Experimental Testing And Theoretical Modelling Of The Vertical Interaction Of Human-structure System

With the development of construction techniques, structural natural frequencies become lower and lower which make the structural vibration more likely to be excited by the crowd-induced loads and thus cause the issues of comfort and even safety. Therefore, the research of human-structure interaction system tends to be increasingly sign-ificant. With deeper understanding of the crowd-induced load, the modelling of human body has been evolved from a simplified mass to a dynamic system which is a breakthrough achievement in the reseach of human-structure system. However, the model of human body used in engineering could not fully reflect the impact on the structure caused by the human body. Besides, the domestic theorrtical and experimental research on human-structure interaction system are insufficient. Therefore, the three degree of freedom(3DOF) model about mass-spring-damper is proposed in this thesis to study thehuman-structure interaction system. The main contents of this disertation are as follows:(1) The 3DOF human-structure interaction system theoretical model was constructed. In the 3DOF model, the human body was modelled as two degree of freedom(2DOF) which includes two ways of DOF connection, namely two DOF in series and two DOF in parallel. When it acts on, 3DOF human-structure system model is therefore obtained by connecting the 2DOF human-body model and the single degree of freedom(SDOF) structure model. Considering the high damping capacity of human body, the forced vibration equations of 3DOF human-structure system were derived and the acceleration response function of the structure was obtained. Through analysising of the resonant frequency of the system and comparing the numerical simulation results with those existing ones, the formula derivation of the theoretical model and the according MATLAB program were validated. Meanwhile, simulation of the existing experimental results shows: When using the human body parameters from Griffin’s model, the 3DOF human-structure model of which the human body is modelled as 2DOF connected in series can basically reflect the dynamic characteristics of human-structure system, while the one of which the human body is modelled in parallel does not work properly.(2) The vertical vibration characteristics of human-structure system were studied experimentally. Circular steel plate and spring were set up to simulate a SDOF structural model in experiment. Three test conditions were considered to measure the respective natural frequencies: single person standing on the model, single person standing on the model with both legs bent, group of people standing on the model. The increase of natural frequencies when single person stands naturally on the test plate indicates that human body can not be considered as additional mass attached on the structure which will only lower the structural frequencies. When the frequency of SDOF structural model is lower than 11.50 Hz, both cases, the body standing naturally and standing with legs bent on the plate, show two resonance frequencies: one is greater than the natural frequency of the structure, the other is less than it. Compared to single person standing with legs bent, the condition of legs bent provides more damping to the structure. Finally, it is found that the varied weight of standing human body has little effect on the resonant frequency of the system.(3) The 3DOF theoretical model is used to simulate the test results. Comparing the simulation results from the 3DOF theoretical model with the experimental resonance frequencies of the human-body systems(obtained when the body standing still and standing with legs bent on the tested plate), it is found that the human body model parameters by Griffin can not be applied directly to the human-structure interaction system in practical engineering structures. The simplex method was adopted to optimize the model parameters of the 3DOF model in order to match the test results(3DOF model are composed either by 2DOF human body model in series or 2DOF human body model in parallel). It is found that the 3DOF model in series with optimizated parameters can simulate the test results with higher accuracy.