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INELASTIC SEISMIC RESPONSE ANALYSIS OF ECCENTRICALLY LOADED STEEL BRIDGE PIERSKASAI, Akira, 葛西, 昭, LIU, Qingyun, 劉, 青芸, USAMI, Tsutomu, 宇佐美, 勉 07 1900 (has links)
No description available.
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Nonlinear Dynamic Analysis of Structures with Hyperelastic DevicesSaunders, Richard A. 25 May 2004 (has links)
This thesis presents the results of an investigation of a multiple degree of freedom (MDOF) structure with hyperelastic bracing using nonlinear and incremental dynamic analysis. New analytical software is implemented in the investigation of the structure, and the study seeks to investigate the effectiveness of hyperelastic bracing as a seismic protection device. Hyperelastic braces incorporate a new idea of a nonlinear elastic material that gains stiffness as the brace deforms. Structural behaviors of particular concern for an MDOF frame are stability, residual displacement, base shear, and dispersion. The structure is analyzed under two ground motion records of varying content, and for two separate P-Delta cases of varying severity. Two sets of hyperelastic braces are investigated for their influence under the two ground motions and two P-Delta cases. Each scenario is analyzed using nonlinear dynamic analyses to investigate the response histories, and Incremental Dynamic Analysis (IDA) to investigate dispersion and the behavior of specific response measures as ground motion intensity increases. IDA curves are created for interstory drift and base shear for comparison between the two response measures. The research shows that the inclusion of hyperelastic braces in the MDOF frame improves the overall stability of the structure and reduces the amount of dispersion and residual displacement. The hyperelastic braces are shown to give positive performance characteristics while not detrimentally increasing system forces under regular service loads. The results highlight the benefit of the unique stiffening properties of hyperelastic braces as a seismic protection device. / Master of Science
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Damage Development in Static and Dynamic Deformations of Fiber-Reinforced Composite PlatesHassan, Noha Mohamed 27 December 2005 (has links)
A three-dimensional finite element code to analyze coupled thermomechanical deformations of composites has been developed. It incorporates geometric nonlinearities, delamination between adjoining layers, and damage due to fiber breakage, fiber/matrix debonding, and matrix cracking. The three damage modes are modeled using the theory of internal variables and the delamination by postulating a failure envelope in terms of the transverse stresses; the damage degrades elastic moduli. The delamination of adjoining layers is simulated by the nodal release technique. Coupled nonlinear partial differential equations governing deformations of a composite, and the pertinent initial and boundary conditions are first reduced to coupled ordinary differential equations (ODEs) by the Galerkin method. These are integrated with respect to time with the Livermore solver for ODEs. After each time step, the damage in an element is computed, and material properties modified. The code has been used to analyze several static and transient problems; computed results have been found to compare well with the corresponding test results. The effect of various factors such as the fiber orientation, ply stacking sequence, and laminate thickness on composite's resistance to shock loads induced by underwater explosions has been delineated. / Ph. D.
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Stability of precast prestressed concrete bridge girders considering imperfections and thermal effectsHurff, Jonathan B. 30 June 2010 (has links)
The spans of precast prestressed concrete bridge girders have become longer to provide more economical and safer transportation structures. As the spans have increased, so has the depth of the girders which in turn have increased the slenderness of the girders. Slenderness in a beam or girder would increase the likelihood that a stability failure would occur. Stability failures could pose a danger to construction personnel due to the sudden nature in which a stability failure would occur. Furthermore, stability failures of prestressed concrete girders during construction would cause a detrimental economic impact due to the costs associated with the failure of the girder, the ensuing construction delays, damage to construction equipment and potential closures to highways over which the bridge was being constructed.
An experimental and analytical study was performed to determine the stability behavior of prestressed concrete beams. Two stability phenomenons were investigated: (1) lateral-torsional buckling and (2) global stability. An emphasis was placed on the effects of initial imperfections on the stability behavior; the effect elastomeric bearing pads and support rotational stiffness was investigated. The experimental study involved testing six rectangular prestressed concrete beams for lateral-torsional buckling, a PCI BT-54 for thermal deformations and the same PCI BT-54 for global stability. The 32-ft. long rectangular beams were 4-in. wide and 40-in. deep. The PCI BT-54 had a 100-ft. long span.
A material and geometric nonlinear, incremental load analysis was performed on the six rectangular beams. The nonlinear analyses matched the experimental load versus lateral displacement and load versus rotation behavior, and the analysis predicted the experimental maximum load within an error of 2%. The nonlinear analysis was extrapolated to several different initial imperfection conditions to parametrically study the effect of initial lateral displacement and initial rotation on the inelastic lateral-torsional buckling load. A simplified expression for lateral-torsional stability of beams with initial imperfections was developed. The data from the parametric study were used to develop reduction parameters for both initial sweep and initial rotation.
The rollover stability behavior of the PCI BT-54 was investigated experimentally, and it was found that support end rotations and the elastomeric bearing pads had an adverse effect on the global stability. The nonlinear analysis was employed with the addition of a bearing pad model. It was found that the behavior was sensitive to the bearing pad stiffness properties and the assumption of uniform bearing. From the research, it was apparent that rollover stability was the controlling stability phenomenon for precast prestressed concrete bridge girders, not lateral-torsional buckling.
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[en] UNIFORMLY PROBABLE DESIGN RESPONSE SPECTRUM FOR INELASTIC SECONDARY SYSTEMS / [pt] ESPECTRO DE RESPOSTA DE PROJETO UNIFORMEMENTE PROVÁVEL PARA SISTEMAS SECUNDÁRIOS INELÁSTICOSREGINA AUGUSTA CAMPOS SAMPAIO 15 December 2003 (has links)
[pt] Estuda-se a consideração de comportamento inelástico do
material na geração de espectros de resposta de projeto.
Para tanto, trabalha-se sobre um sistema secundário
simplificado acoplado a um pórtico de cinco andares com
características dinâmicas ajustadas para modelar um sistema
principal real, de uma usina nuclear. Faz-se um estudo
paramétrico sobre estes sistemas acoplados onde são
variados os parâmetros: fator de escoamento, a intensidade
da excitação e o nível de amortecimento. É proposto um
fator de dutilidade global formulado em termos de trabalho
externo realizado sobre o sistema secundário. São obtidos
espectros de dutilidade e de resposta. A análise de tais
espectros fornece informações sobre o desempenho do sistema
secundário e seus suportes e conclui por fatores de
transposição entre os espectros elástico e inelástico.
Propõe-se metodologia para obtenção de espectros de
resposta elásticos e inelásticos que levam em conta o
acoplamento entre os sistemas principal e secundário, o
movimento relativo dos suportes e o compromisso
probabilístico entre as ordenadas do espectro e a
sismicidade da região expressa em termos de uma função
densidade de espectro de potência objetivo para a
aceleração do terreno. Um exemplo de obtenção de espectros
de resposta acoplada de projeto uniformemente provável
inelástico é apresentado. / [en] The authors concern includes two main points in the subject
of design response spectra generation for secondary systems
in nuclear power plant structures: the consideration of
inelastic behavior in the secondary systems materials and
the production of uniformly probable design response
spectra. One works with a previously developed secondary
system model attached to primary structure model tuned to
the frequency range of a nuclear power plant building.
A global ductility factor is formulated relating the
plastic to the overall work done by the seismic external
forces on the secondary system. This factor together with a
particular definition of the yielding factor allows one to
determine elastic to inelastic spectrum transpose factors.
A methodology is proposed to generate uniformly probable
coupled response spectra for multiply supported inelastic
secondary systems. The seismic excitation is prescribed by
a target power spectrum density function of the ground
acceleration and an internal pressure condition is added to
the seismic action. Examples illustrate the application of
this proposed methodology.
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Μελέτη ανελαστικής συμπεριφοράς του γεφυριού της Κόνιτσας με χρήση ανελαστικού προσομοιώματος για τοιχοποιία και εφαρμογή μεθόδων ενίσχυσηςΚορομπίλιας, Δημήτριος 26 February 2015 (has links)
Η διατριβή μπορεί να χωριστεί σε δύο μέρη. Το πρώτο μέρος αφορά την παρουσίαση του θεωρητικού υποβάθρου του μαθηματικού προσομοιώματος που χρησιμοποιήθηκε για να περιγράψει τη βλάβη που μπορεί να εμφανιστεί σε μια κατασκευή έπειτα από την επιβολή δυναμικής ή στατικής φόρτισης. Το προσομοίωμα αυτό χρησιμοποιήθηκε στην παρούσα διατριβή για την ανάλυση της γέφυρας της Κόνιτσας και γι’ αυτό το λόγο κρίθηκε απαραίτητη η αναφορά στο θεωρητικό υπόβαθρο, πάνω στο οποίο στηρίζεται. Το δεύτερο μέρος της διατριβής αφορά τη σεισμική ανάλυση της γέφυρας της Κόνιτσας, την αξιολόγηση των αποτελεσμάτων και τη διαδικασία ενίσχυσής της, καθώς και τη μετέπειτα σύγκριση των αποτελεσμάτων.
Έτσι λοιπόν, στο πρώτο κεφάλαιο γίνεται αρχικά μια ιστορική ανασκόπηση της τοιχοποιίας ενώ στην συνέχεια γίνεται αναφορά τόσο στις κατηγορίες της όσο και στην τοιχοποιία ως υλικό δόμησης. Επιπλέον, γίνεται μία σύντομη περιγραφή των μηχανικών ιδιοτήτων της τοιχοποιίας. Τέλος, παρουσιάζονται σύντομα οι θεμελιώδεις παραδοχές και οι στόχοι του προσομοιώματος που χρησιμοποιήθηκε και εφαρμόστηκε στην παρούσα εργασία.
Το δεύτερο κεφάλαιο, αποτελεί το εισαγωγικό μέρος στο οποίο παρουσιάζεται λεπτομερέστερα τα στοιχεία μηχανικής της τοιχοποιίας. Αρχικά, γίνεται αναφορά στην ταξινόμηση της τοιχοποιίας, ως προς τους τρόπους δόμησης, ενώ στην συνέχεια αναλύονται οι μηχανικές της ιδιότητες. Στις υποπαραγράφους του δευτέρου κεφαλαίου, αναλύεται δηλαδή η αντοχή της τοιχοποιίας σε μονοαξονική θλίψη, σε πολυαξονική θλίψη, η εφελκυστική αντοχή σε κάμψη, η διατμητική αντοχή καθώς και η αντοχή υπό τυχούσα επίπεδη καταπόνηση. Τέλος παρουσιάζονται τα ελαστικά χαρακτηριστικά της τοιχοποιίας ενώ περιγράφεται και η διαδικασία της ομογενοποίησης των συστατικών της τοιχοποιίας προκειμένου να αντιμετωπίζεται ως ένα ισοδύναμο ομογενές υλικό.
Στο τρίτο κεφάλαιο γίνεται σύντομη περιγραφή της θεωρίας βλάβης του συνεχούς μέσου και ο τρόπος που εισάγεται αυτή στο μαθηματικό προσομοίωμα που εφαρμόστηκε στο δεύτερο μέρος της διατριβής. Αρχικά, λοιπόν, γίνεται μια μηχανική αναπαράσταση της βλάβης και στη συνέχεια παρουσιάζεται το θεωρητικό υπόβαθρο της θεωρίας βλάβης στα ψαθυρά υλικά. Ακολουθεί μία σύντομη περιγραφή του δείκτη βλάβης και η διατύπωση των συναρτήσεών του, όπως αυτές διαμορφώθηκαν κατά την ανάπτυξη του μαθηματικού προσομοιώματος που εφαρμόστηκε στην εργασία, για μονοαξονική θλιπτική καταπόνηση, για μονοαξονική εφελκυστική καταπόνηση, για διατμητική καταπόνηση μετά ορθής τάσης, για επίπεδη εντατική κατάσταση και τέλος τη γενίκευση του για τριαξονική εντατική κατάσταση.
Στο τέταρτο κεφάλαιο περιγράφεται η επιφάνεια οριακής αντοχής. Αρχικά, δηλαδή, παρουσιάζονται συνοπτικά, και σύμφωνα με την βιβλιογραφία, οι μηχανισμοί αστοχίας της τοιχοποιίας καθώς και ο τρόπος υπολογισμού των τάσεων οριακής αντοχής. Στη συνέχεια διατυπώνονται οι μηχανισμοί αστοχίας της τοιχοποιίας υπό επίπεδη εντατική κατάσταση καθώς και ο γεωμετρικός προσδιορισμός της επιφάνειας οριακής αντοχής της τοιχοποιίας ενώ τέλος παρουσιάζονται οι σχέσεις που υπολογίζουν την οριακή αντοχή της τοιχοποιίας υπό συνθήκες τριαξονικής εντατικής κατάστασης.
Στο πέμπτο κεφάλαιο, παρουσιάζονται συνοπτικά οι μέθοδοι αποκατάστασης και ενίσχυσης κατασκευών από τοιχοποιία. Μετά από μία σύντομη βιβλιογραφική αναφορά για την τρωτότητα των κατασκευών από φέρουσα τοιχοποιία, των βλαβών υπό τη δράση στατικών και σεισμικών φορτίσεων, των βλαβών υπό τη δράση περιβαλλοντικών παραγόντων, των κριτηρίων και των αρχών επεμβάσεων επισκευής και ενίσχυσης και των τεχνικών επεμβάσεων επισκευής και ενίσχυσης, γίνεται μια περιγραφική αναφορά των ενισχύσεων τοιχοποιίας με μανδύα οπλισμένου σκυροδέματος και με προεντεταμένους ελκυστήρες, καθώς αυτοί οι μέθοδοι ενίσχυσης χρησιμοποιήθηκαν και για τη γέφυρα της Κόνιτσας στον Αώο ποταμό.
Στο έκτο κεφάλαιο, περιγράφεται συνοπτικά το λογισμικό που κάνει χρήση πεπερασμένων στοιχείων και επιλέχθηκε για την εφαρμογή του προσομοιώματος. Γίνεται αναφορά στις επιλογές ανάλυσης και τις δυνατότητες του προγράμματος αυτού καθώς και της δυνατότητας γραφικής απεικόνισης των αποτελεσμάτων που παράγει..
Στο έβδομο κεφάλαιο, παρουσιάζεται η κατασκευή που επιλέχθηκε προκειμένου να γίνει αριθμητική εφαρμογή του προσομοιώματος βλάβης. Αρχικά, περιγράφεται η γέφυρα της Κόνιτσας και γίνεται αναφορά των γεωμετρικών στοιχείων της. Έπειτα, παρουσιάζονται ορισμένα ιστορικά στοιχεία της γέφυρας. Στη συνέχεια, περιγράφεται ο τρόπος προσομοίωσης της γέφυρας με τη χρήση πεπερασμένων στοιχείων και αναφέρονται οι μηχανικές ιδιότητες των υλικών της. Επιπλέον, γίνεται αναφορά στις δυναμικές αναλύσεις χρονοϊστορίας που έγιναν τόσο για την αρχική κατάσταση της γέφυρας όσο και στις φάσεις ενίσχυσης με τη χρήση μανδύα οπλισμένου σκυροδέματος ή με τη χρήση προεντεταμένων ελκυστήρων. Τέλος, αναλύονται οι διαδικασίες ενίσχυσης της γέφυρας είτε με μανδύα οπλισμένου σκυροδέματος είτε με προεντεταμένους ελκυστήρες.
Στο όγδοο κεφάλαιο, παρουσιάζονται τα αποτελέσματα των αναλύσεων της γέφυρας τόσο για την αρχική κατάστασή της, δηλαδή της μη ενισχυμένης περίπτωσης, όσο και για τις δύο περιπτώσεις στις οποίες η γέφυρα έχει ενισχυθεί με μανδύα σκυροδέματος ή με προεντεταμένους ελκυστήρες.
Στο ένατο κεφάλαιο, παρουσιάζονται τα συμπεράσματα που προέκυψαν από τις αναλύσεις της γέφυρας τόσο για την αρχική της κατάσταση όσο και για τις ενισχυμένες περιπτώσεις. / The thesis can be divided into two parts. The first part deals with the presentation of the theoretical background of the mathematical model used to describe the damage that can occur in a construction upon a dynamic or static charge. The model was used in this thesis to analyze the bridge of Konitsa and for this reason the reference to the theoretical background was necessary, on which rests. The second part of the thesis concerns the seismic analysis of the bridge of Konitsa, evaluation of results and building processes and the subsequent comparison of results.
Thus, the first chapter is initially a historical overview of the masonry and then refer to both categories and masonry as building material. Moreover, there is a brief description of the mechanical properties of masonry. Finally, presented briefly the fundamental assumptions and objectives of the model used and applied in the present work.
The second chapter is the introductory part in which the masonry engineering data presented in more detail. Initially, reference is made to the classification of the masonry, for the construction of ways and then analyzed the mechanical properties. In sub-second chapter, that analyzes the strength of masonry in uniaxial compression, a multiaxial compressive, tensile bending strength, shear strength and durability under arbitrary stress levels. Finally presents the elastic characteristics of masonry and described the process of homogenization of the components of the masonry to be treated as an equivalent homogeneous material.
The third chapter is a brief description of the error theory of continuous medium and the way it is introduced in the mathematical model applied in the second part of the thesis. Initially, then, is a mechanical representation of the lesion and then presents the theoretical background of damage theory in brittle materials. Following is a brief description of the index lesion and the expression of functions, like those formed during the development of the mathematical model applied to work, uniaxial compressive stress for uniaxial tensile stress for shear stress after proper voltage for plane stress conditions and end generalization for triaxial stress state.
The fourth chapter describes the ultimate strength surface. Initially, ie, summarized, and according to the literature, the masonry failure mechanisms and the calculation of ultimate resistance trends. Then the masonry failure mechanisms are mentioned under plane stress conditions and the geometric definition of the ultimate strength of the masonry surface and finally presents the relations that calculate the ultimate strength of the masonry under conditions of triaxial stress condition.
In the fifth chapter summarizes the methods of recovery and strengthening masonry structures. After a brief reference for the vulnerability of masonry structures, damage under the action of static and seismic loads, damage under the action of environmental factors, the criteria and repair operations authorities and aid and technical assistance and repair operations, is a descriptive report of wall reinforcement with concrete jacket and prestressing tractors, as these payment methods used and the bridge of Konitsa Aoos River.
In the sixth chapter, summarized the software that makes use of finite element chosen for the implementation of the model. Refer to the analytical options and features of the program and the graphic display feature of the results produced ..
In the seventh chapter, the structure was chosen in order to make numerical implementation of the model fault. Initially, described the bridge of Konitsa and reference geometric details. Then are some historical elements of the bridge. Then describe how simulation of the bridge using finite element and are the mechanical properties of the materials. Furthermore, reference is made to the dynamic history analyzes conducted for both the initial state of the bridge and in the amplification stages using concrete jacket or using prestressed tractors. Finally, we analyze the bridge-building processes or concrete jacket or prestressing tractors.
In the eighth chapter presents the results of analyzes of the bridge both the initial condition, ie unamplified case, and for two cases in which the bridge has been reinforced with mantle concrete or prestressing tractors.
In the ninth chapter presents the conclusions drawn from the analysis of both the bridge in its original condition and for reinforced cases.
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鋼製補剛箱形断面橋脚の繰り返し弾塑性挙動に関する解析的研究葛, 漢彬, Ge, Hanbin, 宇佐美, 勉, Usami, Tsutomu, 高, 聖彬, Gao, Shengbin 03 1900 (has links)
No description available.
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[en] EFFECTS OF THE INTERNAL PRESSURE AND TEMPERATURE VARIATIONS ON SEISMIC RESPONSE SPECTRA OF TUBULAR SYSTEMS / [pt] A PRESSÃO INTERNA E A VARIAÇÃO DE TEMPERATURA NOS SISTEMAS DE TUBULAÇÃO E OS ESPECTROS DE RESPOSTA DE PROJETO PARA CARGAS SÍSMICASJAIR JOSE DOS SANTOS GOMES 11 July 2005 (has links)
[pt] A análise de estruturas de sistemas secundários sujeitos a
cargas sísmicas é um
assunto em aberto e especial no projeto de instalações
industriais. Dois pontos
particulares atraem a atenção dos especialistas no esforço
a caminho de um projeto
mais realista, abrangente e econômico: a interação das
propriedades dinâmicas entre os
sistemas principal e secundário e a quantidade de
dutilidade do sistema secundário que
pode ou deveria ser considerada no projeto. Está muito
evidente nesse estágio que a
decisão do projetista tem de ser bem assessorada porque
dependendo das circunstâncias
os resultados finais podem mostrar muitas surpresas. O
contexto das experiências
nesse assunto, na PUC-Rio, inclui uma série de
iniciativas. Entre elas, se pode dar
especial menção às seguintes: o estudo e proposta de uma
metodologia para
desenvolver um espectro de resposta acoplada (Valverde,
1998); o desenvolvimento de
um modelo de sistema secundário simplificado: com vários
graus de liberdade, linearelástico,
formado por elementos tubulares, conexões e suportes com
molas (Castañaga,
1998); a introdução do efeito inelástico nos elementos
tubulares e suportes do sistema
secundário simplificado e definição de um fator de
dutilidade global do sistema para
relacionar, qualitativa e quantitativamente, o espectro de
resposta acoplada do sistema
secundário simplificado, sob comportamento elástico e
inelástico (Sampaio, 2003).
Agora, um outro avanço é incorporado, com o presente
estudo, o da influência de
cargas estáticas nos elementos devidas à pressão interna e
variação de temperatura,
nessas relações do espectro de resposta elástica e
inelástica. Também é feita uma
comparação dos espectros de resposta elástica e inelástica
do sistema secundário
acoplado e não acoplado. Espectros médios aproximados para
a resposta inelástica
acoplada do sistema secundário simplificado são também
propostos. / [en] The analysis of secondary structure systems to seismic
loads is a special and open
subject in the design of industrial installations. Two
particular points attract specialist
attention and effort on the way of a more realist,
comprehensive and economical
design: the dynamical properties interaction between the
secondary and principal
systems and the amount of the secondary system ductility
which can or should be
considered in the design. It is very clear at this stage
that the designer decision has to be
well advised because depending on circumstances the final
results may show very
surprising. The context of experiences on this subject, at
PUC-Rio, includes a series of
initiatives. Among them, one may to give special mention
to the following: the study
and proposal of a methodology to develop a coupled floor
response spectrum
(Valverde, 1998); the development of a simplified
secondary system model: multidegree,
linear-elastic, tubular elements and connexions and spring
supports (Castañaga,
1998); the introduction of inelastic action in the tubular
elements and supports of the
simplified secondary system and the definition of a system
overall ductility factor to
relate, qualitative and quantitatively, the simplified
secondary system coupled response
spectrum under elastic and inelastic behavior (Sampaio,
2003). Now, another
advancement is enhanced with this study on the influence
of element static loads due to
internal pressure and temperature variation on these
elastic and inelastic response
spectrum relationships. Comparison also is made into
coupled and uncoupled
secondary system elastic and inelastic response spectra.
Approximated medium
response spectra for the inelastic coupled response of a
simplified secondary system are
also proposed.
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