Reducción de vibraciones en un edificio mediante la utilización de amortiguadores magnetoreológicos

Uno de los dispositivos de control semi-activo más prometedor es el amortiguador magnetoreológico (MR), el cual se compone de un cilindro hidráulico, bobinas magnéticas y un fluido estimulable, denominado fluido magnetoreológico, cuya principal particularidad es su habilidad para variar, de manera reversible, de un estado liquido lineal viscoso de libre flujo para un estado semi-sólido en apenas milisegundos, cuando es expuesto a un campo magnético. Esta peculiaridad hace de los amortiguadores MR una herramienta ideal para el control de sistemas estructurales, pues con ellos es posible administrar fuerzas de amortiguamiento de forma simple, rápida y segura a un costo relativamente bajo. En el presente trabajo se analiza la respuesta estructural de un edificio tipo pórtico de dos pisos controlado por un par de amortiguadores MR administrados por un regulador lineal cuadrático (LQR) asociado a un algoritmo de selección de señal de comando desarrollado en el controlador clipped optimal. Los resultados obtenidos mostraron reducciones superiores al 49% y 76%, respectivamente, de picos de respuesta y de valores RMS de respuesta

Experimental study of the neighborhood effects on the mean wind loading over two equivalent high-rise buildings

This paper presents a series of results with respect to the mean values of shear, base moment and torsion acting in a building obtained through an experimental wind tunnel study using the standard building proposed by the Commonwealth Advisory Aeronautical Research Council (CAARC) as building reference. In the loading determination, the interference of a neighboring building with similar geometric characteristics to the CAARC was simulated, considering variations of positioning and spacing in relation to the reference building. It was concluded that the presence of the neighboring building increased the mean loads in the reference building for a significant number of directions considered. In the case of the considered deviations and the proposed provisions by this study, it was concluded that the vicinity factor that would contemplate the majority of the results obtained in the tests should increase the wind loads by at least 60% in relation to the values obtained for the building reference considered in isolation

Estudo experimental sobre a intensidade da interferência produzida, pela presença de edifícios vizinhos, na ação do vento em um edifício alto

Os esforços médios atuantes em uma edificação devidos à ação do vento, podem ser significativamente alterados quando se considera a presença de um ou mais edifícios vizinhos. Tais alterações podem ser consideradas através da utilização de coeficientes que levem em conta a distância que o edifício vizinho está da edificação em estudo. O presente trabalho foi desenvolvido no intuito de verificar os valores atualmente adotados pela norma brasileira que regula a ação do vento em edificações. Com a utilização de um túnel de vento, foram feitos vários ensaios em um edifício padronizado considerando a presença de outros edifícios com dimensões idênticas próximos a ele. Considerou-se o afastamento entre os edifícios, além da quantidade e da disposição das edificações vizinhas. Pôde-se concluir que, de maneira geral, a presença das edificações vizinhas produziu a majoração dos esforços. As interferências, em muitas situações, elevaram os esforços acima dos índices sugeridos pela atual norma brasileira de ação do vento.The average strain on a building due to the action of the wind, can be significantly altered when considering the presence of one or more neighboring buildings. Such changes can be considered through the use of coefficients that take into account the distance that the neighboring building is from the building being studied. The present work was developed in order to verify the values currently adopted by the Brazilian standard that regulates the wind action in buildings. With the use of a wind tunnel, several tests were carried out in a standardized building considering the presence of other buildings with similar dimensions close to it. The distances between the buildings, the quantity and the layout of the neighboring buildings were taken into consideration. It was possible to conclude that, in general, the presence of the neighboring buildings produced an increase on the strain. Interference, in many situations, increased strain above the rates suggested by the current Brazilian wind action standard

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Reducción de vibraciones en un edificio mediante la utilización de amortiguadores magnetoreológicos

One of the most promising device of semi-active control is the magnetorheological (MR) damper, which consists of a hydraulic cylinder, magnetic coils and a stimulate fluid called magnetorheological fluid, whose main feature is its ability to vary from a linear viscous liquid free-flowing state to a semi-solid state in just milliseconds when exposed to a magnetic field. This peculiarity makes the MR dampers an ideal tool for the control of structural systems, because with them it's possible manage damping forces in a simple, fast and secure way to a relatively low cost. This paper analyzes the structural response of a two-story building controlled by a pair of MR dampers operated by a linear quadratic regulator (LQR) associated with a algorithm developed to choose command signal of the clipped optimal controller. The results showed reductions higher than 49% and 76% of peak response and RMS values of response, respectivelyUno de los dispositivos de control semi-activo más prometedor es el amortiguador magnetoreológico (MR), el cual se compone de un cilindro hidráulico, bobinas magnéticas y un fluido estimulable, denominado fluido magnetoreológico, cuya principal particularidad es su habilidad para variar, de manera reversible, de un estado liquido lineal viscoso de libre flujo para un estado semi-sólido en apenas milisegundos, cuando es expuesto a un campo magnético. Esta peculiaridad hace de los amortiguadores MR una herramienta ideal para el control de sistemas estructurales, pues con ellos es posible administrar fuerzas de amortiguamiento de forma simple, rápida y segura a un costo relativamente bajo. En el presente trabajo se analiza la respuesta estructural de un edificio tipo pórtico de dos pisos controlado por un par de amortiguadores MR administrados por un regulador lineal cuadrático (LQR) asociado a un algoritmo de selección de señal de comando desarrollado en el controlador clipped optimal. Los resultados obtenidos mostraron reducciones superiores al 49% y 76%, respectivamente, de picos de respuesta y de valores RMS de respuest

Control de vibraciones en una viga gerber utilizando amortiguadores de masa sintonizados

Una de las estrategias mas comúnmente usadas en el control estructural es la instalación de amortiguadores de masa sintonizados (AMS). Los amortiguadores de masa sintonizados consisten básicamente de una masa, un resorte y un amortiguador, los cuales son fijados en la estructura, sintonizando la frecuencia del amortiguador a una frecuencia particular de la misma, con el objetivo de hacer que el amortiguador absorba parte de la energía, disminuyendo la respuesta de la estructura frente a una carga dinámica. En el presente trabajo se analiza numéricamente por medio del software ANSYS, el número y la posición más eficiente de AMS, cuyos parámetros son obtenidos mediante las expresiones de Den Hartog y de Jangid, para una viga Gerber metálica. Los resultados obtenidos muestran reducciones en la respuesta dinámica máxima de la viga, superiores al 80% en los casos en que la excitación de la estructura era armónica y superiores al 45% en los casos en que la carga aplicada era aleatoria de tipo ruido blanco

Structural control using magnetorheological dampers governed bypredictive and dynamic inverse models

The present paper implements a novelty semi-active structural control design on a two-story building, with the aim of reducing vibrations caused by transient type loads. The analyzed structure corresponds to an experimental prototype that was fully characterized and modeled according to the diaphragm hypothesis. The controller used was based on the action of a pair of real magnetorheological (MR) dampers whose operation is emulated by the phenomenological model. These mechanisms are governed by a numerical system that is based on non-linear autoregressive model with exogenous inputs (NARX)-type artificial neural networks, which have the ability to determine the necessary optimal control forces and the voltages required for the development of these forces through a prediction model and an inverse model, which are pioneers in this kind of systems. The results obtained show that the control design based on neural networks that was developed in the present study is a reliable and efficient, achieving reductions of up to 69% for the peak response value.En este artículo se implementa um novedoso proyecto de control estructural numérico en una edificación de dos pisos con el objetivo de reducir vibraciones debidas a cargas de tipo transiente. La estructura analizada corresponde a un prototipo experimental debidamente caracterizado y modelado de acuerdo con la hipótesis del diafragma. El controlador utilizado se basa en la acción de un par deamortiguadores magnetoreológicos (MR) reales cuyo funcionamiento es emulado a través del denominado modelo fenomenológico. Losdisipadores son gobernados por un sistema numérico basado en redes neuronales artificiales del tipo NARX con la capacidad de determinar fuerzas óptimas de control y voltajes a través de un modelo de predicción y un modelo inverso, los cuales son de uso inédito en este tipo de sistemas. Los resultados obtenidos muestran que el proyecto de control basado en redes neuronales desarrollado en este trabajo es un controlador confiable y eficiente, consiguiendo reducciones de hasta 69% en los valores pico de respuesta