Este trabalho trata da formulação do método dos elementos de contorno para a análise não linear de pavimentos de concreto armado. A teoria utilizada é a de Reissner, que mostrou-se eficiente tanto para placas esbeltas quanto para as moderadamente espessas. Considera-se a ocorrência de cargas concentradas, distribuídas em sub-regiões da placa e em linha. Admite-se também a possibilidade de um campo de momentos iniciais, que viabiliza o estudo da não linearidade física nos problemas. Foram utilizados campos de momentos iniciais aplicados apenas em pontos internos ao domínio. As integrais que envolvem as células de domínio foram modificadas, eliminando-se os núcleos complexos e as aproximações através de séries. Foi desenvolvida uma formulação para a análise de placas vinculadas a estruturas quaisquer em seu domínio, com o uso de cargas aplicadas incógnitas atuando como enrijecedores. O acoplamento MEC/MEF foi empregado utilizando-se modelos simples, porém robustos. O sistema de equações algébricas foi otimizado com a utilização da técnica dos mínimos quadrados. O concreto foi modelado adotando-se o modelo de dano de Mazars; para as armaduras um modelo elastoplástico uniaxial com endurecimento isótropo. A análise não linear do problema é efetuada utilizando-se procedimento incremental-iterativo. São apresentados alguns exemplos simples que mostram a precisão da técnica usada. / This work refers to the formulation of the boundary element method for non-linear analysis of building floor structures. The plate bending theory adopted to develop the work wad due to Reissner, which has demonstrated to be efficient for thick, moderated thick and thin plates. The kinds of load applied on the plate medium surface have been taken into account: concentrated loading, distributed over sub-domains; distributed along internal lines. The presence of initial moment fields convenient to model temperature effects and to be used to build up non-linear solutions has also been considered in the formulation. The domain integrals containing complex kernels to take into account the initial moment field influences were modified by introducing their primitive functions, avoiding therefore using series expansions. To integrate the initial moments fields only approximations based on internal nodal points were used. The resulting cell integrals have been transformed to the cell boundary which results into regular integral only. A boundary element formulation to treat structural system defined by combining plates with other structural element was developed, using interface force as unknowns. The BEM/FEM coupling developed to treat this case is simple but robust; only displacements have been coupled avoiding important singularities that may happen when coupling rotations. The resulting system of algebraic equations has been regularized by using the least square method. The concrete material was modeled by using the Mazar\'s damage model, while the steel reinforcement was assumed to behave as elastoplastic material with isotropic hardening. Finally, some examples are shown to illustrate the accuracy of the presented formulation and the numerical schemes proposed in this work.

Este trabalho apresenta estudos referentes à rigidez de pilares em análises de segunda ordem. É discutida a questão dos parâmetros necessários para definir o comportamento reológico de peças de concreto armado e também são expostos os fenômenos de instabilidade das estruturas. Para o fornecimento de dados de rigidez para análises não-lineares, utilizam-se relações momento-normal-rigidez secante. Para isto, através da linearização das relações momento-curvatura, são construídos ábacos de curvas de interação, acopladas a valores de rigidez secante adimensionais, para seções retangulares, circulares e vazadas. Com a finalidade de demonstrar a aplicabilidade, apresentam-se exemplos de utilização desses ábacos para dimensionamento e verificação de pilares. Nestes exemplos a não-linearidade geométrica é considerada através do processo P-delta ou pelos processos simplificados como o do Pilar-Padrão e do Pilar-Padrão Melhorado, de acordo com a Norma Brasileira NBR 6118:2003. A não-linearidade física é considerada pelos ábacos de curvas de interação momento-normal-rigidez secante adimensionais ou pela expressão aproximada da rigidez secante. Além disso, são expostos métodos simplificados de cálculo adotados pelo boletim 16 da FIB e pelo Eurocode-2 para consideração da não-linearidade e comparados com a Norma Brasileira. / This work presents studies about the stiffness of columns in second order analysis. It is discussed the issue about the necessary parameters to define the rheological behavior of reinforced concrete pieces and it is also exposed the occurrences of structure instability. It is used relations of secant normal-stiffness-moment for the specification of stiffness data used in non-linear analysis. In this case, through the linearity of curvature-moment relations, curvature interaction diagrams are formed and incorporated to secant not dimensional stiffness values for rectangular, circular and hollow sections. With the objective to demonstrate its application, it is presented examples of use for the diagrams in column design and verification. In these examples the geometrical non-linearity is considered through the P-delta process or through the simplified processes like the Standard-Column and the Improved-Standard-Column, in accordance with the Brazilian Standard NBR 6118:2003. The physical non-linearity is considered through the diagrams of secant normal-stiffness-moment interactions or through the approximate identification of secant stiffness. In addition, it is shown the simplified calculation methods used by FIB Journal 16 and by Eurocode-2 for consideration of the non-linearity and comparison with the Brazilian Standard.

The emergence of new communication standards has put a key challenge for semiconductor industry to develop RF devices that can handle high power and high data rates simultaneously. The RF devices play a key role in the design of power amplifiers (PAs), which is considered as a heart of base-station. From economical point of view, a single wideband RF power module is more desirable rather than multiple narrowband PAs especially for multi-band and multi-mode operation. Therefore, device modeling has now become much more crucial for such applications. In order to reduce the device design cycle time, the researchers also heavily rely on computer aided design (CAD) tools. With improvement in CAD technology the model extraction has become more accurate and device physical structure optimization can be carried out with less number of iterations. LDMOS devices have been dominating in the communication field since last decade and are still widely used for PA design and development. This thesis deals with the optimization of RFLDMOS transistor and its evaluation in different PA classes, such as linear, switching, wideband and multi-band applications. For accurate evaluation of RF-LDMOS transistor parameters, some techniques are also developed in technology CAD (TCAD) using large signal time domain computational load-pull (CLP) methods. Initially the RF-LDMOS is studied in TCAD for the improved RF performance. The physical intrinsic structure of RF-LDMOS is provided by Infenion Technologies AG. A reduced surface field (RESURF) of low-doped drain (LDD) region is considered in detail because it plays an important role in RF-LDMOS devices to obtain high breakdown voltage (BVDS). But on the other hand, it also reduces the RF performance due to high on-resistance (Ron). The excess interface state charges at the RESURF region are introduced to reduce the Ron, which not only increases the dc drain current, but also improve the RF performance in terms of power, gain and efficiency. The important achievement is the enhancement in operating frequency up to 4 GHz. In LDD region, the effect of excess interface charges at the RESURF is also compared with dual implanted-layer of p-type and n-type. The comparison revealed that the former provides 43 % reduction in Ron with BVDS of 70 V, while the later provides 26 % reduction in Ron together with BVDS of 64 - 68 V. In the second part of my research work, computational load pull (CLP) simulation technique is used in TCAD to extract the impedances of RF-LDMOS at different frequencies under large signal operation. Flexible matching is an issue in the design of broadband or multi-band PAs. Optimum impedance of RF-LDMOS is extracted at operating frequencies of 1, 2 and 2.5 GHz in class AB PA. After this, CLP simulation technique is further developed in TCAD to study the non-linear behavior of RF devices. Through modified CLP technique, non-linear effects inside the transistor structure are studied by conventional two-tone RF signals in time domain. This is helpful to detect and understand the phenomena, which can be resolved to improve the device performance. The third order inter-modulation distortion (IMD3) of RF- LDMOS was observed at different power levels. The IMD3 of −22 dBc is obtained at 1-dB compression point (P1-dB), while at 10 dB back off the value increases to −36 dBc. These results were also verified experimentally by fabricating a linear PA. Similarly, CLP technique is developed further for the analysis of RF devices in high efficiency operation by investigating the odd harmonic effects for the design of class-F PA. RF-LDMOS can provide a power added efficiency (PAE) of 81.2 % in class-F PA at 1 GHz in TCAD simulations. The results are verified by design and fabrication of class-F PA using large signal model of the similar device in ADS. In fabrication, a PAE of 76 % is achieved.

The research described in this dissertation undertakes a computational study of wave motion due to ground excitation in layered soil media. Adjustments of soil properties consistent with the level of deformation is applied using an equivalent linear approach. The finite element method provides the basis of the numerical procedure for soil-structure system response calculation in conjunction with a first-order perturbation scheme. Available experimental data are employed for shear-modulus and damping adjustments. The findings of the research are expected to lead to efficient calculation of structural response to earthquake ground motion. / text

Αντικείμενο της παρούσας εργασίας είναι η ανάλυση κτιρίων από φέρουσα τοιχοποιία σύμφωνα με ανελαστικό προσομοίωμα βλάβης στοιχείων τοιχοποιίας. Το προσομοίωμα βασίζεται στην θεωρία βλάβης συνεχούς μέσου και χρησιμοποιεί εννέα δείκτες βλάβης για την περιγραφή της μη γραμμικής συμπεριφοράς. Οι δείκτες βλάβης λαμβάνουν τιμές από 0 έως 1 και οι συναρτήσεις για τον υπολογισμό τους εμπεριέχουν τις εξισώσεις επιφάνειας οριακής αστοχίας κατά τα κριτήρια Rankine και Hill, ώστε να ληφθεί υπόψη η αλληλεπίδραση των τάσεων. Η εφαρμογή του προσομοιώματος πραγματοποιείται σε υπό κλίμακα κτίρια τοιχοποιίας, που αποτέλεσαν πειραματικά δοκίμια των σεισμικών τραπεζών LEE (Ελλάδα) και ISMES (Ιταλία), στα πλαίσια ερευνητικού προγράμματος. Αναλύονται τέσσερα κτίρια με ανελαστική ανάλυση χρονοϊστορίας: μία λιθοδομή, μία οπτοπλινθοδομή, μία ενισχυμένη λιθοδομή με τοπικούς μανδύες σκυροδέματος και μία ενισχυμένη οπτοπλινθοδομή με ελκυστήρες και κατακόρυφες μεταλλικές δοκούς. Βασική επιδίωξη είναι η ποιοτική σύγκριση των βλαβών που προβλέπει το προσομοίωμα, με τις πραγματικές αστοχίες των πειραματικών δοκιμίων. Τα αποτελέσματα των αναλύσεων δείχνουν πως δεν υπάρχει πάντα τέλεια αντιστοίχηση μεταξύ των τάσεων, οι οποίες αποτιμώνται βάσει των μονοαξονικών αντοχών και των αντίστοιχων δεικτών βλάβης, καθώς ο δείκτης βλάβης έχει κατά κύριο λόγο μαθηματικό νόημα, εκφράζει τον ρυθμό ανάπτυξης της βλάβης και στους υπολογισμούς εισάγεται η αντοχή όπως προκύπτει από την επιφάνεια οριακής αστοχίας. Από τα τέσσερα κτίρια που αναλύθηκαν κρίνεται πως για τα δύο από αυτά: τη λιθοδομή και την ενισχυμένη οπτοπλινθοδομή, προβλέπονται αστοχίες που συμβαδίζουν με τα διαθέσιμα πειραματικά στοιχεία. Η ανάλυση της οπτοπλινθοδομής προβλέπει βλάβες μικρότερου βαθμού από αυτές που προέκυψαν στα πειραματικά δοκίμια, ενώ για την ενισχυμένη λιθοδομή αν και παρουσιάζονται ρεαλιστικά αποτελέσματα, η σύγκριση είναι δυσχερής λόγω έλλειψης των πειραματικών αποτελεσμάτων. / In this thesis, a non – linear damage model for masonry is examined. The model is based on the continuous damage theory and nine indices are used to describe non – linear behavior of masonry. The damage index can assume values between 0 (undamaged state) and 1 (rupture), and in three – dimensional dynamic application takes into accent the influence of strains with the damage boundary surface formulated by Rankine and Hill criteria. The model has been implemented in a three – dimensional finite element program capable of performing static and dynamic inelastic analyses. The simulations of four masonry experimental models of shaking table in ISMES (Italy) and LEE (Greece) facilities carried out: a stone masonry, a brick masonry, a stone masonry partial strengthened by concrete jacket and a brick masonry strengthened by horizontal tendons and vertical steel beams placed at the corners of the building. Aim of the thesis is to compare the numerical results with the experimental data. The numerical results show that there not always evident convergence between the results of damage indices and the uniaxial strain for two reasons: first, the damage index takes into account the influence of strains and second, because the damage index represents the rate of damage development and has basically mathematical meaning. The damage model presents good response in representing the non linear behavior of stone masonry and strengthened brick masonry buildings. The numerical results for the brick masonry building maintains low degree of damage in order to experimental results and the analysis of strengthened stone masonry building gives realistic results of damage but very few experimental data are available for comparison purposes.

Disertacijoje sprendžiama telekomunikacinių stiebų efektyvumo problema. Tyrimo objektas – statiškai apkrauti naujos konstrukcijos stiebai su kombinuotomis atotampomis. Darbe išanalizuota šiuolaikinių stiebų konstrukcinės formos ir skaičiavimo metodai. Nagrinėjama sukurta stiebo su kombinuotomis atotampomis konstrukcija, kurioje vietoj įprastųjų siūloma taikyti kombinuotas atotampas. Disertacijoje šiems stiebams skaičiuoti pateikta inžinerinė skaičiavimo metodika. Pateikti naujo stiebo, veikiamo statinių apkrovų, elgsenos analizės skaitinių ir eksperimentinių laboratorinių tyrimų rezultatai. Stiebo su kombinuotomis atotampomis kamieno lenkiamiesiems momentams reguliuoti darbe siūloma taikyti parengtą stiebų komponavimo metodiką. Šių stiebų efektyvumui nustatyti pateikti gretinamieji tyrimai su įprastos sandaros stiebais. Disertaciją sudaro bendroji darbo charakteristika, 5 skyriai, pagrindiniai darbo rezultatai ir išvados, literatūros sąrašas. / Тhe dissertation deals with the problem of telecommunication masts efficiency. The subject of research – masts of a new structure with combined guys under static loads. The study deals with constructive forms and analysis methods of up-to-date masts. It analyses into a created structure of the mast, wherein it is suggested to apply combine guys instead of the ordinary ones. Engineering guyed masts with combined guys static analysis method is given this research. The numerical and experimental laboratory assay of a new mast under static loads behaviour is given. It is proposed in the study to apply a worked out composing method of masts with combined guys to control the bending moments of shaft. Compared research results are given to measure efficiency of these masts against masts of an ordinary structure. The dissertation includes a general characteristic of study, five chapters, main results and conclusions, list of references.

Тhe dissertation deals with the problem of telecommunication masts efficiency. The subject of research – masts of a new structure with combined guys under static loads. The study deals with constructive forms and analysis methods of up-to-date masts. It analyses into a created structure of the mast, wherein it is suggested to apply combine guys instead of the ordinary ones. Engineering guyed masts with combined guys static analysis method is given this research. The numerical and experimental laboratory assay of a new mast under static loads behaviour is given. It is proposed in the study to apply a worked out composing method of masts with combined guys to control the bending moments of shaft. Compared research results are given to measure efficiency of these masts against masts of an ordinary structure. The dissertation includes a general characteristic of study, five chapters, main results and conclusions, list of references. / Disertacijoje sprendžiama telekomunikacinių stiebų efektyvumo problema. Tyrimo objektas – statiškai apkrauti naujos konstrukcijos stiebai su kombinuotomis atotampomis. Darbe išanalizuota šiuolaikinių stiebų konstrukcinės formos ir skaičiavimo metodai. Nagrinėjama sukurta stiebo su kombinuotomis atotampomis konstrukcija, kurioje vietoj įprastųjų siūloma taikyti kombinuotas atotampas. Disertacijoje šiems stiebams skaičiuoti pateikta inžinerinė skaičiavimo metodika. Pateikti naujo stiebo, veikiamo statinių apkrovų, elgsenos analizės skaitinių ir eksperimentinių laboratorinių tyrimų rezultatai. Stiebo su kombinuotomis atotampomis kamieno lenkiamiesiems momentams reguliuoti darbe siūloma taikyti parengtą stiebų komponavimo metodiką. Šių stiebų efektyvumui nustatyti pateikti gretinamieji tyrimai su įprastos sandaros stiebais. Disertaciją sudaro bendroji darbo charakteristika, 5 skyriai, pagrindiniai darbo rezultatai ir išvados, literatūros sąrašas.

Deterioration of concrete bridge decks has become a serious problem in the past few decades. Fortunately, non-corrosive, light-weight Fiber Reinforced Polymer (FRP) material provides an excellent alternative. More than 117 bridges in the USA have been built or repaired with FRP. In Canada, no FRP bridge deck has been used in the field, yet. However, Wardrop Engineering Inc., Faroex Ltd., and ISIS Canada have successfully designed, manufactured, and patented the filament-wound Glass Fiber Reinforced Polymer (GFRP) bridge deck. Since there is no design code for FRP bridge decks, a finite element method, labeled “L&D”, is proposed in this thesis to help bridge engineers better understand the structural behavior of FRP bridge decks. The L&D method is validated by comparing the analysis results with the experimental results of three filament-wound GFRP bridge decks. This L&D method is also applicable for analyzing FRP bridge decks manufactured by other processes.

Deterioration of concrete bridge decks has become a serious problem in the past few decades. Fortunately, non-corrosive, light-weight Fiber Reinforced Polymer (FRP) material provides an excellent alternative. More than 117 bridges in the USA have been built or repaired with FRP. In Canada, no FRP bridge deck has been used in the field, yet. However, Wardrop Engineering Inc., Faroex Ltd., and ISIS Canada have successfully designed, manufactured, and patented the filament-wound Glass Fiber Reinforced Polymer (GFRP) bridge deck. Since there is no design code for FRP bridge decks, a finite element method, labeled “L&D”, is proposed in this thesis to help bridge engineers better understand the structural behavior of FRP bridge decks. The L&D method is validated by comparing the analysis results with the experimental results of three filament-wound GFRP bridge decks. This L&D method is also applicable for analyzing FRP bridge decks manufactured by other processes.

Lajes nervuradas modeladas computacionalmente são geralmente analisadas por metodologias simplificadas, tanto para a geometria da seção (convertendo em lajes maciças ou grelhas) como para as propriedades mecânicas dos materiais (regime elástico-linear). Estes estudos teóricos apresentam grandes diferenças quando comparados com ensaios experimentais, mesmo para baixos níveis de carregamento. Isto se deve principalmente pela não consideração da excentricidade entre os eixos da nervura e da capa, como também à simplificação do comportamento mecânico do concreto à tração. Modelos numéricos chamados realísticos consideram o efeito da excentricidade entre os eixos da capa e nervura da seção transversal. Pode-se, ainda, introduzir a não-linearidade física do concreto armado nestes modelos, obtendo resultados mais próximos do real. O objetivo deste trabalho é estabelecer um modelo numérico realístico, para a seção típica de laje nervurada, atendendo às indicações descritas acima. Para a consideração da excentricidade entre os eixos da capa e nervura empregam-se elementos de casca, em posição horizontal para a capa e vertical para a nervura. A não-linearidade física do concreto à tração é representada através do modelo de fissuração distribuída proposto por D’AVILA (2003). Para as análises não-lineares empregou-se o programa computacional de elementos finitos SAP2000 versão 16, onde os elementos de casca permitem discretizar o concreto armado em camadas, ao longo da espessura. Um bom desempenho do modelo numérico proposto foi verificado pela validação deste a partir de modelos experimentais, assim como da análise numérica de outros autores. Realizaram-se, por último, análises de algumas lajes nervuradas com solicitações de carregamentos excessivos, a fim de prever seus desempenhos frente a estados limites de flexão. Os resultados obtidos nestas análises mostraram, também, um bom desempenho do modelo proposto. / Waffle slab structures simulated by computational models are generally analyzed by simplified methods, both for section geometry (converting into solid slabs) and the material mechanical properties (linear elastic regime). The results obtained by such theoretical studies show large differences when compared to experimental tests, even at low loading levels. This is mainly due to non-consideration of the eccentricity between the rib and cover axes and simplification of the concrete tensile strength mechanical behavior. The so called realistic numerical models consider the effect of eccentricity between the axes of hood and ribs of the cross section. One may also introduce physical nonlinearity of reinforced concrete in these models, obtaining results closer to real. The objective of this work is to establish a realistic numerical model for the typical section of a waffle slab, considering the physical nonlinearity of concrete and its collaboration between cracks, by the smeared crack model proposed by D' AVILA (2003). The computational finite element program SAP2000 version 16 is used for the non-linear analysis. The shell element discretization enabled the heterogeneous characteristics of reinforced concrete to be considered through layers along the thickness. The numerical model was validated based on the analysis of experimentally tested slabs. Finally, some waffle slabs were numerically analyzed under a uniformly distributed and incrementally growing load. The proposed model was able to predict their overall behavior and some local aspects could also be observed.