Αντικείμενο του παρόντος άρθρου αποτελεί η ανάλυση της συμπεριφοράς πασσάλου, υπό αξονική φόρτιση μεγάλου εύρους, η οποία μπορεί να οδηγήσει σε απώλεια φέρουσας ικανότητας. Συγκεκριμένα, εξετάζεται ο συντελεστής στατικής δυσκαμψίας μεμονωμένου κατακόρυφου πασσάλου εμπεδωμένου σε ομοιογενές ή πολυστρωματικό έδαφος τυχαίας γεωμετρίας και μηχανικών ιδιοτήτων. Για την επίλυση του προβλήματος αναπτύσσεται αναλυτική λύση κλειστού τύπου βασισμένη στη θεωρία Winkler. Στο εν λόγω μοντέλο η προσομοίωση της μηχανικής συμπεριφοράς του εδάφους γίνεται μέσω μή-γραμμικών ελατηρίων “t-z” τοποθετημένων κατά μήκος του άξονα και στη βάση του πασσάλου, σε συνδυασμό με συναρτήσεις σχήματος, οι οποίες περιγράφουν αξιόπιστα την μεταβολή της κατακόρυφης μετακίνηση του πασσάλου με το βάθος. Με επιλογή κατάλληλης συνάρτησης σχήματος και καμπυλών “t-z”, και μετά από επαναληπτική διαδικασία εφαρμογής, επιτυγχάνεται ικανοποιητική ακρίβεια στην τιμή της δυσκαμψίας για κατακόρυφη μετακίνηση στην κεφαλή του πασσάλου. Σε αντίθεση με τις κλασικές αριθμητικές λύσεις, η προτεινόμενη μέθοδος δεν απαιτεί διακριτοποίηση του πασσάλου σε πεπερασμένα στοιχεία (και στη συνέχεια επίλυση ενός συστήματος γραμμικών εξισώσεων μεγάλης τάξης), παρά μόνο σε "κελιά" με στόχο την ολοκλήρωση με το βάθος. Έτσι, τα παραγόμενα αποτελέσματα είναι διαχείρισιμα ακόμα και μέσω απλού φύλλου εργασίας σε Excel ή και υπολογιστή τσέπης. Η μέθοδος προγραμματίστηκε σε περιβάλλον Visual Basic 2010, κυρίως λόγω της δυνατότητας γραφικής παρουσίασης των αποτελεσμάτων και τη σύγκρισή τους με αντίστοιχα αποτελέσματα από άλλες μεθόδους. Τα αποτελέσματα κρίνονται ως ιδιαίτερα ενθαρρυντικά, καθώς συγκλίνουν ικανοποιητικά σε αυτά αυστηρότερων μεθόδων, χωρίς ανάγκη περίπλοκης αριθμητικής ανάλυσης η οποία να ξεφεύγει από τις γνώσεις και δυνατότητες του Γεωτεχνικού Μηχανικού. / In the present work the behavior of a pile submitted to large range lateral loading is analyzed, which may lead to failure of both the surrounding soil and the pile itself either at the head or in depth. Namely, we examine the static stiffness coefficients for displacement and rotation of a flexible pile, vertically embedded in a homogeneous or multilayer soil of random geometry and mechanical properties. To solve the problem, a simple analytical method is developed, based on Euler–Bernoulli classic beam model, incremented with non linear Winkler Springs. The non-linear behaviour of the pile is described in a cross-sectional plane through moment-curvature diagram. The model is used in combination with the principle of work and suitable shape functions, which describe reliably the elastic line of the pile when the lateral load is gradually increasing. By iterative implementation of the method, realistic predictions are achieved in the stiffness coefficients in swaying, rocking and cross-swaying-rocking. The number of iterations is relatively small if the stress level of the system is not significantly increased compared with the previous load step. Unlike classic numerical solutions, the proposed method does not require discretization of the pile into finite elements (resulting to solve a system of linear equations), but only in "cells", to integrate with depth. In this way, results can be generated throughout a simple worksheet or even a calculator. The method was implemented in a Visual Basic 2010 environment, mainly for reasons of graphical presentation and comparison of the results to other coming from relevant methods. The results of the aforementioned method are considered satisfactory, as they converge fairly well with those coming from more rigorous methods based on complicated numerical analyses. The results of the herein proposed method are also compared to experimental in situ results relatively successfully.

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Earthquakes cause damages to structures and result in great human casualties and economic loss. A fraction of the kinetic energy released from earthquakes is transferred into buildings through soils. The investigation on the mechanism of the energy transferring from soils to buildings during earthquakes is critical for the design of earthquake resistant structures and for upgrading existing structures. In order to understand this phenomena well, a wave-soil-structure interaction analysis is presented. The earthquake wave-soil-structure interaction analysis of tall buildings is the main focus of this research. There are two methods available for modeling the soil-structure interaction (SSI): the direct method and substructure method. The direct method is used for modeling the soil and a tall building together. However, the substructure method is adopted to treat the unbounded soil and the tall building separately. The unbounded soil is modeled by using the Scaled Boundary Finite-Element Method (SBFEM), an infinitesimal finite-element cell method, which naturally satisfies the radiation condition for the wave propagation problem. The tall building is modeled using the standard Finite Element Method (FEM). The SBFEM results in fewer degrees of freedom of the soil than the direct method by only modeling the interface between the soil and building. The SBFEM is implemented into a 3-Dimensional Dynamic Soil-Structure Interaction Analysis program (DSSIA-3D) in this study and is used for investigating the response of tall buildings in both the time domain and frequency domain. Three different parametric studies are carried out for buildings subjected to external harmonic loadings and earthquake loadings. The peak displacement along the height of the building is obtained in the time domain analysis. The coupling between the building’s height, hysteretic damping ratio, soil dynamics and soil-structure interaction effect is investigated. Further, the coupling between the structure configuration and the asymmetrical loadings are studied. The findings suggest that the symmetrical building has a higher earthquake resistance capacity than the asymmetrical buildings. The results are compared with building codes, field measurements and other numerical methods. These numerical techniques can be applied to study other structures, such as TV towers, nuclear power plants and dams.

In this thesis primarily structural induced liquefaction potential was aimed to be analyzed. Also the effect of base isolation systems both on structural performance and liquefaction potential was studied. FLAC software was chosen for the analyses so that structure and soil could be modeled together. By these means the soil structure interaction effects were also examined. Four different structures and three different sites were analyzed under two different input motions. All the structures were also analyzed as base isolated. It was mainly found that depending on the structural type and for a certain depth the liquefaction potential could be higher under the structure than the one in the free field. Also it was concluded that base isolation systems were very effective for decreasing the story drifts, shear forces in the structure and liquefaction potential in the soil. It was also found that the interaction took place between structure, soil and input motions.

When a jack-up foundation is installed on seabeds consisting of a sand layer overlying soft clay, potential for 'punch-through' failure exists. This happens due to an abrupt reduction in bearing resistance when the foundation punches a block of sand into the underlying soft clay in an uncontrolled manner. This can lead to a sudden large penetration that can cause temporary decommissioning and even toppling of the unit. This research has addressed this problem with the aim of developing a practical design method for the jack-up industry to assess potential punch-through hazards. This objective has been achieved with the successful development of a new conceptual model for predicting the peak penetration resistance and a consistent method for constructing a complete resistance profile of spudcan foundations penetrating through sand into the underlying clay. The analytical basis of the new conceptual model follows the approach for silo analysis, and takes into account the stress level and dilatant response of sand. It is therefore a significant improvement over the punching shear and load spread models recommended in the current industry guidelines SNAME (2002), which do not consider the strength properties of the sand. To provide relevant experimental data for the new model, an extensive series of 30 continuous penetration tests were performed using the UWA drum centrifuge. These experimental results were retrospectively simulated using finite element (FE) analysis, in order to back-calculate the stress-level dependent friction and dilation angles in the sand during peak penetration resistance. The back-analysis showed that larger values of peak resistance gave lower friction and dilation angles, which is consistent with gradual suppression of dilatancy under high confining stress. When compared to published results from visualisation experiments, the FE analysis showed a similar failure mechanism during peak resistance, where a frustum of sand was forced into the underlying clay, with the outer angle reflecting the dilation in the sand. This has formed the basis of the new conceptual model. The performance of the new model in predicting the experimental peak resistance was compared with other existing analytical methods. Additional experimental results, including those already in the literature, were incorporated in the comparative study. It was found that the new conceptual model generally gave a good prediction of the experimental values, while the prediction from SNAME (2002) was conservative, with the predicted values being about half the experimental results on average. It was also shown that the new model could be modified to predict the post-peak penetration resistance in the sand layer. Finally, an analytical method for predicting the resistance profiles in the underlying clay was devised based on new bearing capacity factors developed through FE analysis. By joining the values of peak resistance, post-peak resistance and the resistance profile in the underlying clay, a complete simplified penetration resistance profile for spudcan foundations in sand overlying clay can be generated. The predicted profiles were shown to match the experimental results well.

A thermo-elastic-plastic model for unsaturated soils has been presented based on the effective stress principle considering the thermo-mechanical and suction coupling effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the solid skeleton and changes in fluid content and entropy for unsaturated soils have been established. A plasticity model is derived from energy considerations. The model derived covers both associative and non-associative flow behaviours and the modified Cam-Clay is considered as a special case. All model coefficients are identified in terms of measurable parameters. To verify the proposed model, an experimental program has been developed. A series of controlled laboratory tests were carried out on a compacted silt sample using a triaxial equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing technique was used for measuring the volume change of the samples subjected to mechanical, thermal and hydric loading. It is shown that the effective critical state parameters M, ???? and ???? are independent of temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve was affected by temperature and suction. Furthermore, the temperature change affected the soil water characteristic curve and an increase in temperature caused a decrease in the air entry suction. The simulations from the proposed model are compared with the experimental results. The model calibration was performed to extract the model parameters from the experimental results. Good agreement between the results predicted using the proposed model and the experimental results was obtained in all cases.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work deals with the consideration of Soil-Structure Interaction (SSI) in structural design of reinforced concrete buildings on shallow foundations of the isolated footing type. It carried out a comprehensive review on the major works done in the area and the methods for obtaining parameters and variables involved in the analysis. Numerical examples were developed with the aim of identifying internal forces and displacements changes caused by considering the deformation of soil and the construction sequence in the structural analysis. The examples also intended to show data and procedures for the required calculations in the consideration of the SSI in structural designs. Among the computational tools used in the numerical examples is ESPACIAL_ISE program - a program developed in FORTRAN by Alva (2010). This program employs the method of Aoki and Lopes (1975), which uses the equations of Mindlin (1936) for calculating the settlements, together with the Steinbrenner´s method (1934) to consider the stratigraphy of the soil mass. It was also used in the numerical examples SISEs computer system (System of Soil-Structure Interaction) - developed by TQS Informatics - which allows that the entire structure and foundation are represented in a single structural model. The results of this study showed the importance of considering the soil deformation, although in a simplified form, replacing the fixed support hypothesis in structural designs. Thus, for a more realistic structural analysis of multistory buildings, it is recommended that the soil-structure interaction is considered together with the construction sequence. / O presente trabalho trata da consideração da Interação Solo-Estrutura (ISE) em projetos estruturais de edifícios em concreto armado sobre fundações superficiais do tipo sapatas isoladas. É realizada uma ampla revisão bibliográfica sobre os principais trabalhos desenvolvidos na área e sobre os métodos para a obtenção de parâmetros e variáveis envolvidos na análise. Exemplos numéricos foram desenvolvidos com o intuito de identificar as alterações de esforços e deslocamentos ocasionadas ao se considerar a deformabilidade do solo e a sequência construtiva na análise estrutural. Os exemplos também tiveram como objetivo mostrar os dados e os procedimentos de cálculo necessários para a consideração da ISE em projetos estruturais. Entre as ferramentas computacionais utilizadas nos exemplos numéricos está o programa ESPACIAL_ISE - programa desenvolvido em linguagem FORTRAN por Alva (2010). O referido programa emprega o método de Aoki e Lopes (1975), o qual utiliza as equações de Mindlin (1936) para o cálculo dos recalques, em conjunto com o procedimento de Steinbrenner (1934) para considerar a estratigrafia do maciço de solos. Também foi utilizado nos exemplos numéricos o sistema computacional SISEs (Sistema de Interação Solo-Estrutura) desenvolvido pela TQS Informática - o qual permite que toda a estrutura e a fundação sejam representadas em um modelo estrutural único. Os resultados obtidos neste trabalho mostraram a importância da consideração da deformabilidade do solo, ainda que de forma simplificada, em substituição à hipótese de apoios indeslocáveis nos projetos estruturais. Para uma análise estrutural mais realista em edifícios de múltiplos andares, recomenda-se que a interação solo-estrutura seja considerada juntamente com a sequência construtiva.

Apresenta-se uma ferramenta para análise de edifícios de concreto armado assentados sobre sapatas, capaz de avaliar os efeitos decorrentes da deformabilidade do maciço de solos nas peças da superestrutura (lajes, vigas e pilares) e nos elementos estruturais de fundação (EEF). O software possibilita uma análise mais refinada das solicitações e, conseqüentemente, do real comportamento mecânico da estrutura. O programa ISE (Interação Solo-Estrutura), desenvolvido em linguagem FORTRAN, realiza o cálculo dos deslocamentos segundo o método proposto por Aoki & Lopes em 1975, que por sua vez faz uso das equações apresentadas por Mindlin em 1936, com base na teoria da elasticidade. Devido à grande variabilidade, o solo é tratado como meio heterogêneo, recorrendo-se ao procedimento sugerido por Steinbrenner, em 1934, para cálculo de recalques em meios estratificados. O método dos elementos finitos (MEF) é empregado na modelgagem dos EEF como elementos de casca planos, para determinação das componentes de deslocamento u, v e w. A compatibilização de deslocamentos, na região de contato entre a superfície de assentamento e a face inferior das sapatas, é condição necessária e suficiente para garantir o equilíbrio e a continuidade. Com o intuito de tornar mais amigável o uso do código computacional, é criada uma interface gráfica em Delphi e gerado um arquivo com extensão DXF, possibilitando a visualização da geometria do sistema de fundação. A elaboração de exemplos comprova a validade da formulação desenvolvida, por meio da comparação com resultados de outras metodologias presentes na literatura / This work presents a tool for reinforced concrete building based in direct foundation analysis able to evaluate effects in the superstructure constituent (slab, beams and columns) and foundation structural elements (FSE) resulting from soil deformability, making possible an efforts sophisticated analysis and real mechanical behavior of the structure. The program SSI (Soil-Structure Interaction), developed in FORTRAN language, calculates displacements increases by the Aoki & Lopes’s method. Proposed in 1975, the method uses de Mindlin’s equations showed in 1936 and based in the theory of elasticity. Due great variability, the soil is treated like a heterogeneous medium, appealing to the Steinbrenner proceeding suggested in 1934, for the estimate of displacements in multilayers medium. The finite element method (FEM) is used in FSE modeling as shell elements for determination of displacements components u, v and w. The displacements compatibilization in contact zone between surface support and FSE below side is necessary and sufficient condition for equilibrium guarantee and continuity. Turning more friendly the software use, a graphical interface, in Delphi, is made and created a DXF file, making possible the geometry visualization of foundation system. The examples elaboration prove the developed formulation validity through results comparison with others methodologies

Neste trabalho apresenta-se um modelo numérico para a análise de problemas tridimensionais envolvendo a interação mecânica estaca-solo, acoplando-se o Método dos Elementos de Contorno (MEC) ao Método dos Elementos Finitos (MEF). O solo é modelado com o MEC utilizando-se as soluções fundamentais de Mindlin, assumindo um meio semi-infinito, homogêneo, isotrópico e elástico-linear. As estacas, modeladas com o MEF, consistem em um elemento único, com quatro nós e 14 parâmetros nodais (três deslocamentos em cada nó e mais duas rotações no topo da estaca). Cada uma das estacas é levada em consideração no MEC como uma linha de carga. Considera-se o escorregamento das estacas em relação ao maciço, empregando modelos de aderência para a definição da evolução das tensões tangenciais ao longo do comprimento das estacas. São empregados, como funções de forma, polinômios do quarto grau para os deslocamentos horizontais, cúbicos para os deslocamentos verticais e tensões horizontais ao longo do fuste e quadráticos para as tensões verticais do fuste e escorregamento. A reação da ponta da estaca é calculada assumindo tensão constante na base. / This work presents a method for tri-dimensional pile-soil interaction problems, by coupling the Boundary Element Method (BEM) to the Finite Element Method (FEM). The soil is modeled with BEM, using the Mindlins fundamental solutions, supposing a semi-infinite, homogeneous, isotropic, elastic and linear space. Piles are modeled with FEM and are represented by one element with four nodes and 14 nodal parameters (three displacements in each node and two rotations at the top node). Each pile is represented in BEM as a line load. The pile slip is considered using adherence models to evaluate the evolution of shaft tractions. There are employed fourth grade polynomial shape functions for horizontal displacements, cubic polynomial functions for vertical displacements and horizontal tractions along shaft and quadratic polynomial functions for vertical tractions and slip. Tip reaction is calculated supposing constant traction at the base.

Nesta pesquisa estudou-se a influência de recalques em edifícios de alvenaria estrutural. Inicialmente os efeitos desses deslocamentos foram avaliados por meio de uma investigação numérica preliminar. A partir das análises realizadas foram definidos alguns casos mais interessantes de painéis constituídos por parede de alvenaria sobre viga de concreto armado para serem submetidos a ensaios em laboratório. Desta forma foi possível observar experimentalmente o comportamento desses painéis, variando-se alguns dos parâmetros mais importantes: existência e tipo de abertura e rigidez da viga. Além disso, foram avaliadas algumas alternativas para a minimização da fissuração. Utilizando os resultados experimentais, foram realizadas novas análises numéricas com o intuito de validar a modelagem adotada. Verificou-se em especial a importância de consideração da não-linearidade de contato. / In this research, the influence of settlements on structural masonry buildings has been studied. Initially the effect of these displacements was evaluated by means of a preliminary numerical investigation. From these analyses, some interesting cases of panels made of masonry wall on reinforced concrete beam were defined to be submitted to laboratory tests. Thus, it was possible to experimentally observe the behavior of these panels, varying some of the most important parameters: existence and type of opening and rigidity of the beam. Moreover, some cracking minimization alternatives have been evaluated. Using the experimental results, new numerical analyses have been performed to validate the modeling adopted. The importance of contact non-linearity consideration has been specially verified.