ABSTRACT
In order to determine the effectiveness of adding viscoelastic dampers to structures on the reduction of their seismic response, a comprehensive analytical and experimental program
was carried out. The experimental program was first conducted on a 2/5-scale five-story steel frame under precisely controlled ambient temperatures and subject to simulated ground motions with peak accelerations ranging from 0.12g to 0.60g. Results show that viscoelastic dampers are very effective in attenuating seismic structural response at all levels of earthquake ground motions, and that their energy dissipation capacity decreases as ambient temperature increases. However, they are effective at all temperatures tested in the research program. A rational seismic design procedure for viscoelastically damped structure is developed based on these results.
Further tests using a full-scale prototype structure confirm that damping in the full-scale structure can be significantly increased by adding relatively small viscoelastic dampers. The damper design procedure developed based on the scaled model can also be applied to the full-scale structure. This full-scale analytical and experimental study provides an important base for applying the extensive data generated from the scaled model testing to the full-scale structures.
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The protective and intelligent systems program constitutes one of the important areas of research
in the Building Project. Current tasks include the following:
1. Evaluate the performance of full-scale active bracing and active mass dampers already in place in terms of performance, power requirements, maintenance, reliability and cost.
2. Compare passive and active control strategies in. terms of structural type, degree of effectiveness, cost and long-term reliability.
3. Perform fundamental studies of hybrid control.
4. Develop and test hybrid control systems.
NCEER's activities in viscoelastic dampers research for seismic applications began in 1987 with analytical and experimental work carried out at the State University of New York at Buffalo and at the University of California at Berkeley. The ultimate aim is to determine their effectiveness when incorporated into a structure under seismic loads, and to develop a rational design procedure for such structures. This report summarizes results of a comprehensive analytical and experimental program for steel frame structures. The experimental program was first conducted on a 215-scale steel frame in the laboratory, followed by verification tests conducted on a full-scale prototype structure. A rational seismic design procedure for viscoelastically damped steel frame structures is developed based on these results.
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Sorry, if this inquiry is too simplistic, but I have not been able to figure out how to view Posts for a particluar date.
For example, how do I search to view posts from November 01, 2011?
Thanks for your help.
Mobile equipment for continious handling of bulk materials -
Part 1:
Rules for the design of steel structures
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Hi
Please share this document; Introduction for ABAQUS-CFD
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This dissertation develops a new multi-criteria decision support framework for conducting multi-hazard design and retrofit of seismic- and wind-excited structures with passive energy dissipation PED) devices. In addition to designing in compliance with the relevant codes of practice, it is important to note that the performance of PED devices for reducing the structural responses depends on the type, size, and distribution of dampers. The proposed framework provides a genetic algorithm GA) based methodology to address these optimization issues of structural control systems within the context of nonlinear structures. Steel buckling restrained braces, viscous fluid dampers and solid viscoelastic dampers are all considered as possible design alternatives within this framework. In the proposed algorithm, passively damped structural designs evolve toward configurations that limit damage associated with inter-story drift and absolute peak floor acceleration, while considering essential conflicts in dynamic response demands of the structures under different hazard environments, involving earthquakes and strong windstorms. Optimal design of passively damped structures in such uncertain hazardous environments requires not only choosing the most cost-effective approach from a series of alternatives but also defining project-specific constraints and the risk associated with each decision alternative. Thus, unlike previous work in PED optimization, the proposed framework introduces a newly developed multi-objective genetic algorithm to accelerate the convergence to the robust design solutions and to maximize the overall benefit of the structural control system. Additionally, a probability-based optimization approach is introduced to allow decision makers to achieve a specific performance objective, such as identifying the retrofitting investments that will result in minimum life-cycle cost impact on a building. This new approach uses weighted life-cycle cost as an objective function to permit consideration of risk aversion by accounting for uncertainty related to earthquake frequency, structural vulnerability, cost of structural damage and retrofitting, and mitigation benefits. The proposed optimization framework is applied to several example buildings designed or retrofitted with passive control devices to demonstrate the effectiveness of the optimization approaches. From the illustrative examples, it is positively concluded that the modular framework can be successfully used as a practical decision-making tool for cost-effective optimal multiple hazard design of passively damped structures. Also, it is shown that the probability-based optimization approach results in design or retrofit alternatives that combine well with the performance-based design concept, with usage of more realistic design criteria, such as expected life-cycle cost of meeting prescribed performance level.
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Investigation of pushover analysis procedures for reliability-based and performance-based seismic design with applications to asymmetric building structures
In 1995, a framework for a reliability-based, performance-based seismic design procedure was proposed by Collins. The basic idea behind the procedure was to develop an equivalent single-degree-of-freedom (SDOF) model of the structure and then to use this model and uniform hazard spectra to predict maximum displacements and drifts in the multi-degree-of-freedom (MDOF) structure. Deterministic design-checking equations based on the equivalent SDOF system were developed,and design factors (analogous to load and resistance factors) were calibrated and used in design-checking equations to account for the uncertainty in the equivalent SDOF model, the seismic environment, and site soil conditions. The parameters of the SDOF model were obtained using information from two-dimensional static pushover analyses of the lateral force resisting systems of the structure.
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online spreadsheet for DESIGN OF ISOLATION SYSTEM FOR BRIDGES :
in metric and us units :
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Plate tectonic collision, climate oscillation, glacial fluctuation, severe wind and water erosion - all have wrought dramatic change on the landscape of the Western Himalaya, one of the most dynamic and spectacular landscapes on Earth. Study of the region - from the Western Himalaya foothills and lowlands to the Arabian Sea - is of particular value to geology and geomorphology because of the size and frequency of events. That much of South Asia is relatively inaccessible has enhanced the significance of research in Pakistan and adjacent areas. Himalaya to the Sea focuses on the general evolution of landforms in Pakistan but is also an essential guide for predictive, protective and remedial measures to mitigate the natural hazards which plague the region and constrain development. The authors describe regional erosion and sedimentation within the context of topographical evolution; more specifically, they deal with neotectonics, past and present glaciation, general mountain geomorphology and process mechanics, past and present fluvial processes and landforms, wind blown loess deposits, age dates, soils, marine terraces and archaeology. This is the first integrated assessment of the geomorphology and Quaternary evolution of this region, from highlands to ocean. Presenting new research, methodologies and theory, this highly illustrated book also provides the first comprehensive bibliography to this exciting region.
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Posted by: shadabg - 11-05-2012, 11:13 AM - Forum: Geology
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History of Geomorphology and Quaternary Geology - Special Publication no 301
Author: R. H. Grapes, D. R. Oldroyd, A. Grigelis | Size: 13.8 MB | Format:PDF | Quality:Original preprint | Publisher: Geological Society of London | Year: 2008 | pages: 344 | ISBN: 1862392552
This book deals with various interesting aspects of the histories of geomorphology and Quaternary geology in different parts of the world. The papers cover a range of topics: the origin of the term 'Quaternary', histories of ideas and debates relating to aspects of fluvial geomorphology (USA and Australia), glacial geomorphology and glaciation (Northern Europe, the Baltic countries, Russia, Iceland, and New Zealand), desert dunes and the geology of Australia, peneplains in China, a palaeo-Tokyo Bay in Japan, together with biographies of Charles Cotton (New Zealand), Valerija Cepulyte (Lithuania) and Ceslovas Pakuckas (Lithuania and Poland) that highlight their respective contributions to the disciplines of geomorphology and Quaternary geology. There is an autobiographical contribution from E. E. Milanovsky (Russia) on his work in Siberia, the Caucasus and Iceland, illustrated by his sketches made in the field.
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Dear Friends
I have been searching about the use of gunite, shotcrete or "sprayed concrete" in new Construction.
Especially their use in building walls, columns, beams for new construction
Gunite or Shotcrete has been in use for tunnel construction ( it is not my interest)
Any material, literature will be appreciated.
Thanks in advance
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