Research On Theory And Algorithms For Vibration Control Of Buildings

Buildings, as a part of the civil structures, are important infrastructure and an integral part of the modern society. Traditionally, these structures were designed to resist static loads. Civil structures are, however, subject to a variety of dynamic loadings, including winds, waves, earthquakes, and traffic. These dynamic loads can cause severe and sustained vibratory motion, which can be detrimental to the structure, its material contents and human occupants. The extent of protection required by these structures may range from reliable operation and occupancy comfort to structural survivability. Improving the buildings'seismic performance and tall building wind-resistance performance is one of the basic measures to reduce dynamic functions damage and strengthen regional security, which is currently an important subject in the civil engineering. Structural vibration control is a new technique domain that relates to many subjects. Structural vibration control can improve the reaction and reduce the harm to the structure available under the dynamical functions such as wind and earthquake etc. It strengthens the anti-vibration and anti-disaster ability of the structure. After decades of development, building structure vibration control has been proven by theory and practice to be an effective means to withstand earthquakes and wind damage. Therefore, it will be a worthwhile and great project to study the reasonable and practicable control measures to protect the building structure against earthquake damage and protect tall building structures against wind vibrations on the basis of understanding the building dynamic response characteristics.With the social progress and scientific development, inhabitants call for a better occupancy vibration environment. Passive vibration control can't satisfy the need and exposes its limitation. Active control becomes a new important way because of its effectiveness and adaptability. However, active vibration control system needs a great sum of power and many actuators, which is hard to be realized in the practice. The basic principles of semi-active vibration control is the same with those of active vibration control, but semi-active control makes use of the relative deformation or relative velocity in structure recycle movements, which needs only a small amount of power to achieve the optimal active control force. Symbolized by fuzzy control,neural network control and genetic algorithm, the intelligent control has become a leading field in the study of structure vibration control. Structure intelligent vibration control is free from accurate model of system and uses intelligent algorithms to determine the relationship between input or output feedback and control gains. Run by little power, the intelligent damper made of intelligent magnetorheological fluid materials can achieve optimal active control force.Focused on the object of building structure, this paper employs modern control theory and intelligent control theory to conduct the theoretical analysis and algorithms for building structure vibration control. Firstly, the paper uses active control methods to reduce the seismic response and explore its key problems against earthquake. Secondly, based on the active control, the research concentrates on semi-active control methods. Thirdly, the paper discusses the application of fuzzy control and genetic algorithm in structural vibration control.In the design of structure seismic response active control system, the paper employs five active control algorithms, such as classical linear quadratic optimal control, linear quadratic Gaussian optimal control, pole assignment control, independent modal space control and sliding mode control, to carry out theoretical analysis and numerical simulation of the linear structure model and provide the basis of semi-active control design.Based on active variable stiffness method, a new active variable stiffness frequency control algorithm for seismic response control is presented in the paper. The time-frequency information of nonlinear and nonstationary earthquake signal processing is identified based on Hilbert-Huang Transform algorithm. Using active variable stiffness device, the stiffness of structures is changed to reduce the response to seismic excitation when the instantaneous frequency is close to the frequency of structures. In order to verify the feasibility and effectiveness of the algorithm, two steel-framed Benchmark models are presented. The effectiveness of the algorithm are thus proved through simulation analysis, and the displacement of the structure is reduced effectively. So it has a promising future in the engineering practice.Based on empirical model decomposition and Hilbert-Huang transform theory, the paper develops a new semi-active variable stiffness tuned mass damper(SAVS-TMD) frequency control algorithm for tall building wind induced vibration control. The new SAVS-TMD system has the distinct advantage as it continuously retunes its frequency due to real time control and is robust to changes in building stiffness and damping. The benchmark building under the discussion is a 76-story 306 meters concrete office tower in Melbourne, Australia. It is shown that the SAVS-TMD can reduce the structure response substantially, when compared with the uncontrolled case, and it can reduce the structure response further when compared with the case of TMD. Additionally, it is shown that SAVS-TMD reduces response even when the building stiffness changes by±15% and it remains robust. It is demonstrated that SAVS-TMD can reduce the response as well as active tuned mass damper (ATMD) at the expense of much less power consumption.By employing the auto-regressive method and weighted amplitude wave superposition improved by using FFT method respectively, the stochastic fluctuating wind field and cross-spectral density function have been simulated by using the Davenport wind speed power spectrums and considering spatial correlation, stationary multivariate stochastic process. The accuracy and the efficiency of the technique have been demonstrated by comparing simulating the wind speed spectrums with the Davenport target spectrums. A76-story 306 meters RC structure of the Second Generation Benchmark Vibration Control for Building is under the research. The numerical results of the dynamic response of the structure under TMD control and LQG control methods are given.Iterative learning control is a more satisfactory control strategy because of its own intelligence, which is able to improve itself constantly in controlling process. So it is gradually becoming an issue of concern. Based on the idea to combine the linear quadratic optimal control and iterative learning control, the paper proposes a new hybrid control strategy which is named linear quadratic iterative learning control to reduce the earthquake response of tall building. The strategy can improve the convergence rate of iterative learning control and improve the effect of control. Secondly, with the research into the fundamental ideas of self-tuning control, fuzzy logic, and iterative learning control (ILC), this paper provides a new type of fuzzy iterative learning control strategy to reduce the seismic response of tall building. It improves the robustness of the iterative learning control. The model of a seismically excited building in the Second Generation Benchmark Vibration control for buildings is studied by using the new hybrid control strategy and fuzzy iterative learning control to calculate the seismic response of the building. The result shows that two new control strategies are able to control the model of Benchmark against earthquake effectively and the control effect is improved to some extent.Fuzzy logic control is one of methods in structural intelligent control. Optimization of fuzzy controller, which is based on genetic algorithm, takes advantage of powerful optimization capability of GA and avoids the weakness of ordinary FLC designing which control rules and membership functions of FLC are chosen by expert experiences. It will facilitate the system fuzzy control and achieve a better effect.