Human-induced Vibration Serviceability Research Of Flexible Stair Based On Biodynamic Model

In recent years, with a large number of applications of the high-strength materials and continuous improvement of construction techniques, it gives designers greater scope for imagination and creative space, so the number of long-span flexible staircase is increasing. But long-span flexible staircase have less gravity, so it leads to the lower natural frequency which is closer to the pacing rate of a pedestrian. So it is easier to lead to resonance and larger response. It at least will affect the normal use,and worst of all will lead to safety accidents. So the serviceability should be paid enough attention to these staircase.At present, the methods, which are used in the study of the structure vibration of the floor and bridge, are followed to use in the study of the human induced vibration of stair. However, due to the characteristic of pacing rate, step, bending of knee of pedestrians when walking on such floor and other plate structure, is different with the characteristic in the spatial structure of the stair. So, the human-induced excitation is great different among these two kinds of structures. The dynamic interaction between pedestrian and the structure can not be ignored when people walk on the stair,especially for long-span flexible staircase. At present, there is a lack of research on the dynamic interaction between human and structure on stair. So it is necessary to study the human-induced excitation and dynamic interaction between human and stair structure.In this paper, the human induced vibration and reduction control problems are studied in the following aspects:(1) The research of human-induced excitation on stair. The walking acceleration is measured and recorded by the new MEMS AH100 B triaxial accelerometer when walking on stair. The lots of acceleration signals are analyzed using MATLAB. Then fourier series function is established, and the harmonic dynamic load factor, phase and frequency are counted.(2) The research of biodynamic model on stair. A single degree of freedom system including m, c, k for the pedestrian on the stair is established. This model is equivalent to a nonlinear equation group at last. The input parameters can be obtained through test. m, c, k are obtained by solving the equivalent in MATLAB. Then three fitting curves on the processed data are carried out. And the calculating formula ofthree parameters are obtained.(3) Vibration analysis of stair. A finite element model of beam-column steel staircase of hall of a Science and Technology Museum is established in ANSYS,different kinds of excitation are employed to simulate the vibration of the stair,include the excitation on floor and excitation on stair which is studied by foreigners.And several kinds of evaluation methods are used to evaluate the serviceability of stair. Then the measurement of thickening treads of stair is put forward to reduce the vibration. In a addition, a finite element model of a 360-degree spiral steel staircase is built, two kinds of excitation and two kinds of biodynamic models are employed to analysis the dynamic response of the stair. Then Three different kinds of optimized models of TMD were applied to control the vibration of the stair. And the effects of vibrating reduction are compared.