Frequency Domain Analysis Of Large-span Structural Response Under Random Crowd Loads

Modern new building gradually develop to be large span, soft, economic and aesthetic. Under traditional design, the bearing capacity and some static properties of such structures usually meet the design requirements, but its dynamic performance, especially excessive vibration under crowd excitation, may become a key issue restricting its application and development. At present, the number of large-span structures gradually increased, and there has happened some structural damage or excessive vibration phenomena caused by crowd load, so more and more scholars began to study the impact on the structure of pedestrian load. There usually be two ways to solve the structural response:time domain method and frequency domain method. Previous studies mostly used time-domain method to study the influence of crowd load to structure, which assumes crowd load model (generally use Fourier series model) and using the finite element software to apply crowd load model in order to obtain the structural response. But the actual pedestrian load is not necessarily strictly periodic function, whose frequency is not only distributed in individual discrete points but distributed in a certain frequency range. It is not consistent with the actual situation when using strict form of periodic functions as pedestrian load model to solve the structural response, however, using frequency-domain method which first gets power spectrum then solve the structural response can be good to avoid this problem, and the obtained mean square response can just be used to evaluate the comfort structure. This article reference wind vibration frequency domain algorithm for solving large-span structural response under stochastic crowd loads. In this paper, the following research work has done.First, respectively giving all kinds of single load models and crowd load models. Among them, the single load model consist of deterministic load models, such as the Fourier series load model, sinusoidal load model, IABSE model; there are also single load model based on probability analysis. About crowd load model, this paper mainly describes equivalent synchronization number method, fixed multiplayer walking force method and moving multiplayer walking force method. In this paper, first two methods are used, the first two methods are simple and useful.Secondly, the frequency domain algorithm solving structural response under crowd loads is detailed described, which firstly gets power spectral of structural response then takes integral operation to obtain mean-square value. Then, citing specific examples to verify the theoretical algorithms and using spatial correlation coefficient to measure the degree of correlation among the crowd. On the basis of the obtained mean square value of response, confidence intervals of structural response with different ensure coefficient can be solved.Finally, MTMD vibration control method used in large span structures under pedestrians is introduced. And an actual project example using MTMD vibration analysis is also described. Through finite element analysis and practical tests before and after damping, theory values and measured values of structural response are compared, then this paper get that the MTMD damping solution is reasonable.