposed in this study under the deterministic pedestrian load is within 5%of the difference between the numerical result and the finite element simulation result.The human-induced vibration response of the floor slab in the ticket gate area was calculated by simulating the working condition of passengers walking randomly during the ticket checking process in Xi’an North Station.After comparing with the test data,the difference between the calculated value and the measured value is about 15%,which indicates that the model in this paper has a certain degree of reliability in calculating the random walking of the crowd.4.Based on the random single-person walking curves generated with Monte Carlo method,the 10s acceleration RMS value of the 30m span floor slab in the range of 0～10Hz is calculated,and the standard response spectrum is given.The response spectrum parameters under the random pedestrian loads and under different floor span conditions are normalized,and detailed process for the response spectrum of floor vibration acceleration was proposed,which can be used to evaluate the vertical vibration response of floor slabs induced by a crowd.5.Taking the large-span floor structure of the new exhibition hall of Nanjing Art Museum as an engineering case,the analysis of the human-induced vibration response of the structure under different loading cases are carried out.The calculation results show that the vibration comfort of some areas exceeds the specification limit,and the maximum vertical acceleration reaches 255mm/s~2.Based on the results,the energy dissipation and vibration reduction plan was determined,and a total of 21 sets of TMD(Tuned Mass Damper)devices were arranged.The on-site vibration test was carried out on the museum,and the results show that the measured response data are small compared to the FEM software calculated values,while the response spectrum values at 95%guarantee rate and 75%guarantee rate can cover the measured acceleration response well.