Author(s)/Editor(s): Alan P Jeary | Size: 7,2 MB | Format:PDF | Quality:Unspecified | Publisher: University College London | Year: 1981 | pages: 208
A study of the measurement, prediction and characterisation of
the dynamic behaviour of tall buildings is presented. Initially
a review of the history of tall buildings and the study of their
dynamic behaviour is presented. The characterisation of tall
buildings by conventional means and by the use of spectral
functions is considered.
The results of tests on twelve tall buildings and one quarter-scale
model are presented. The response of twelve of these structures
to wind excitation has been monitored, and, for the purpose of
calibration, all but one of the buildings has been excited
artificially by the use of eccentric mass vibrators. The handling
of deterministic and random data is considered and some new
techniques for their reduction are presented.
The introduction of a new vibrator system has allowed the study of
the dynamic characteristics of tall buildings with a greater
precision than has previously been possible. The new precision
has suggested reasons for the confusion which previously existed
in the assessment of dynamic characteristics of tall buildings,
and a new rationale for the prediction of natural frequencies and
damping ratios is presented.
Finally, currently popular methods for the prediction of the
response of tall buildings to wind excitation are considered and
comparisons have suggested several areas where research is
urgently needed.
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Abstract: The objective of this study is to assess the seismic behavior of reinforced concrete bridges with skew-angled seat-type abutments through a performance-based methodology. Special attention is given to the exploration of variations in the seismic behavior of such bridges with respect to the angle of skew. Post-earthquake reconnaissance studies have reported that larger values of skew angle adversely affect performance. The idiosyncratic, "multi-phasic," behavior of skew bridges--observed during initial simulations of the present study--led to the development of a novel assessment methodology. This methodology is applied to a comprehensive database of bridges, which comprise combinations of a variety of geometric properties including: (1) number of spans, (2) number of columns per bent, (3) column-bent height, (4) span arrangement, and (5) abutment skew angle. An extensive set of nonlinear response history analyses were conducted using distinct suites of ground motions representing records for rock and soil sites, and another set that contained pronounced velocity pulses. The findings indicate that demand parameters for skew-abutment bridges--e.g., deck rotation, abutment unseating, and column drift ratio--are generally higher than those for straight bridges. Through detailed investigations of the sensitivity of various response parameters to variations in bridge geometry and ground motion characteristics, we observed that bridges with larger abutment skew angles bear a higher probability of collapse due to excessive rotations. We also found that shear keys can play a major role in abating deck rotations and thus the probability of collapse. It was further observed that the resultant peak ground velocity (PGVres) is the most efficient ground motion intensity measure (IM) for assessing skewed bridges' seismic response.
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Seismic earth pressures on retaining structures in cohesionless soils
Author(s): Mikola, Roozbeh Geraili; Sitar, Nicholas
Published By:University of California
Published Year:2013
Size: 4,2 MB
Quality:Unspecified
Abstract: Observations of the performance of basement walls and retaining structures in recent
earthquakes show that failures of basement or deep excavation walls in earthquakes are rare even
if the structures were not designed for the actual intensity of the earthquake loading. Failures of
retaining structures are most commonly confined to waterfront structures retaining saturated
backfill with liquefaction being the critical factor in the failures. Failures of other types of
retaining structures are relatively rare and usually involve a more complex set of conditions, such
as sloping ground either above or below the retaining structure, or both. While some failures
have been observed, there is no evidence of a systemic problem with traditional static retaining
wall design even under quite severe loading conditions. No significant damage or failures of
retaining structures occurred in the recent earthquakes such as Wenchuan earthquake in China
(2008) and, or the large subduction zone earthquakes in Chile (2010) and Japan (2011).
Therefore, this experimental and analytical study was undertaken to develop a better
understanding of the distribution and magnitude of seismic earth pressures on cantilever
retaining structures.
The experimental component of the study consists of two sets of dynamic centrifuge
model experiments. In the first experiment two model structures representing basement type
setting were used, while in the second test a U-shaped channel with cantilever sides and a simple
cantilever wall were studied. All of these structures were chosen to be representative of typical
designs. Dry medium-dense sand with relative density on the order of from 75% to 80% was
used as backfill. Results obtained from the centrifuge experiments were subsequently used to
develop and calibrate a two-dimensional, nonlinear, finite difference model built on the FLAC
platform.
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Seismic earth pressures on retaining structures with cohesive backfills
Author(s): Candia Agusti, Gabriel; Sitar, Nicholas
Published By:The Earthquake Engineering Online Archive
Published Year:2013
Size: 8 MB
Quality:Unspecified
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Abstract: Report presents the results of centrifuge model experiments and numerical analyses of seismic response of retaining structures with cohesive backfill. The experimental results show that the static and seismic earth pressures increase linearly with depth and that the resultant acts at 0.35H-0.4H, as opposed to 0.5-0.6H assumed in current engineering practice. Overall, the results also show that typical retaining walls designed with a static factor of safety of 1.5 have enough strength capacity to resist ground accelerations up to 0.4g.
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UCB/GT-2013-02, University of California, Berkeley, Geotechnical Engineering
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Author(s)/Editor(s): I. Elishakoff, J. Arbocz, C.D. Babcock and A. Libai (Eds.) | Size: 16 MB | Format:PDF | Quality:Unspecified | Publisher: Academic Press, Elsevier | Year: 1988 | pages: 458 | ISBN: 9780444704740
This collection of papers, written by friends and colleagues of Josef Singer, presents a comprehensive and timely review of the theoretical mechanics of thin shell-structures. Topics of great current interest such as the buckling of composite plates and shells, the plastic buckling of thin-walled structures and the optimum design of buckling sensitive curved composite panels are examined by experts, using a great diversity of approaches, whereby theoretical predictions are compared with experimental results whenever possible. Other topics reviewed include the buckling and post-buckling behaviour of imperfect shells under different external static or dynamic loads and a variety of boundary conditions. Papers dealing with the vibration and the dynamic response of thin elastic bodies are also presented. A strong emphasis is made on the practical applications aspect in the theories presented. Thus engineers, research workers and students who are involved with the design and analysis of shell structures made of different materials, and subjected to various static and dynamic loads will find this volume an invaluable source of reference.
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Author(s)/Editor(s): George Z. Voyiadjis and Dimitrios Karamanlidis (Eds.) | Size: 9 MB | Format:PDF | Quality:Unspecified | Publisher: Academic Press, Elsevier | Year: 1990 | pages: 313 | ISBN: 9780444883667
Plates and shells play an important role in structural, mechanical, aerospace and manufacturing applications. The theory of plates and shells have advanced in the past two decades to handle more complicated problems that were previously beyond reach. In this book, the most recent advances in this area of research are documented. These include topics such as thick plate and shell analyses, finite rotations of shell structures, anisotropic thick plates, dynamic analysis, and laminated composite panels. The book is divided into two parts. In Part I, emphasis is placed on the theoretical aspects of the analysis of plates and shells, while Part II deals with modern applications. Numerous eminent researchers in the various areas of plate and shell analyses have contributed to this work which pays special attention to aspects of research such as theory, dynamic analysis, and composite plates and shells.
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Modelling and simulation aspects of performace-based wind engineering of tall buildings
Author(s)/Editor(s): GORDON HENRY CLANNACHAN | Size: 6,5 MB | Format:PDF | Quality:Unspecified | Publisher: University of Strathclyde, Glasgow | Year: 2012 | pages: 266
The study is concerned with developing an adequate Performance-Based Wind Engineering (PBWE) framework for tall building design. The focus is to introduce advanced modelling and simulation techniques to improve key analysis stages, namely by using Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM). The clearly defined five stage PBWE framework is realised and implemented using both existing and newly developed simulation components. The performance of the developed process is explored by comparative PBWE analyses to assess the wind-induced behaviour of two tall building designs with distinctly different cross sections; a regular rectangular cross section and an irregular „L‟-shaped cross section.
The performance of CFD was primarily dependent on the turbulence model. On the basis of an extensive validation study, the Reynolds-Averaged Navier-Stokes (RANS) model was able to adequately compute the mean pressure coefficients acting on the benchmark CAARC tall building. However, its inability to sustain the atmospheric turbulence resulted in a significant under-estimation of the top floor accelerations. Hence, it was concluded that the RANS model is not suitable for competent PBWE studies. The results showed that the Large Eddy Simulation (LES) model offered the closest alternative to wind tunnel testing. However, full LES was too computationally expensive to be used for the PBWE framework, and hence a hybrid RANS-LES simulation strategy was formulated as a compromise. This was considered to offer an appropriate representation of the wind-induced pressure field without prohibitive complexities emanating from a full LES model.
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This thesis is submitted in fulfilment of the requirements for
the degree of Doctor of Philosophy in the Department of Civil
Engineering, University of Strathclyde, Glasgow
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Navisworks® project review software products enable architecture, engineering, and construction professionals to holistically review integrated models and data with stakeholders to gain better control over project outcomes.
Used primarily in construction industries to complement 3D design packages (such as Autodesk Revit, AutoCAD, and MicroStation) Navisworks allows users to open and combine 3D models, navigate around them in real-time and review the model using a set of tools including comments, redlining, viewpoint, and measurements. A selection of plug-ins enhances the package adding interference detection, 4D time simulation, photorealistic rendering and PDF-like publishing.
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· explores a wide range of topics dealing with optimization in solid (structural) and fluid mechanics (including CFD)
· covers multidisciplinary optimization when one discipline deals with structures or fluids
· examines closely related fields that are relevant to structural or fluid optimization
· is the official journal of the International Society of Structural and Multidisciplinary Optimization (ISSMO)
The journal’s scope ranges from mathematical foundations of the field to algorithm and software development, and from benchmark examples to case studies of practical applications in structural, aero-space, mechanical, civil, chemical, naval and bio-engineering.
Fields such as computer-aided design and manufacturing, reliability analysis, artificial intelligence, system identification and modeling, inverse processes, computer simulation, bio-mechanics, bio-medical applications, nano-technology, MEMS, optics, chemical processes, computational biology, meta-modeling, DOE and active control of structures are covered when the topic is closely related to the optimization of structures or fluids.
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I now uploaded for 1989-1991 year
Be patient for rest year publication
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Numerical simulation of the wind flow around a tall building and its dynamic response to wind excitation
Author(s)/Editor(s): Julia Revuz | Size: 23/33 MB | Format:PDF | Quality:Unspecified | Publisher: Department of Civil Engineering, Faculty of Engineering, University of Nottingham | Year: 2011 | pages: 275
Wind action is particularly important for tall buildings, both in providing a significant
contribution to the dynamic overall loading on the structure and by affecting its
serviceability. Whereas low and medium-rise buildings are fairly rigid, tall structures
are characterized by a greater flexibility and a lower natural frequency, which is more
likely to be in the frequency range of wind gusts. In addition, wake effects, such as vortex
shedding, can become a significant problem for flexible structures when the vortex
shedding frequency is close to the natural frequency of the building.
The aim of the present thesis is to assess the validity of commercial CFD codes for
modelling the wind flow around a high-rise building, including the consideration of the
coupled dynamic response of the building to turbulent wind loading. Three intermediate
objectives are set.
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Thesis submitted to the University of Nottingham
for the degree of Doctor of Philosophy
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