DYNAMIC RESPONSE OF BEAMS WITH PASSIVE TUNED MASS DAMPERS
Author: Mustafa Kemal Ozkan | Size: 2.5 MB | Format:PDF | Quality:Unspecified | Publisher: Purdue University West Lafayette, Indiana | Year: 2010 | pages: 275
Passive tuned mass damper (TMD) is a stand-alone vibrating system attached to a primary structure and designed to reduce vibration of the structure at selected frequency. This study focuses on the application of single or multipleTMDs on Euler-Bernoulli beams and examines their effectiveness based on free
and forced vibration characteristics of the beams, i.e., the primary structures. There is a gap in the existing literature in terms of free and forced vibration analysis of beams carrying any number of concentrated elements. There are methods developed for the free vibration analysis but they are not practical due to the complex mathematical expressions. Numerical assembly method (Wu and Chou, 1999) is used to determine free vibration characteristics of beams in order to get over the drawbacks of other approaches in the literature and forced vibration response is obtained based on modal analysis approach and orthogonality condition.
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PREDICTION OF FLOOR VIBRATION RESPONSE USING THE FINITE ELEMENT METHOD
Author: Michael J. Sladki | Size: 737 KB | Format:PDF | Quality:Unspecified | Publisher: December 1999 Blacksburg, Virginia 24061 | Year: 1999 | pages: 162
Several different aspects of floor vibrations were studied during this research. The focus of the research was on developing a computer modeling technique that will predict the fundamental frequency of vibration and the peak acceleration due to walking excitation as given in AISC Design Guide 11, Floor Vibrations Due to Human Activity (Murray, et al., 1997). For this research several test floors were constructed and tested, and this data was supplemented with test data from actual floors. A verification of the modeling techniques is presented first. Using classical results, an example from the Design Guide and the results of some previous research, the modeling techniques are shown to accurately predict the necessary results. Next the techniques were used on a series of floors and the results were compared to measured data and the predictions of the current design standard. Finally, conclusions are drawn concerning the success of the finite element modeling techniques, and recommendations for future research are discussed. In general, the finite element modeling techniques can reliably predict the fundamental frequency of a floor, but are unable to accurately predict the acceleration response of the floor to a given dynamic load.
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Energy Harvesting from Random Vibraitions of Piezoelectric Cantilevers and Stacks
Author: In Partial Fulfillment of the Requirements for the Degree Master of Science in Mechanical Engineering Georgia Institute of Technology August, 2013 | Size: 3.9 MB | Format:PDF | Quality:Unspecified | Year: 2013 | pages: 100
Electromechanical modeling efforts in the research field of vibration-based energy harvesting have been mostly focused on deterministic forms of vibrational input as in the typical
case of harmonic excitation at resonance. However, ambient vibrational energy often has broader frequency content than a single harmonic, and in many cases it is entirely stochastic. As
compared to the literature of harvesting deterministic forms of vibrational energy, few authors presented modeling approaches for energy harvesting from broadband random vibrations. These
efforts have combined the input statistical information with the single-degree-of-freedom (SDOF) dynamics of the energy harvester to express the electromechanical response
characteristics. In most cases, the vibrational input is assumed to have broadband frequency content, such as white noise. White noise has a flat power spectral density (PSD) that might in fact excite higher vibration modes of an electroelastic energy harvester. In particular, cantilevered piezoelectric energy harvesters constitute such continuous electroelastic systems
with more than one vibration mode.
The main component of this thesis presents analytical and numerical electroelastic modeling, simulations, and experimental validations of piezoelectric energy harvesting from
broadband random excitation. The modeling approach employed herein is based on distributed-
parameter electroelastic formulation to ensure that the effects of higher vibration modes are
included. The goal is to predict the expected value of the power output and the mean-square
shunted vibration response in terms of the given PSD or time history of the random vibrational
input. The analytical method is based on the PSD of random base excitation and distributed-
parameter frequency response functions of the coupled voltage output and shunted vibration
response. The first one of the two numerical solution methods employs the Fourier series representation of the base acceleration history in a Runge-Kutta-based ordinary differential
equation solver while the second method uses an Euler-Maruyama scheme to directly solve the
resulting electroelastic stochastic differential equations. The analytical and numerical simulations
are compared with several experiments for a brass-reinforced PZT-5H cantilever bimorph under
different random excitation levels. In addition to base-excited cantilevered configurations,
energy harvesting using prismatic piezoelectric stack configurations is investigated.
Electromechanical modeling and numerical simulations are given and validated through experiments for a multi-layer PZT-5H stack. After validating the electromechanical models for specific experimentally configurations and samples, various piezoelectric materials are compared theoretically for energy harvesting from random vibrations. Finally, energy harvesting from
narrowband random vibrations using both configurations are investigated theoretically and experimentally.
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Recent advances in structural technology require greater accuracy, efficiency, and speed in design of structural systems. It is therefore not surprising that new methods have been developed for optimal design of real-life structures and models with complex configurations and a large number of elements.
This book can be considered as an application of metaheuristic algorithms to optimal design of skeletal structures. The present book is addressed to those scientists and engineers, and their students, who wish to explore the potential of newly developed metaheuristics. The concepts presented in this book are not only applicable to skeletal structures and finite element models but can equally be used for design of other systems such as hydraulic and electrical networks.
This book is likely to be of interest to civil, mechanical, and electrical engineers who use optimization methods for design, as well as to those students and researchers in structural optimization who will find it to be necessary professional reading.
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Using Non-Linear Vibration Techniques to Detect Damage in Concrete Bridges
Author: S.A. Neild Department of Engineering Science, University of Oxford. | Size: 5.1 MB | Format:PDF | Quality:Unspecified | Year: 2001 | pages: 294
There has been much work published in recent years on the use of vibration char-
acteristics to detect damage in bridges. Almost all of this work has been based on the
assumption that the vibration is linear, i.e. the natural frequencies are not dependent on
the amplitude of oscillation. The aim of the work presented here was to investigate the
possibility of using changes in the non-linear vibration characteristics to detect damage
in reinforced concrete bridges.
These changes in the non-linear vibration characteristics were studied by conducting
impact excitation vibration tests on reinforced concrete beams. The non-linearities
were detected by examining the changes in fundamental frequency over time (and hence
over amplitude of vibration). Several time-frequency distribution estimation tools are
discussed including the discrete Fourier transform moving window, the auto-regressive
model moving window, harmonic wavelets and examples of the Cohen class of bilinear
time-frequency distributions. A detailed investigation into these various distribution
predictors was conducted to assess which is most suitable for analysing the vibration
signals to detect changes in frequency with time.
To understand the non-linearities in the vibration characteristics, a time-stepping
model was described. The model is capable of including damage in the form of a moment-
rotation relationship over the cracked region. It was validated for linear vibrations
against theoretical values and the representation of a non-linear mechanism using the
model was compared with experimental data.
Static load tests were also conducted on the beams at various damage levels. They
involved the use of vibrating wire strain gauges to investigate the moment-rotation be-
haviour over the cracked region. Several possible non-linear crack mechanisms are dis-
cussed and two of them are assessed using the vibration and the static load tests. Future
experimental work is proposed to study the possible non-linear mechanisms further.
The beam tests demonstrated that there is a change in non-linear vibration behaviour
with damage. The change is greatest at low levels of damage and after the beam has
been loaded to 30% of the failure load in three-point loading there is a reversal in the
trend and a slight reduction in non-linearity with further damage.
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Genetic Programming: On the Programming of Computers by Means of Natural Selection (Complex Adaptive Systems)
Author: John R Koza | Size: 5 MB | Format:PDF | Quality:Unspecified | Publisher: MIT Press | Year: 1992 | pages: 609 | ISBN: 0262111705/9780262111706
Genetic programming may be more powerful than neural networks and other machine learning techniques, able to solve problems in a wider range of disciplines. In this ground-breaking book, John Koza shows how this remarkable paradigm works and provides substantial empirical evidence that solutions to a great variety of problems from many different fields can be found by genetically breeding populations of computer programs. Genetic Programming contains a great many worked examples and includes a sample computer code that will allow readers to run their own programs.In getting computers to solve problems without being explicitly programmed, Koza stresses two points: that seemingly different problems from a variety of fields can be reformulated as problems of program induction, and that the recently developed genetic programming paradigm provides a way to search the space of possible computer programs for a highly fit individual computer program to solve the problems of program induction. Good programs are found by evolving them in a computer against a fitness measure instead of by sitting down and writing them.John R. Koza is Consulting Associate Professor in the Computer Science Department at Stanford University.
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This code provides minimum requirements for design and construction of reinforced concrete and prestressed concrete structures for the storage and containment of refrigerated liquefied gases (RLG) with service temperatures between +40 and –325°F. The principles listed herein are applicable to concrete foundations of double-steel tanks subject to the approval of the owner.
Container design shall include the design of the container wall, its foundation (footing and floor slab), the concrete portions of its roof, and the bund wall, whenever applicable. Available in hard copy or electronic format.
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ENA Doc 018-2008 ENA Interim Guideline for the Fire Protection of Electricity Substations. The overall scope of the Guideline is to be outlined including relevance to new and existing substations. Some of the objectives are; - compliance with all relevant legislation - meeting functional
Mark magazine is a platform for the practice and perception of architecture at the dawn of the third millennium. Since its launch in 2005, the magazine has proven to be a timely, visual, non-academic publication full of first-hand information from creative people. Mark has a radically international perspective, shining its spotlight on starchitects and new talent alike. The magazine explores the boundaries of architecture and anticipates the industry’s future.
Mark #51 Aug/Sep 2014
Articles on China’s building boom often highlight the property bubble, megalomaniac planners, governmental corruption and private graft, substandard building practices and the destruction of the nation’s cultural heritage.
In Mark #51, we interviewed four Chinese architects on four aspects of China’s building practices to reveal the mechanisms at the foundation of this unedifying image. Li Hu offers his thoughts on architecture, Liu Yuyang on urban planning, Li Xiaodong on aesthetics and Liu Jiakun on construction processes. What can we learn from their experience?
Then we make a short stop in the Netherlands and visit the renovated love-it-or-hate-it TivoliVredenburg in Utrecht, orchestrated by Herman Hertzberger and take a guided tour of Neuteling Riedijk’s Eemhuis cultural centre in Amersfoort. Our reporters shed a spotlight on social notworking at Rem Koolhaas’ Venice Biennale before marvelling at the glacial forms of Zaha Hadid’s Innovation Tower in Hong Kong. Moving on to Argentina, we look at the latest creations from the up-and-coming duo Adamo-Faiden Architects before reviewing an immaculately crisp retirement complex for Portugese bankers by Guedes Cruz Architects.
Photographer and writer Sergio Pirrone invites us to contemplate the loss of structural derring-do in contemporary Japanese architecture. Perhaps technical innovation simply moved continents, for Odile Decq serves up an audacious exercise in steel trusses and cantilevers in a Lyon office building in France whilst MBA/S completes a crystalline Stuttgart residence out of insulating concrete, a first in Germany. After this whirlwind world-tour we wind down with Aaron Betsky who explains the evocative power of books and films.
Cross Section:
Palatium Stúdió, Woods Bagot, Ken Wong, Marc Mimram, Warren Techentin, Makiko Tsukada, Peter Wenham, Coop Himmelb(l)au, Theo Deutinger, Yuusuke Karasawa, MJosé van Hee, A69, Search
Perspective: ‘We build too much too fast.’
Open Architecture in Beijing: Li Hu would like architects to reconsider the concepts their cities are built on.
Atelier Liu Yuyang Architects in Shanghai: Liu Yuyang talks about the urban development of Shanghai and the principle of China’s urbanization.
Li Xiaodong Atelier, Beijing: Li Xiaodong doesn’t think that high-rises and organically shaped museums is the way for Chinese architecture to move ahead.
Jiakun Architects in Chengdu: Liu Jiakun has found a way to deal with the lack of craftsmanship in the construction industry.
Long Section:
Architectuurstudio HH in Utrecht, The Netherlands: Those who are not put off by the outer appearance of the new music palace will find a temptation-filled temple inside.
Neutelings Riedijk Architects in Amersfoort, The Netherlands: The architects wrapped a cultural centre in an undisguised reference to George, the city’s patron saint.
Groupies in Venice, Italy: Our reporters explore group dynamic, team spirit, social interaction and politics at the Architecture Biennale.
Zaha Hadid Architects in Honk Kong, China: The starchitect’s Innovation Tower provides its students something of the subtlety and complexity of a natural landscape.
Adamo-Faiden Architects in Buenos Aires, Argentina: Sebastián Adamo and Marcelo Faiden aim for an architecture that is rooted in society while also producing friction.
Guedes Cruz Architects in Alcadideche, Portugal: A retirement home for former bank employees that might resemble a series of mausoleums.
Searching for Masahiro Ikeda in Japan: Sergio Pirrone looks for the genius structural engineer behind Japan’s experimental architecture of the previous decade.
Studio Odile Decq in Lyon, France: The architect’s latest office building takes its cues from steel-truss bridges and cranes.
MBA/S in Stuttgart, Germany: The first house in the country to be built out of thermally insulating concrete.
Aaron Betsky in Cincinatti, USA: The way we live in books can be as vivid as the way we live in physical structures.
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