Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 61-68).

Στόχος της παρούσας εργασίας είναι η παραμετρική μελέτη μεταλλικών καμπτικών επίπεδων πλαισίων με υποστυλώματα διατομής τύπου τετραγωνικής κοιλοδοκού (Square Hollow Section, SHS) και δοκών διατομής τύπου διπλού ταυ (IPE). Ζητούμενο αποτελεί η ανάπτυξη εξισώσεων που συνδέουν χαρακτηριστικά της ανελαστικής απόκρισης των κατασκευών. Βασική επιδίωξη είναι η δυνατότητα πραγματοποίησης αντισεισμικού σχεδιασμού σύμφωνα με την μέθοδο των δυνάμεων έχοντας όμως σαν αρχικό στόχο ένα επιθυμητό επίπεδο επιτελεστικότητας σύμφωνα με τη μέθοδο σχεδιασμού που βασίζεται στις μετακινήσεις. Επίσης, αναπτύχθηκαν εξισώσεις που προβλέπουν την καθ’ ύψος κατανομή των ελαστικών και ανελαστικών μετακινήσεων της κατασκευής. Αναδεικνύεται η επιρροή του ελέγχου ευστάθειας στον σχεδιασμό μεταλλικών καμπτικών πλαισίων. Χρησιμοποιούνται διάφορες παράμετροι που εκτιμήθηκε πως επηρεάζουν την ελαστική και ανελαστική απόκριση των κατασκευών όπως το όριο διαρροής του χάλυβα fy των μελών, ο αριθμός των ορόφων ns, που επηρεάζει άμεσα την ιδιοπερίοδο του συστήματος, η μορφή της ελαστικής απόκρισης των κατασκευών, οι οποίες διακρίνονται σε καμπτικού και διατμητικού τύπου (shear type, flexural type) σύμφωνα με τον συντελεστή ρ όπως ορίζεται από τον Chopra (2007a), καθώς επίσης και την παράμετρο πλαστικών ροπών a που σχετίζεται με το είδος του αναπτυσσόμενου ανελαστικού μηχανισμού. Ο υστερητικός νόμος που χρησιμοποιήθηκε και περιγράφει την ανελαστική απόκριση των μελών υπό ανακυκλιζόμενη δράση, ταυτίζεται με τον διγραμμικό υστερητικό νόμο με κράτυνση 3% προσομοιώντοντας παράλληλα και την απομείωση της αντοχής των μελών που συνδέεται άμεσα με την τοπική πλαστιμότητα τους σε κάθε ανελαστικό κύκλο φόρτισης. Παραμετρικές αναλύσεις έγιναν επίσης με τη χρήση διγραμμικού νόμου υστέρησης με κράτυνση 3% χωρίς την απομείωσης της αντοχής των μελών κατά την ανελαστική τους απόκριση, με στόχο την διερεύνηση της επιρροής στην αντοχή των μελών κατά την ανελαστική τους απόκριση. Για την πραγματοποίηση της παρούσας μελέτης 57 καταγραφές παρελθοντικών σεισμών μακριά από το σεισμικό ρήγμα, αποτέλεσαν την διέγερση για την εκτέλεση των δυναμικών μη-γραμμικών αναλύσεων ώστε να ληφθεί υπόψη η επιρροή του συχνοτικού περιεχομένου των επιταχυνσιογραφημάτων στην απόκριση των συστημάτων. Τέλος, παραδείγματα που συγκρίνουν την μέθοδο που παρουσιάζεται με την μέθοδο των δυνάμεων αποδεικνύουν την αποτελεσματικότητα της μεθόδου. / An efficient procedure to estimate an orthological value of the strength reduction factor q of the European seismic code based on a target performance level is presented. Several parameters that affect the elastic and inelastic response of the planar steel moment resisting frames are taking into account. The simple bilinear hysteretic rule is been used to model the inelastic response of the members by including the degradation of their strength. The comparison of the inelastic response of the structures with and without degradation of strength is showed. Examples are evaluating the efficiency of the chosen strength reduction factor and they are demonstrating the dominant role of the second order effects that restrict the seismic design of steel moment resisting frames at high performance levels.

No description available.

[pt] A modelagem do acoplamento entre os fenômenos mecânicos e térmicos em sólidos inelásticos é considerada neste trabalho. O acoplamento termomecânico é importante em determinadas situações, como por exemplo, no estudo de problemas envolvendo deformações inelásticas cíclicas em estruturas metálicas. Um procedimento sistemático para obtenção de equações constitutivas termodinamicamente admissíveis é apresentado. Através deste procedimento, baseado na Termodinâmica dos Processos Irreversíveis, foi possível obter uma teoria constitutiva para modelar o comportamento anisotérmico de metais e ligas metálicas. Dois tipos de acoplamentos termomecânicos foram identificados: o acoplamento interno, associado à dissipação interna do processo mecânico, e o térmico, associado à dependência dos parâmetros das equações constitutivas com a temperatura. A teoria foi particularizada para materiais elasto-viscoplásticos. Simulações com barras foram realizadas para estudar fenômenos como o aquecimento de metais provocado por solicitações mecânicas complexas e o comportamento de metais submetidos a grandes gradientes de temperatura. Uma variável de dano foi incorporada ao modelo, permitindo estudar a influência do acoplamento termodinâmico em processos de degradação do material como fadiga de baixo ciclo. / [en] The present work is concerned with the modeling of the coupling between mechanical and termal phenomena. The thermomechanical coupling is important in some problems like those involving inelastic cyclic deformation in metallic structures. A systematic procedure to obtain thermodynamically admissible constitutive equations is presented. Such procedure has a strong thermodynamic basis and is used to obtain a constant theory to model the anisothermal behavior of metals and alloys. Two kinds of thermomechanical couplings can be identified: the internal coupling, related with the internal dissipation in the mechanical process and the thermal coupling, related with the dependence of the material parameters in the constitutive equations on temperature. The theory is particularized to elasto-viscoplastic materials. Uniaxial simulations were performed to study the heating of metals due to complex mechanical loadings and the behavior of metals subjected to high temperature gradients. A damage variable is introduced in the model to study the influence of the thermomechanical coupling in processes involving the degradation of the material like in low-cycle fatigue.

[pt] Neste trabalho, apresentam-se modelos mecânicos para previsão da integridade estrutural de tubulações anelásticas conduzindo líquidos, submetidas a transientes hidráulicos. A descrição do fenômeno de transiente hidráulico é feita com base em duas formulações unidimensionais: uma acoplada e outra desacoplada. A formulação acoplada considera a interação dinâmica fluido-estrutura entre os movimentos do fluido e do tubo, enquanto que a desacoplada refere-se ao modelo tradicional de golpe de ariete. A integridade da tubulação é modelada com base na Mecânica do Dano Continuo. O comportamento anelástico da parede do tubo assim como o dano induzido pela deformação anelástica são descritos por uma teoria constitutiva com variáveis internas e forte respaldo termodinâmico. A teoria engloba um grande número de equações constitutivas encontradas na literatura e permite descrever diferentes respostas mecânicas numa mesma estrutura matemática. As equações resultantes para ambos os modelos - acoplado e desacoplado - formam um sistema não linear de equações diferenciais parciais hiperbólicas. Apesar da forte não linearidade, mostra-se que métodos numéricos clássicos podem ser empregados para resolver as equações quando se utiliza uma técnica de decomposição do operador. No trabalho, emprega-se entre outros o método de Glimm. Exemplos numéricos que retratam a evolução do dano induzida por transientes de pressão em tubulações elasto-viscopláticas são apresentados e analisados. Comparações realizadas entre as previsões dos modelos e entre simulações com e sem dano permitem, na análise, caracterizar as influências do acoplamento fluido-estrutura e do dano. / [en] This work presents mechanical models for structural failure prediction of compliant inelastic pipings conveying liquids, submitted to hydraulic transients. Hydraulic transients are described based on two, a coupled and an uncoupled, onedimensional formulations. The coupled formulation takes into account the dynamical fluid-structure interaction between fluid flow and pipewall motions, whereas the uncoupled one refers to the well-known waterhammer model. Piping integrity is modelled on the basis of the Continuum bamage Mechanics. Both pipewall inelastic mechanical behavior and damage induced by inelastic deformations are described by an internal variable constitutive theory with strong thermodynamical support. It encompasses a great number of constitutive equations found in the literature and allows the treatment of several different mechanical responses within a same mathematical framework. The resulting equations of both coupled and uncoupled transient models forma non linear system of hyperbolic partial differential equations. In spite of its strong non linearity, it is shown that classical numerical methods can be used for solving the equations whether a operator splitting technique is employed. Among others, Glimm s scheme has been used in this work. Numerical examples concerning the damage evolution induced by pressure transients in elasto-viscoplastic pipings are presented and analysed. Comparisons between the predictions of the models and simulations with and without damage are presented, so that the fluid-structure coupling and the damage influences on the analysis are investigated.

This thesis presents a joint experimental and theoretical study of vector correlations in the electronically, vibrationally, and rotationally inelastic collisions of simple molecules with rare-gas atoms. In the first instance, empirical and calculated data are presented for rotationally inelastic scattering in the NO(X)+Ar and ND₃(X̃)+Ar systems at collision energies in the range 405-2210 cm^-1. These experiments - the first to be conducted on a newly commissioned crossed-molecular beam machine - measured the k-k' correlation, i.e. that between the vectors describing the relative velocities before and after collision, respectively. The empirical data were subjected to rigorous comparison with both quantum-mechanical and quasi-classical trajectory (QCT) calculations. For both the NO(X)+Ar and ND₃(X̃)+Ar systems, there is generally good agreement between experiment and theory at all four collision energies investigated. Two chapters of this thesis focus on the development of trajectory surface-hopping (TSH) QCT models of the OH(A, v = 0)+Kr and OH(A, v = 0)+Xe systems. Experimental data relating to scalar quantities (rotational energy transfer (RET) and electronic quenching) and to the j-j' correlation (which quantifies the depolarisation of the angular momentum of the OH(A) radical) are compared to variable-collision-energy TSH QCT calculations in which the length of the OH bond is fixed. The algorithms involve all three PESs of the OH(A/X)+Kr system, and the full range of electrostatic and roto-electronic mechanisms that couple them, for the first time. The most complete model succeeded in accounting for 93% of experimentally observed quenching. For the OH(A/X)+Xe system, coupling matrix elements were estimated from those of OH(A/X)+Kr, and the most complete model recovered 63% of experimentally observed quenching. This thesis also presents a novel theoretical study of rotationally inelastic dynamics in the OH(A, v = 1)+Kr system. Provisional results from adiabatic calculations in which the OH bond length is allowed to vary over the course of a trajectory are presented alongside experimental data that were reported previously. To date, these calculations continue to underestimate the extent of empirical RET data. Reasons for the observed discrepancy, and suggestions to resolve it, are outlined in detail.

Non-Newtonian fluids are of great scientific interest due to their range of physical properties, which arise from the characteristic shear stress-shear rate relation for each fluid. The applications of non-Newtonian fluids are widespread and occur in many industrial (e.g. lubricants, suspensions, paints, etc.) and environmental (e.g. mud, ice, blood, etc.) problems, often involving multiple fluids. In this study, the novel technique of Incompressible Smoothed Particle Hydrodynamics (ISPH) with shifting (Lind et al., J. Comput. Phys., 231(4):1499-1523, 2012), is extended beyond the state-of-the-art to model non-Newtonian and multi-phase flows. The method is used to investigate important problems of both environmental and industrial interest. The proposed methodology is based on a recent ISPH algorithm with shifting with the introduction of an appropriate stress formulation. The new method is validated both for Newtonian and non-Newtonian fluids, in closed-channel and free-surface flows. Applications in complex moulding flows are conducted and compared to previously published results. Validation includes comparison with other computational techniques such as weakly compressible SPH (WCSPH) and the Control Volume Finite Element method. Importantly, the proposed method offers improved pressure results over state-of-the-art WCSPH methods, while retaining accurate prediction of the flow patterns. Having validated the single-phase non-Newtonian ISPH algorithm, this develops a new extension to multi-phase flows. The method is applied to both Newtonian/Newtonian and Newtonian/non-Newtonian problems. Validations against a novel semi-analytical solution of a two-phase Poiseuille Newtonian/non-Newtonian flow, the Rayleigh-Taylor instability, and a submarine landslide are considered. It is shown that the proposed method can offer improvements in the description of interfaces and in the prediction of the flow fields of demanding multi-phase flows with both environmental and industrial application. Finally, the Lituya Bay landslide and tsunami is examined. The problem is approached initially on the real length-scales and compared with state-of-the-art computational techniques. Moreover, a detailed investigation is carried out aiming at the full reproduction of the experimental findings. With the introduction of a k-ε turbulence model, a simple saturation model and correct experimental initial conditions, significant improvements over the state-of-the-art are shown, managing an accurate representation of both the landslide as well as the wave run-up. The computational method proposed in this thesis is an entirely novel ISPH algorithm capable of modelling highly deforming non-Newtonian and multi-phase flows, and in many cases shows improved accuracy and experimental agreement compared with the current state-of-the-art WCSPH and ISPH methodologies. The variety of problems examined in this work show that the proposed method is robust and can be applied to a wide range of applications with potentially high societal and economical impact.

[pt] O presente trabalho apresenta uma generalização do teorema de Castigliano para a análise quase-estática de treliças inelásticas com dano (elasto-plásticas e elasto-viscoplásticas). É desenvolvida uma formulação abstrata geral para o problema considerando-se qualquer tipo de teoria constitutiva com variáveis internas. Uma técnica de aproximação numérica é apresentada, com base na decomposição aditiva do operador, e um algoritmo de solução é proposto. Finalmente a teoria proposta é testada simulando-se a ruptura de treliças metálicas submetidas a carregamentos monótonos e cíclicos (fadiga). / [en] The present work is concerned with an extension of the Castigliano s theorem to the case of inelastic damageable trusses (elasto-plastic and elasto-viscoplastic behavior). A general formulation that takes into account any kind of constitutive theory with internal variables is presented. A numerical technique, based on the operator splitting method, for approximating the resulting equations is proposed. Finally, the proposed theory is checked through examples concerning cyclic and monotone loadings in metallic trusses.

Made available in DSpace on 2014-10-09T12:50:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:42Z (GMT). No. of bitstreams: 1 00768.pdf: 4150056 bytes, checksum: 8e8c0f1f3b65b77306c6aeb1ee8f3508 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Fisica, Universidade de Sao Paulo - IF/USP

Made available in DSpace on 2014-10-09T12:45:56Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:42Z (GMT). No. of bitstreams: 1 07541.pdf: 9270192 bytes, checksum: 625d1a8ce146718eee35be24d9a360a3 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP