Suzana Moreira Avila

PARAMETRIC STUDY ON MULTIPLE TUNED MASS DAMPERS USING INTERCONNECTED MASSES

In this paper, the dynamic performance of a controlled high building is numerically investigated considering the effects of different numbers of mass dampers and their interconnection. The numerical analysis is conducted on a 20-story building considered as a shear frame and reduced to an SDOF system by means of the mode-superposition method. The system is subjected to harmonic load. Numerical searches are conducted based on the Min. Max. procedure in order to obtain efficient interconnected (I) multiple tuned mass dampers (MTMD). Comparisons are made among the uncontrolled system, the system controlled by non-interconnected (NI) MTMD, and the system controlled by (I) MTMD in frequency and time domain. Both (NI) and (I) MTMD reduce significantly frequency response peak amplitude. It is observed that the (I) MTMD produces great reductions on maximum displacement, rms displacement, steady-state peak response, and story displacements close to the reductions obtained by (NI) MTMD using review parameters. Mass maximum displacements analysis shows that the space required for (I) MTMD installation is smaller than (NI) MTMD.

Tuned Mass Damper Inverted Pendulum to Reduce Offshore Wind Turbine Vibrations

Wind energy is in a fast development worldwide and is currently receiving great investments mostly for being a clean energy source. Advances in this area are resulting in increasingly high and slender wind turbines, intensifying vibrations in structures caused by its own operation and, also, by wind force. Searching a better performance leads to offshore devices, i.e. wind turbines installed at the ocean next to coast. These structures take advantage of wind forces generated by more intense and consistent wind with less turbulence in these regions. One of the conceptions for this kind of wind turbine is the floating device. A solution to the problem of excessive vibration, which has been studied by several researchers in recent years, is structural control. One of the structural control devices, already extensively studied and implemented in practice, is the Tuned Mass Damper (TMD). An alternative geometry for TMD is the pendulum absorber. However, previous studies have shown that pendulum TMD installed on floating wind turbines requires an excessive length, therefore a different approach is required. In this work it is proposed an inverted pendulum TMD to improve control performance in an offshore wind turbine modeled as an inverted pendulum. This device may be considered as a linear oscillator only for small vibration amplitudes. Numerical simulations are performed to define TMD parameters that improve the control device performance. Good performance is achieved. However, passive devices only work properly for the design frequency range, and wind forces are random type of excitations. Better results would be achieved if a robust control is developed. This study will serve as a basis for the proposition of a semi-active device.

Optimal configurations of composite multiple mass dampers in tall buildings

The effectiveness of multiple tuned mass dampers (MTMD) for suppressing harmonically forced oscillations is studied in the paper. In particular the influence of possible connections between the masses of the damper on the main system performance is investigated using four different configurations of a double mass damper. For this, a minimax procedure, which considers all dampers parameters and variables, is used to optimize each configuration and compare their influence on the minimum value of the maximum magnification factor of the main system. A parametric study shows that small variations in the MTMD parameters and the way in which the masses are connected have a marked influence on the main system response. This sensitivity gives the designer more freedom in choosing the proper damper configuration in a practical situation.

Cracking Influence on Dynamic Parameters of Reinforced Concrete Floors

In view of the need to satisfactorily provide good performance of structures in their service situations, it is desired to understand the influence of some reinforced concrete particularities on the dynamic parameters of the structure. These particularities are fundamental in static analysis of pavements design. Starting from spans, geometry, and structural typologies common in real buildings, this paper studies the influence of cracking and non-constant reinforcements on the vibration frequency of concrete floors. It is shown that the reinforced concrete properties significantly impact the floor’s dynamic parameters; this impact is stronger when the floor is slender and deformable. Some of the common structural typologies, as the ribbed/waffle slabs, are even more susceptible to those influence. Knowing the main variables that may be responsible for excessive vibration phenomenon, it was possible to prevent issues during the design process.

CONTROL METHOD FOR ADJACENT BUILDINGS CONSIDERING SOIL-STRUCTURE INTERACTION

Abstract. In recent years a vibration control technique, called structural coupling, has been studied. This technique consists on linking two neighboring buildings, through a coupling device, with the purpose of reducing dynamic response. It is possible to control both structures response simultaneously, which is precisely the attractiveness of the technique. Several researchers explored the effectiveness of various seismic control devices, in connecting two adjacent buildings, considering they are supported on a fixed base. However, in general, all structures interacts with the surrounding soil, what substantially affects the dynamic response, it is called soil-structure interaction (SSI). Considering SSI on structural coupling is still incipient in literature. This work aims to evaluate SSI influence on the performance of this control technique, besides of presenting a simple analysis methodology to this type of problem. The results found show that SSI effects cannot be neglected on dynamic analysis of coupled structures. It was verified that changes on system natural frequencies due to SSI are important since, depending on earthquake frequency components, it modifies also the dynamic response of the system. All analysis were performed using MATLAB software.

Seismic Response Control of Adjacent Buildings Connected by Viscous and Hybrid Dampers

This paper discusses the seismic response control of a building by connecting it to another adjacent building. Coupled buildings have demonstrated to be an attractive method to mitigate excessive dynamic responses. This paper studies the behavior of two structures connected by passive dampers and also considering local feedback control systems installed in each structure, an hybrid strategy. These feedback control systems are designed and operated independently using active devices with limited actuation capacity like force actuators. The governing differential equations of motion of the coupled system are derived and solved for relative displacement. The advantages and disadvantages of each control strategy are examined in order to determine the more appropriate one. Based on the present research results, general conclusions and recommendations are given for further studies.

Estudo do comportamento dinâmico de uma passarela de pedestres da cidade de Brasília

O avanco das tecnologias construtivas e o uso de materiais de alta resistencia tem possibilitado o projeto de estruturas cada vez mais leves e flexiveis. Dessa forma, essas estruturas sao mais sensiveis a vibracoes em baixas frequencias. Essa tendencia tem se apresentado tambem nos projetos de passarelas de pedestres nos ultimos anos. Os carregamentos produzidos por movimentos humanos caracterizam-se por funcoes periodicas de baixas frequencias que podem provocar desconforto e ate problemas de seguranca, uma vez que essas baixas frequencias podem resultar proximas das frequencias naturais dessas estruturas. No presente trabalho estuda-se o comportamento dinâmico de uma passarela de pedestres localizada na cidade de Brasilia quando submetida as acoes humanas de caminhar e correr. Para isso, foi realizada uma avaliacao numerica de seu desempenho, utilizando os limites de servico referentes a vibracoes, aplicaveis a passarelas de pedestres, encontrados na literatura.