Foundation uplift is the partial separation of a shallow foundation from soil due to excessive load eccentricity. Foundation uplift can significantly change the seismic response of slender structures, and frames as well. In literature, different support models for foundations are employed in order to simulate foundation uplift in seismic analysis of structures. One of the most widely used models is the Winkler model which assumes distributed tensionless springs beneath a shallow foundation. In this study, two simple algorithms are developed in order to compute static and dynamic response of foundations on tensionless supports. Any formula given in literature for calculation of foundation impedance coefficients can be easily introduced in these algorithms. Hence, the use of Winkler model is critically evaluated through comparisons with the response of a foundation on elastic halfspace. For that purpose, available impedance formulas given for a shallow rectangular foundation on elastic halfspace are used. It is concluded that, the coupling between vertical displacement and rocking of foundation is very significant during uplift. Therefore, the accuracy of Winkler model in uplift v simulation is limited, since the model cannot simulate vertical and rocking response of a shallow foundation concurrently with a single spring coefficient.

The recent 2011 Tōhoku earthquake and tsunami served as a stark reminder of the destructive capabilities of such combined events. Civil Engineers are increasingly tasked with protecting coastal populations and infrastructure against more severe multi-hazard events. Whilst the protective measures must be robust, their deployment over long stretches of coastline necessitates an economical and environmentally friendly design. The dual row retaining wall concept, which features two parallel sheet pile walls with a sand infill between them and tie rods connecting the wall heads, is potentially an efficient and resilient system in the face of both earthquake and tsunami loading. Optimal use of the soil's strength and stiffness as part of the structural system is an elegant geotechnical solution which could also be applied to harbours or elevated roads. However, both the static equilibrium and dynamic response of these types of constructions are not well understood and raise many academic and practical challenges. A combination of centrifuge and numerical modelling was utilised to investigate the problem. Studying the mechanics of the walls in dry sand from the soil stresses to the system displacements revealed the complex nature of the soil structure interaction. Increased wall flexibility can allow more utilisation of the soil's plastic capacity without necessarily increasing the total displacements. Recognising the dynamically varying vertical effective stresses promotes a purer understanding of the earth pressures mobilised around the walls and may encourage a move away from historically used dynamic earth pressure coefficients. In a similar vein, the proposed modified Winkler method can form the basis of an efficient preliminary design tool for practice with a reduced disconnect between the wall movements and mobilised soil stresses. When founded in liquefiable soil and subjected to harmonic base motion, the dual row walls were resilient to catastrophic collapse and only accrued deformation in a ratcheting fashion. The experiments and numerical simulations highlighted the importance of relative suction between the walls, shear-induced dilation and regained strength outside the walls and partial drainage in the co-seismic period. The use of surrogate modelling to automatically optimise parameter selection for the advanced constitutive model was successfully explored. Ultimately, focussing on the mechanics of the dual row walls has helped further the academic and practical understanding of these complex but life-saving systems.

Caisson or pier foundations are encountered as part of the foundation system of tall structures such as bridges, transmission towers, heliostats, etc, and correspond to rigid blocks of length-to-diameter (D/B) ratio on the order of D/B = 2-6. As a result of their geometry and stiffness characteristics, the mechanisms of load transfer from the superstructure to the surrounding soil and their kinematic response to seismic wave propagation are governed by a complex stress distribution at the pier-soil interface, which cannot be adequately represented by means of simplified Winkler models for shallow foundations or flexible piles. Continuum model solutions, such as 3D finite elements (FE) cannot be employed frequently in practice for the design of non-critical facilities due to the cost and effort associated with these analyses. The objective of this work is to develop a Winkler-type model for the analysis of transversely-loaded caissons, which approximately accounts for all the main soil resistance mechanisms mobilized, while retaining the advantages of simplified methodologies for design at intermediate levels of target accuracy. Investigation of the governing load-transfer mechanisms and development of complex spring functions is formulated on the basis of 3D FE simulations. Initially, the soil-structure stiffness matrix is computed by subjecting the pier to transverse static and dynamic loading at the top, and numerically estimating the response. Complex frequency-dependent functions are next developed for the spring constants by equating the stiffness matrix terms to the analytical expressions developed for the four-spring model. Sensitivity analyses are conducted for optimization of the truncated numerical domain size, finite element size and far-field dynamic boundary conditions to avoid spurious wave reflections. Simulations are next conducted to evaluate the transient response of the foundation subjected to vertically propagating shear waves, and results are compared to the response predicted by means of the 4-spring model. Finally, the applicability of the method is assessed for soil profiles with depth-varying properties. While the methodology developed is applicable for linear elastic media with no material damping, the expressions of complex spring functions may be extended to include hysteretic damping, nonlinear soil behavior and soil-foundation interface separation, as shown in the conclusions.

Ce travail s'inscrit dans la continuité des travaux de recherche menés au laboratoire Géoressources (Ecole des Mines de Nancy) et à l'INERIS depuis plusieurs années. Il concerne l’évaluation de la vulnérabilité des ouvrages situés dans des zones de mouvement de terrains d’origine naturelle ou anthropique. L’objectif de la thèse est de développer un modèle analytique permettant l’évaluation du tassement différentiel d’un ouvrage soumis à un mouvement de terrain et de calculer le taux de transmission de ces mouvements en fonction de la rigidité relative de l’ouvrage. Le modèle d’interaction sol-structure développé, tient compte de l’influence des contraintes de cisaillement dans le bâti et le terrain et d’un comportement poste-rupture du sol grâce à l’introduction d’une limite de plasticité. Le sol a été modélisé par les éléments de Pasternak afin de prendre en compte l'influence des déformations de cisaillement dans le sol, alors que le bâtiment est modélisé par la poutre d'Euler-Bernoulli et par la poutre de Timoshenko. L’existence potentielle d’un vide (décollement) sous le bâtiment a également été prise en compte dans le modèle analytique développé. Le taux de transmission des mouvements en champ libre du terrain au bâtiment a été calculé et présenté en fonction de la rigidité relative en flexion du bâtiment par rapport au terrain. Pour valider le développement entrepris, les résultats du modèle analytique ont été comparés aux résultats de modèles existants, analytiques, numériques et expérimentaux développés principalement par l'Université de Cambridge. Les résultats obtenus sont très satisfaisants et permettant de confirmer la robustesse du modèle analytique développé / This work is a continuation of the research work conducted in the Géoressources Laboratory and INERIS since several years. It concerns the assessment of the vulnerability of masonry structures influenced by natural or induced ground movements. The origins of the movement are may be, mining subsidence, tunneling, and shrinkage-swelling of clayed ground. The objective of the thesis is to develop an analytical model to evaluate the differential settlement of a structure in relation to the free field ground movement and given a set of phenomena: soil-structure interaction, influence of shear deformations in the structure and the ground, influence of non- linearities induced by the ground yielding. The soil was modeled by Pasternak elements to take into account the influence of shear deformations in the soil, while the building is modeled by the Euler-Bernoulli beam and by the beam of Timoshenko. The possibility of having a gap under the building was also taken into account. The deflection transmission ratio is then calculated and plotted according to are lative stiffness ratio which depend on both the structure and the soil stiffness A numerical model is also developed and results are compared with those of the analytical model. Other results of several numerical and experimental models principally developed at the University of Cambridge are also used for this comparison. Results show significant consistence between all these results. This demonstrates the significance of the analytical soil-structure model developed in this thesis

Thesis (Ph.D, Civil Engineering) -- Queen's University, 2011-01-31 20:52:11.162 / One of the most severe hazards for buried pipelines, which are sometimes referred to as lifelines due to their essential role in delivering vital resources, is the hazard due to Permanent Ground Deformation (PGD). Earthquake induced PGD can be caused by surface faulting, landslides and seismic settlement. In this thesis, the behaviour of buried pipelines subject to normal faulting has been experimentally investigated through a series of centrifuge tests performed on both continuous and jointed pipelines. Both pipe and soil displacements were measured using image analysis. Signal processing techniques were then developed to filter this data so as to enable the calculation of curvature and other aspects of the response from the observed pipe deformations. First, a series of centrifuge tests was conducted on continuous pipelines of varying materials, representing a wide range of pipe stiffness relative to the soil and investigating the effect of pipe stiffness relative to the soil on soil-pipe interaction. The experimentally derived p-y curves at different locations along the pipe were compared to the recommended soil-pipe interaction models in the relevant guidelines. These p-y curves showed that the central shearing region was not captured well with independent soil springs. The response of the pipelines predicted by the ALA (2001) guideline, however, was shown to match the experimental data within 50%. Two new simplified design approaches were then developed. The first features calculations based on simplified pressure distributions. The second featured peak curvature normalized using a characteristic length, ipipe, the distance from peak to zero moment. A series of centrifuge tests using brittle pipes was also performed. The pipes were buried at three different depths, and the post-failure fracture angle of the pipe was measured to be used as an input for design of liners. Based on the experimental data, a computationally efficient approach was developed to estimate the initial fracture angle which occurs immediately after the pipe breaks. The last series of centrifuge tests was conducted on jointed pipelines with five different joint stiffnesses to investigate the flexural behaviour of jointed pipelines under normal faulting. Based on the observed pipe response, a simplified kinematic model was proposed to estimate the maximum joint rotation for a given geometry, pipe segment length, and the magnitude of the imposed ground displacement. / Ph.D

The diploma thesis deals with analytical description of vehicle - track dynamic interface. There are described basic analytical models which are subsequently extended in order to get a more precise description of dynamic phenomena. The aim is to compile a model that faithfully describes the dynamic phenomena in the track. These new compiled models are qualitatively compared with data obtained by measuring in the track.