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اطلاعات کتابشناختی
عنوان اصلی: كنترل ارتعاشات برج ميلاد تحت اثر بار باد با استفاده از ميراگر جرمي تنظيم ‌شده و ارائه يك نوع ميراگر جرمي نيمه ‌فعال نوين با سختي متغير
پدیدآورندگان : گروه مهندسي عمران-دانشكده فني (پديدآور)
نوع : متن
جنس : پايان نامه
صاحب محتوا :

کتابخانه دیجیتالی دانشگاه تهران

وضعیت نشر :
مشخصات فیزیکی : جلد1 - ص 173
خلاصه : A procedure for direct selection of weighting matrices in LQR control design for single-degree-of-freedom (SDOF) systems is presented. The effectiveness of the proposed method is demonstrated through an example. In continuation, the effects of actuator saturation on the peak and root-mean-square (RMS) responses of the actively controlled SDOF system are investigated. For this purpose, a series of simulations are conducted for a SDOF system subject to representative earthquakes. The results show that it is not necessary to utilize an actuator whose capacity is large enough so that all required control forces obtained by the control algorithm can be realized and utilization of an actuator with a maximum capacity equal to some fraction of the maximum required control force considerably diminishes the structural responses which may be comparable to the case where all control forces are realized. With a height of 435 m, Milad Tower, situated in north-west of Tehran, Iran, would be the fourth highest telecommunication tower of the world. This tower has the largest head structure amongst its counterparts. In present study, it is demonstrate that the upper part of the tower may have excessive wind-induced acceleration related vibrations beyond human comfort limit during wind events. The effectiveness of tuned mass damper (TMD) on suppression of wind-induced motion of Milad Tower is examined through mathematical analyses. The tower is modeled as a vertical linear cantilever beam, with 57 degrees-of-freedom. The fluctuating wind speed is assumed to be a stochastic process which is identified by an appropriate power spectral density function. Random vibration analyses are carried out to determine response statistics. The possible application of tuned mass dampers (TMDs) in suppressing wind-induced motions of the tower is investigated and a TMD is designed to be installed at the sky dome. The results clearly show that the designed TMD has a considerable influence on suppression of structural response of the tower below human comfort limits. The author believes that Milad Tower can be considered as a benchmark control problem for TV and telecommunication towers by the structural control community. An innovative design for a semi-active variable stiffness (SAVS) device is presented. This beam-like device is capable of altering its stiffness in a smooth manner between minimum and maximum levels using the variations of moment of inertia of an area as it rotates about a normal axis passing through its centroid. Analytical expressions for the stiffness of the proposed device have been derived. As an application of SAVS device in engineering, a semi-active tuned vibration absorber (SATVA) is developed which is capable of real-time retuning and operates effectively in broad band frequency excitations. A SDOF system coupled with the SATVA is considered. It is assumed that the excitation force arises from a rotating unbalance whose frequency varies with a constant acceleration and then reaches a steady-state operating condition. The absorber stiffness is tuned to the forcing frequency in real time. The effectiveness of SATVA is evaluated by comparing systemapos;s responses with those of the system with passive vibration absorber. The results show the salient features of the proposed SATVA in transient response reduction over the traditional passive vibration absorber. The effectiveness of magnetorheological (MR) damper in semi-active vibration control of a SDOF system under seismic excitation is investigated. Numerical simulations have been carried out for uncontrolled and controlled structures in both active and semi-active cases. It is shown that the semi-active control method can mitigate the structural vibrations like a fully active control system.
یادداشت :
كتابنامه: به انگليسي
چكيده: به فارسي
چكيده: به انگليسي
عنوان به انگليسي:Wind -induced vibraion control of Milad Tower by tuned mass damper and proposing a novel semi-active variable stiffness tuned vibration absorber
رشته عمران سازه
دكتري تخصصي
شناسه : oai:ut.ac.ir:thesis/1-42667
تاریخ ایجاد رکورد : 1387/1/18
تاریخ تغییر رکورد : 1387/6/18
قیمت شيء دیجیتال : دارای قیمت

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