PLASTIC buckling of plates and shells has been worked out by Bijlaard, Ilyushin, Stowell, Handelman and Prager, Gerard and others. Some investigators have assumed deformation type stress-strain laws while others have used incremental type (flow type) stress-strain laws. The present work is an extension of the work started by Gerard along the lines initiated by Stowell.
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Plastic buckling of cylindrical shells under biaxial loading
Author: J. J. Giezen, C. D. Babcock, J. Singer | Size: 758 KB | Format:PDF | Quality:Unspecified | Publisher: Springer | Year: 1991 | pages: 7
he predictions for plastic buckling of shells are significantly affected by the plasticity model employed, in particular in the case of nonproportional loading. A series of experiments on plastic buckling of cylindrical aluminum alloy shells under biaxial loading (external pressure and axial tension), with well-defined loading and boundary conditions, was therefore carried out to provide experimental data for evaluation of the suitability of different, plasticity models. In the experiments, initial imperfections and their growth under load were measured and special attention was paid to buckling detection and load path control. The Southwell plot was applied with success to smooth the results. The results show that axial tension decreases resistance to buckling under external pressure in the plastic region due to ‘softening’ of the material behavior. Comparison with numerical calculations usingJ 2 deformation and incremental theories indicate that both theories do not predict correctly plastic buckling under nonproportional loading.
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For elastic-plastic cylindrical shells with initial axisymmetric imperfections bifurcation into a non-axisymmetric shape is analysed. The shell material is represented by a phenomenological plasticity theory that accounts for the formation of a vertex on subsequent yield surfaces. The influence of various geometric and material parameters is investigated for a wide range of radius-to-thickness ratios. It is shown that for the thicker shells bifurcation generally occurs beyond the maximum axial compressive load. A few analyses for shells with additional non-axisymmetric imperfections show the unstable post-bifurcation behaviour and the sensitivity to imperfections of more general shapes.
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This paper focuses on the buckling of cylindrical shells with small thickness variations. Two important cases of thickness variation pattern are considered. Asymptotic formulas up to the second order of the thickness variation parameter ε are derived by the combination of the perturbation and weighted residual methods. The expressions obtained in this study reduce to Koiter's formulas, when only the first-order term of the thickness variation parameter is retained in the analysis. Results from the asymptotic formulas are compared with those obtained through the purely numerical techniques of the finite difference method and the shooting method.
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Article/eBook Full Name: Nonlinear Buckling Behaviour of Imperfect Cylindrical Shells under Global Bending in the Elastic-Plastic Range
Author(s): Lei Chen
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The most powerful aspects of myths are their ability to incite wonder and excitement. We're creating a myth that does these things while also challenging audiences to think.
The myth is that located in Rochester, NY, is the Escherian Stairwell, an architectural marvel that seems to violate the laws of physics and basic logic by looping back into itself. In order to lend credence to this myth, we're creating an episode for a family-friendly science show that demonstrates the staircase in action, various clips from a 1997 documentary with prominent thinkers grappling with the existence of this apparent contradiction and pontificating on its implications, and a whole slew of supplemental online materials for today's internet savvy audience to stumble across while trying to see if this thing is real (websites, scholarly articles, fan-pages, blogs, etc.). Help us build the myth!
Why create a myth?
Well, the short answer is that myths are awesome. Especially when done right. The slightly longer answer is that we are passionate about immersing audiences with a sense of wonder and surrounding them with a wealth of detail executed with such rigorous realism that they can choose to step into it, get lost in it, and believe in it. Films like Close Encounters and 2001 inspired us with awe, and even a hint of fear, when we first saw them. How do we capture that feeling again? The internet and the age of social media seem to be opening up doors to reinvent the medium and reignite those in-theater experiences that have gotten stale over the decades.
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REQUEST: Foundation Vibration Analysis Using Simple Physical Models
Author: John P. Wolf | Size: ?? MB | Format:PDF | Quality:Unspecified | Publisher: Prentice Hall | Year: May 21, 1994 | pages: 464 | ISBN: 0130107115, 9780130107114
This book provides simple physical models to represent the unbounded soil in time and frequency domain analysis. They do not supplant the more generally applicable rigorous methods, but rather supplement them. The physical models used consists of the following representations: cones based one-dimensional rod theory; lumped-parameter models with frequency-independent springs, dashpots, and masses; and prescribed wave patterns in the horizontal plane. The physical models thus offer a strength-of-materials approach to foundation dynamics.
From the Publisher
Offering a strength-of-materials approach to foundation dynamics, this volume shows how to use such simple physical models (cones, lumped-parameter models, and prescribed wave patterns in the horizontal plane) for analysis of foundation vibration problems that result from earthquakes, machine foundation, explosions, winds, and ocean waves on offshore platforms.
From the Back Cover
The rigorous methods used to model unbounded soil in large, complex projects are often not really appropriate for use in smaller, less critical projects. However, simple physical models are useful for the vast majority of foundation projects and they easily fit the budget and available time and require no sophisticated computer code. Offering a strength-of-materials approach to foundation dynamics, this volume shows how to use such simple physical models (cones, lumped-parameter models, and prescribed wave patterns in the horizontal plane) for analysis of foundation vibration problems that result from earthquakes, machine foundation, explosions, winds, and ocean waves on offshore platforms. Considers foundation on surface of homogeneous soil halfspace; foundation on surface of soil layer on rigid rock; embedded foundation and pile foundation; simple vertical dynamic-Green's function; seismic excitation; and dynamic soil-structure interaction. Features easy-to-use tables and detailed case studies. For geotechnical engineers, structural engineers, and engineering mechanics specialists.
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New closed-form formulae are presented for the torsional analysis of asymmetrical multi-storey buildings
braced by moment-resisting (and/or braced) frames, (coupled) shear walls and cores. The analysis is based
on an analogy between the bending and torsion of structural systems. A closed-form solution is presented
for the rotation of the building. The torsional behaviour is defi ned by three distinctive phenomena: warping
torsion, Saint-Venant torsion and the interaction between the two basic modes. Accordingly, the formula
for the maximum rotation of the building consists of three parts: the warping rotation is characterized by
the warping stiffness of the bracing system, St Venant rotation is associated with the St Venant stiffness
of the building and the third part is responsible for the interaction. It is demonstrated that the interaction
between the warping and St Venant modes is always benefi cial, as it reduces the rotation of the structure.
It is shown how the proposed formula for torsion can be used for the determination of the maximum defl ection
of multi-storey asymmetrical building structures. The results of a comprehensive accuracy analysis
demonstrate the validity of the method. A worked example is given to show the ease of use of the procedure.
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A large part of common reinforced concrete (RC) structures are designed as intermediate moment resisting
frames. However, current progressive collapse studies have not paid much attention to these frames. In this
study, based on the acceptance criteria of the UFC 4-023-03 document, the infl uence of some external and
corner column removal cases are evaluated by nonlinear procedures in all storeys of a regular structure.
Although this structure considers the acceptance criteria of nonlinear dynamic analyses, nonlinear static
analyses require additional reinforcement in beam supports in the top two storeys. Compared to dynamic
analyses, it is also concluded that static analyses are more conservative in the estimation of maximum
vertical displacement and shear force in beams.
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Exterior partially infi lled walls of RC condominium buildings are often monolithically cast with beams and/or columns in Taiwan. In practice, they are regarded as non-structural elements in usual structural design, and only their weight is conservatively considered. In this study, effects of three common types of exterior partially infi lled walls on the progressive collapse potential of an RC building are investigated.
Linear and nonlinear static analyses under different column-loss scenarios are carried out. Analysis results indicate that infl uence of the partially infi lled walls differs from each type. Changes in the demand-tocapacity ratios indicate that without considering the walls, the moment demand of beams may be overestimated.
However, their shear demand may be underestimated, especially with the panel-type walls. Meanwhile, they may increase the collapse resistance of the building frame under column loss but with decreased ductility capacity. From the structural aspect, with a constant opening rate of 60%, the wing-type wall is a better option than the parapet- and panel-type walls. The panel-type wall appears to be the worst choice since shear failure of their connected beam members may be induced.
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