Vertical Vibration Serviceability Analysis Of A Large-span Floor Gymnasium

With the support of new materials and technics, the modern construction technology which breaks through the traditional design limitation, is applied to more and more large-span structures. The increasing span of the floor influence structure mass and stiffness that directly decrease the nature frequency, so that the structure becomes more flexible and easily causing vibration problems. Because that problem directly affect the function of building in serviceability limit state, the concept of human comfort based on dynamic analysis was proposed to consider the influence of pedestrian dynamic load.The serviceability design of rythmic activities floor is not adopted by domestic design code, and the calculation nature frequence of the large-span floor does not satisfied the minimum frequence of 6Hz according to foreign standard. According to the research of human induced load, cases are established to anaiysis a large-span floor natatorium in a university; walking load is assigned to the first and second floor, and the time-history analysis is used to evaluate serviceability of the large-span floor. The purpose of this article is to analysis the vibration performance of the floor under current design scheme, and evaluate the vibration lever under normal service condition. This article achieve following conclusions:1 Domentic building codes has little concren to the rythmic activity serviceability design, and only publish a frequecne-accerlation standard for office and residential buildings refer to foreign design code. This article compare multiple foreign standards and adopt the frequence weighting based RMS acceleration standard from ISO code. The load cases build upon walking, running, jumping and other load which would appears in a high frequence in serviceability stage are established according to the movement appearing on gymnasium floor.2 This article compare the time-history result of the large-span floor under single person, multiple person and group size person load cases. The conclution shows that walking could not lead to vibration problems while jumping and running could induce serviceability problem under normal activities. The coordinate factor affected crowd load under 25 people is easily induce vibration problem. According to the analysis result, jumping and running should be the main load cases for gymnasium vibration serviceability research, and crowd load model must be applied to analysis.3 Time history signal could not display the characteristics of the floor, to analysis the dynamic characteristics of large-span floor under the occupants loads, fast fourier transform is used to change acceleration time history response to frequency domain. Acceleration spectrum reveal that major vibration serviceability problem is induced by resonance phenomenon when the load frequency and multiple frequency is close to the floor natural frequency, and does not present the higher harmornic component effect. Floor vibration problems are related to the nature frequency refer to domestic and foreign projects. So that the specific analysis of a floor is necessary to avoid human induced vibration problem.