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Dynamics of Coupled Large Amplitude Motions from Small Non-Rigid Molecules to Conjugated PolymersBhatta, Ram S. 06 December 2012 (has links)
No description available.
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Local Buckling of Doubly-Symmetric I-Sections Subjected to Warping Torsion : The limitations of the Reduced Cross-Section Method under unconventional loadingOri, Miklós January 2019 (has links)
In regular design practice, when it comes to conventional loading, such as uniaxial compression and bending, the local buckling of thin plates is taken care of through cross section classification. The effect of warping torsion, which also gives rise to normal stresses in the section, however, is typically not considered in the process. Present work aimed to uncover the influence of warping torsion on the phenomena of local plate buckling and to investigate the limitations of the effective width method when it was applied against its intended use. In the case of varying results, a simple correction to the calculation method was to be developed to improve accuracy. The examined I-sections were tested to failure and results were obtained with two different approaches: with finite element method and a Eurocode-based hand-calculation. The finite element models were refined to closely mimic physical experiments and their results were accepted as the true resistance of the sections, while the calculation method tried to capture the structural response in a practical, easily understandable way. The calculated results showed reasonably good accuracy with that of the finite element analysis. However, what really stood out was how similar the change in resistance was when the section parameters were manipulated. Through a properly chosen function, this allowed for the creation of an exponent that could modify the calculated results to achieve an even greater accuracy. The eccentricity of the applied load on the system was also manipulated to alter the proportion of normal stresses due to the two examined effects. It became clear that the stresses from warping in the applied calculation model were underestimated and the otherwise conservative method of effective width lost much of its safety margin when its application was extended to warping as well. Consequently, the consideration of stresses from warping in the regular design process and stability control of commonly used thin walled open sections seemed to be justified. The effective width method could not reliably cover the issue with retaining its original margin of safety.
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Seismic Performance of Symmetric Steel Moment Frames with Random Reactive Weight DistributionsWilliamson, Conner F.F. 01 December 2012 (has links) (PDF)
When a structure undergoes seismic excitation, the intensities and spatial distributions of the reactive weights on the structure may not be the same as those assumed in original design. Such a difference is inevitable due to many facts with the random nature (e.g., redistribution of live load), resulting in accidental eccentricity and consequently torsional response in the system. The added torsion can cause excessive deformation and premature failure of the lateral force resisting system and its detrimental effect is typically accounted for in most building design codes with an arbitrarily specified accidental eccentricity value. While it tends to amplify drift response of buildings under earthquake excitations, it is unclear whether the code specified accidental eccentricity is quantitatively adequate or not in seismic fragility assessment of steel moment frames (including low-rise, mid-rise and high-rise frames) with random reactive weight distributions. This thesis applies surveyed dead and live load intensities and distributions to three representative steel moment resisting frame structures that have been widely investigated in a series of projects under the collaboration of the Structural Engineers Association of California (SEAOC), the Applied Technology Council (ATC), and Consortium of Universities for Research in Earthquake Engineering (CUREE), known as SAC. Based on an extensive parametric study and incremental nonlinear dynamic analyses, it is found that variable load intensity and eccentricity had negligible impacts on the inter-story drifts of the low- and high-rise steel moment frames. However, they affect to a higher degree the performance of the mid-rise steel moment frames. Moreover, it is found that under the maximum considered earthquake (MCE) event, the actual drifts in steel moment frames with random reactive weight distributions can be conservatively captured through consideration of the code specified accidental eccentricities.
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Development of a Comprehensive Linear Response History Analysis Procedure for Seismic Load AnalysisTola, Adrian Patricio 11 March 2011 (has links)
This thesis reviews the parameters required to perform linear response history analysis according to Chapter 16 of the American Standard ASCE 7-10. A careful analysis is presented about the selection of ground motions using real records and using artificial records generated such that their response spectrum matches with a defined target spectrum; three different techniques are studied for the generation of these artificial records. Also, this document revises the scaling of ground motion techniques in the American Standard ASCE-7 as well as in other seismic codes. It presents a detailed analysis of the variables influencing the scaling of ground motions, and it suggests a new scaling technique for linear response history analysis. The assumptions made establishing the flexibility of the diaphragms are also analyzed as well as dynamic methods to include accidental torsion when doing a linear response history analysis. Other modeling issues such as the orientation of the ground motion axis, scaling of element forces and displacements, orthogonal loading, solution techniques, P-Delta effects, modeling of the basement, and calculation of drifts are also studied in the context of linear response history analysis. The thesis concludes with suggested code language for linear response history analysis intended to be considered in future editions of the American Standard ASCE 7. / Master of Science
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Three-dimensional non-linear finite element analysis of reinforced concrete beams in torsion. Reinforced concrete members under torsion and bending are analysed up to failure. A non-linear concrete model for general states of stress including compressive strength degradation due to cracking is described.Shaarbaf, Ihsan Ali Saib January 1990 (has links)
This thesis describes a non-linear finite element model suitable
for the analysis of reinforced concrete, or steel, structures under
general three-dimensional states of loading. The 20 noded
isoparametric brick element has been used to model the concrete and
reinforcing bars are idealised as axial members embedded within the
concrete elements. The compressive behaviour of concrete is
simulated by an elasto-plastic work hardening model followed by a
perfectly plastic plateau which is terminated at the onset the
. crushing. In tension, a smeared crack model with fixed orthogonal
cracks has been used with the inclusion of models for the retained
post-cracking stress and the reduced shear modulus.
The non-linear equations of equilibrium have been solved using an
incremental-iterative technique operating under load control. The
solution algorithms used are the standard and the modified
Newton-Raphson methods. Line searches have been implemented to
accelerate convergence. The numerical integration has been generally
carried out using 15 point Gaussian type rules. Results of a study
to investigate the performance of these rules show that the 15 point
rules are accurate and computationally efficient compared with the
27(3X3X3) point Gaussian rule.
The three- dimensional finite element model has been used to
investigate the problem of elasto-plastic torsion of homogeneous
members. The accuracy of the finite element solutions obtained for
beams of different cross-sections subjected to pure and warping
torsion have been assessed by comparing them with the available exact
or approximate analytical solutions.
Because the present work is devoted towards the analysis of
reinforced concrete members which fail in shear or torsional modes,
the computer program incorporates three models to account for the
degradation in the compressive strength of concrete due to presence
of tensile straining of transverse reinforcement. The numerical
solutions obtained for reinforced concrete panels under pure shear
and beams in torsion and combined torsion and bending reveal that the
inclusion of a model for reducing the compressive strength of cracked
concrete can significantly improve the correlation of the predicted
post-cracking stiffness and the computed ultimate loads with the
experimental results.
Parametric studies to investigate the effects of some important
material and solution parameters have been carried out. It is
concluded that in the presence of a compression strength reduction
model, the tension-stiffening parameters required for reinforced
concrete members under torsion should be similar to those used for
members in which bending dominates. / The scholarship of the Ministry of Higher Education of the Republic of Iraq.
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On large and small torsion pairsSentieri, Francesco 30 June 2022 (has links)
Torsion pairs were introduced by Dickson in 1966 as a generalization of the concept of torsion
abelian group to arbitrary abelian categories. Using torsion pairs, we can divide complex abelian
categories in smaller parts which are easier to understand.
In this thesis we discuss torsion pairs in the category of modules over a finite-dimensional algebra, in
particular we explore the relation between torsion pairs in the category of all modules and torsion
pairs in the category of finite-dimensional modules.
In the second chapter of the thesis, we present the analogue of a classical theorem of Auslander in the
context of τ-tilting theory: for a finite-dimensional algebra the number of torsion pairs in the
category of finite-dimensional modules is finite if and only if every brick over such algebra is finite-
dimensional.
In the third chapter, we revisit the Ingalls-Thomas correspondences between torsion pairs and wide
subcategories in the context of large torsion pairs. We provide a nice description of the resulting
wide subcategories and show that all such subcategories are coreflective.
In the final chapter, we describe mutation of cosilting modules in terms of an operation on the Ziegler
spectrum of the algebra.
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The effects of ultrasonic vibration, tension and torsion on the charge acceptance of the alkaline silver electrode ; II. Potentiostatic studies of the oxide growth rate law for the alkaline silver electrode ; III. The determination of ionic transport in silver oxide using radiotracer techniques with Ag[superscript 110m]Chase, Reed Harold 01 December 1976 (has links)
The effect of ultrasonic vibration on the anodic oxidation of silver foil in KOH was studied. An increase in charging capacity of approximately 20% was found to be the result of cavitation erosion. Silver wire was exposed to tension and torsion during oxidation but no change in charge acceptance was caused by these stresses. The oxide growth rate on silver foil electrodes was compared to rate equations that have been proposed for other metals. Uhlig's equations for the growth of semiconductor oxides was found to describe most of the data. The data did not fit other rate equations. Determination of the location of radioactive Ag110 in the oxide layer indicated that silver oxide grows by direct transport of the silver ion through the oxide, if a uniform oxide thickness is assumed. However, the dissolution-precipitation-model of oxide growth describes the data better and allows for the non-uniform oxide thickness which is characteristic of silver.
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Torsion in Homology of Random Simplicial ComplexesNewman, J. Andrew 11 October 2018 (has links)
No description available.
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On the computer aided design of a shaft subjected to reversed bending and steady torsionCurcio, Peter L. January 1987 (has links)
No description available.
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The Microstructural Evolution and Constitutive Analysis For A Phisical Simulation of Friction Stir Processing of Ti-6Al-4VLivingston, Jason James 22 July 2011 (has links)
No description available.
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