Comprendre comment s’initie une subduction au niveau d’une marge passive est un problème géodynamique majeur, mais il reste très débattu en raison des forces nécessaires pour provoquer la flexion de la plaque plongeante, et dépasser la résistance frictionnelle de la lithosphère pour localiser cette subduction. Formant la bordure sud de la Méditerranée Occidentale, la marge algérienne subit des conditions aux limites en compression en raison de la convergence Afrique-Eurasie à un taux de moins de 1 cm/an. Ce contexte favorise l’inversion de cette marge nord-africaine et possiblement le début d’une subduction. En effet, des données géophysiques récentes acquises dans le bassin algérien (campagnes de MARADJA, 2003, 2005 (MARge Active d’el Djazaïr) et SPIRAL 2009 (Sismique Profonde et Investigations Régionales en ALgérie) ont montré des indices de déformation compressive récente. Nous avons utilisé les profils SPIRAL afin de calculer l’état isostatique de la lithosphère au voisinage de la limite océan-continent. Ceci nous a permis d'imager un Moho trop profond dans le domaine océanique, et plus superficiel dans le domaine continental, de part et d'autre d'une limite située vers le pied de pente de cette marge, donc un déséquilibre isostatique général de la marge. Nos résultats indiquent que la marge algérienne montre les mêmes anomalies isostatiques qu’au niveau d'une marge active, avec une zone de découplage océan/continent située en pied de marge. Ces anomalies peuvent être interprétées par un mécanisme de flexure des deux lithosphères en présence, que l’on peut simuler ensuite par une modélisation en éléments finis d’une plaque mince élastique. / Understanding how subduction initiates at a passive margin is a major geodynamic question, which remains debatted because of the forces necessary to overcome bending and frictional resistance of the lithosphere and initiate this subduction. Along the southern shore of the Western Mediterranean Sea, the Algerian margin undergoes ~NS compression due to the African-Eurasian convergence at a rate of less than ~ 1 cm / year. This setting causes tectonic inversion of this North African passive margin and possibly incipient subduction. Indeed, recent geophysical marine data acquired in the Algerian Basin (MARADJA, 2003, 2005MARge Active d’el Djazaïr) and SPIRAL 2009 (Deep Seismic and Regional Investigations in Algeria campaigns) showed evidence of recent compressive deformation. We used SPIRAL wide-angle seismic profiles to determine the state of isostatic equilibrium at the vicinity of the continent-ocean boundary. This allowed us to image a too deep Moho in the oceanic part, and a too shallow one in the continental domain, with a boundary between both domains located at the margin toe. These results indicate that the Algerian margin display the same isostatic anomalies as an active margin. This isostatic disiquilibrium may be simulated by the flexural bending of two lithospheric plates that can be modelled by a finite element procedure. This modeling shows larger vertical deflection in the central part of the study area (6-7 km) compared to the earsternmost and westernmost profiles (3 km).

Les bassins d'avant-pays se développent au front des orogènes par flexure de la lithosphère. L'héritage structural et thermique de celle-ci joue un rôle fondamental dans leur évolution et différentes sources peuvent contribuer à la subsidence du bassin. Cette thèse analyse les effets de l'héritage d'un épisode de rift sur un rétro-bassin d'avant-pays qui s'est développé alors que la lithosphère n'avait pas retrouvé son état d'équilibre. Le Bassin Aquitain est le rétro-bassin d'avant-pays pyrénéen qui s'est développé au Campanien-Miocène. L'orogenèse pyrénéenne fait suite à un épisode de rifting Aptien-Cénomanien durant lequel la croûte a été fortement amincie et le manteau sous-continental exhumé. Les effets de l'héritage crustal dus au rift sur l'évolution du bassin sont étudiés par une analyse des structures dans la croûte, du comportement flexural de la plaque européenne et de la distribution des sédiments synorogéniques. L'évolution de la subsidence dans le bassin est étudiée par analyse de subsidence 1D d'après des données de forages. Enfin, les mécanismes d'inversion de la marge européenne sont étudiés par restauration d'une coupe structurale à échelle crustale. Cette étude aide à définir le rôle de l'héritage d'un ancien système de rift sur la mise en place et l'évolution d'un bassin d'avant-pays ainsi que le rôle des différentes sources de subsidence et leurs variations spatio-temporelles. Cette étude démontre également les liens étroits entre l'histoire du rétro-bassin d'avant-pays et les mécanismes et phases d'inversion de la marge hyper-amincie / Foreland basins develop in front of orogens by flexure of the lithosphere. When they initiate over a crust that has been affected by a previous tectonic event, structural and thermal inheritance have a fundamental role in their evolution and different sources may contribute to basin subsidence. The present work analyzes the impact of inheritance from a rifting event on a foreland basin, which develops while thermal reequilibration has not been achieved at the time of loading. The Aquitaine Basin is the Pyrenean retro-foreland basin that developed from Campanian to Miocene. The Pyrenean orogenesis follows an Aptian-Cenomanian rifting during which the continental crust is thinned and sub-continental mantle exhumed. The orogenesis starts only 10 Myr after the end of rifting. The effects of crustal inheritance due to rifting on the evolution of the basin are studied by analyzing crustal structures, flexural behavior of the European plate, and foreland succession distribution. The subsidence evolution of the basin is studied by the 1D backstripping technique using borehole data. Finally, inversion mechanisms of the European margin are studied by cross-section construction and restoration at crustal scale. This study helps to define the role of rift inheritance on the initiation and the evolution of a retro-foreland basin, as well as the relative role of subsidence sources and their variations in space and time. The present work also shows the strong relationship between the retro-foreland basin's history and both mechanism and the history and mechanisms of inversion of a hyper-extended margin

No description available.

published_or_final_version / abstract / Civil Engineering / Master / Master of Philosophy

Fibre reinforced polymers (FRPs) have gained considerable popularity as a building and repair material. In particular, FRPs have been an economical means of extending the life of structures. As time passes, an increased number and variety of new and old structures are incorporating FRPs as reinforcement and for rehabilitation. Perhaps most common are their applications for bridge structures. Much of the reluctance towards the inclusion of FRP as primary reinforcement or as a rehabilitation measure in building structures is due to its poor performance in fires. In order to move forward with an understanding of how FRP may overcome its temperature-related short comings, it is important to explore the behaviour of FRP, and structures which utilize FRP for reinforcement, at elevated temperatures. The results of a testing program including eleven high temperature, two room temperature intermediate-scale, FRP-strengthened, and one unstrengthened reinforced concrete beam tests are presented. The elevated temperature tests were conducted on both un-post-cured and post-cured FRP strengthening at temperatures up to 211°C. The tests also utilized a novel method for heating and post-curing FRP-strengthening in place. The strengthened beams exhibited strength gains above the unstrengthened reference beam, and it has been demonstrated that post-curing of an FRP system can be effective at increasing an FRP’s performance at elevated temperatures. Exposed to constant temperatures, un-post-cured specimens still exhibited substantial FRP strength at exposure temperatures up to Tg+79°C. Post-cured specimens exhibited similar performance at temperatures of Tg+43°C. The transient temperature tests resulted in ii beam failure at an average temperature of 186°C and 210°C for un-post-cured and post-cured FRP strengthening respectively at a constant applied load level 93% of that of the room temperature strengthened control beam. The results of this testing program demonstrate that FRP strengthening can remain effective when exposed to temperatures well above the measured value of Tg. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-02-28 15:14:31.336

The Wilkes Land margin of East Antarctica, conjugate to the southern Australian margin, is a non-volcanic rifted margin that formed during the Late Cretaceous. During 2000-01 and 2001-02, Geoscience Australia (GA) acquired ~10,000 line km of seismic reflection, magnetic anomaly, and gravity anomaly data, on the Wilkes Land margin. Seismic reflection and sonobuoy refraction data provide the first constraints on sediment thickness and images of the deep crustal structure for the extent of the Wilkes Land margin. Two major post-rift seismic-stratigraphic sequences are recognised, separated by a regionally correlatable unconformity. The unconformity is interpreted as Early- to Middle-Eocene (~50 Ma). This unconformity has previously been interpreted to represent the onset of continent-wide glaciation at ~34 Ma. A major unconformity at the base of post-rift sediments is interpreted as a breakup unconformity, of approximately Turonian (85-90 Ma) age. Timing the onset of seafloor spreading using lineated magnetic anomalies within the Australia-Antarctic Basin (AAB) is extremely difficult due to uncertainties in correlating anomalies to the geomagnetic reversal time scale. Modelling indicates that the anomaly commonly correlated to Chron 34y may, in some cases, be associated with high level intrusions and/or serpentinisation of exhumed upper-mantle peridotites. Process-oriented gravity modelling indicates that the Wilkes Land margin lithosphere is characterised by a relatively high effective elastic thickness (Te). Isostatic anomalies are most effectively reduced for models utilising Te = 30 km. Although the margin is broadly characterised by a high Te, zones of low Te are inferred from modelling. Spectral analysis of isostatic anomalies indicates that the power of the flexural isostatic anomalies is lower than the free air gravity anomalies. The margin does not appear to be segmented, at least in regard to its long-term strength. However, a change in initial, zero-elevation crustal thickness (Tc) is inferred from west to east. A Tc of ~35 km is inferred for western Wilkes Land, whereas eastern Wilkes Land is characterised by Tc = 29 to 31 km. Limited seismic refraction data from the conjugate margin indicates a similar trend from southwest to southeast Australia.

The high cost of repairing reinforced or prestressed concrete structures due to steel corrosion has driven engineers to look for solutions. Much research has been conducted over the last two decades to evaluate the use of Fiber Reinforced Polymers (FRPs) in concrete structures. Structural engineering researchers have been testing FRP to determine their usability instead of steel for strengthening existing reinforced concrete structures, reinforcing new concrete members, and for prestressed concrete applications. The high strength-to-weight ratio of FRP materials, especially Carbon FRP (CFRP), and their non-corrosive nature are probably the most attractive features of FRPs. In this study, an experimental program was conducted to investigate the flexural behavior of prestressed concrete beams pre-tensioned with CFRP strands. The bond characteristics were examined by means of experimentally measuring transfer length, flexural bond length, and bond stress profiles. A total of four rectangular beams pre-tensioned with one 0.5-in. diameter CFRP strand were fabricated and tested under cyclic loading for five cycles, followed by a monotonically increasing load until failure. In investigating bond properties, the experimental results were compared to the equations available in the literature. The results from the four flexural tests showed that the main problem of CFRP strands, in addition to their liner-elastic tensile behavior, was lack of adequate bonding between FRP and concrete. Poor bonding resulted in early failure due to slippage between FRPs and concrete. As a result, a new technique was developed in order to solve the bonding issues and improve the flexural response of CFRP prestressed concrete beams. The new technique involved anchoring the CFRP strands at the ends of the concrete beams using a new "steel tube" anchorage system. It was concluded that the new technique solved the bond problem and improved the flexural capacity by about 46%. A computer model was created to predict the behavior of prestressed beams pre-tensioned with CFRP. The predicted behavior was compared to the experimental results. Finally, the experimental results were compared to the behavior of prestressed concrete beams pre-tensioned with steel strands as generated by the computer model. The CFRP beams showed higher strength but lower ductility.

This thesis has investigated the application of CFRP and GFRP bars as longitudinal reinforcement for continuously supported concrete beams. Two series of simply and continuously supported CFRP and GFRP reinforced concrete beams were tested in flexure. In addition, a continuously supported steel reinforced concrete beam was tested for comparison purposes. The FRP reinforced concrete continuous beams were reinforced in a way to accomplish three possible reinforcement combinations at the top and bottom layers of such continuous beams. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported FRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. However, continuous concrete beams reinforced with CFRP bars exhibited a remarkable wide crack over the middle support that significantly influenced their behaviour. The ACI 440.1R-06 equations have been validated against experimental results of beams tested. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably predict the load capacity and deflection of the simply and continuously supported GFRP reinforced concrete beams tested. However, The potential capabilities of these equations for predicting the load capacity and deflection of continuous CFRP reinforced concrete beams have, however, been adversely affected by the de-bonding of top CFRP bars from concrete. An analytical technique, which presents an iterative procedure based on satisfying force equilibrium and deformation compatibility conditions, has been introduced in this research. This technique developed a computer program to investigate flexural behaviour in particular the flexural strength and deflection of simple and continuously supported FRP reinforced concrete beams. The analytical modelling program has been compared against different prediction methods, namely ACI 440, the bilinear method, mean moment inertia method and Benmokrane's method. This comparison revealed the reliability of this programme in producing more enhanced results in predicting the behaviour of the FRP reinforced beams more than the above stated methods.

[pt] Esta tese apresenta o fenômeno de ruptura por tombamento bloco-flexural, que acontece na zona NW da mina Tintaya. O objetivo do presente estudo é contribuir o conhecimento de este tipo de fenômeno de ruptura, quantificando as características do maciço rochoso com as técnicas da mecânica das rochas. O trabalho inicia-se por uma caracterização geral da zona de estudo, com especial relevo das propriedades geomecánicas das descontinuidades presentes, pelo que foram desenvolvidos mapeamentos das caras de bancada e a amostragem da rocha intacta, esta data permitiu estabelecer correlações dos parâmetros geomecânicos e fazer a análise cinemática da zona de estudo. Após de fazer a caracterização e avaliação das características das descontinuidades, foi definido o tombamento bloco-flexural, pelo jeito das descontinuidades presentes no maciço, já que este tipo de ruptura é mais complexo do que os outros tipos de tombamento, porque é uma combinação de tombamento e deslizamento dos blocos. Em vez da ruptura flexural de colunas contínuas, neste caso o tombamento é resultado de deslocamentos acumulados das juntas transversais. Com o objetivo de fazer uma análise numérica, obtou-se por um modelo contínuo- equivalente que inclui os efeitos de orientação e espaçamento das juntas é o modelo de plasticidade de Cosserat. O contínuo de Cosserat, conhecido também como contínuo micropolar acrescenta os graus de liberdade de rotação ao contínuo convencional. Pelo que foi analisado este tipo de ruptura através de uma modelagem computacional com um programa de elementos finitos feito na PUC-Rio, assim, tornar possível a modelagem computacional com a teoria do continuo de Cosserat. / [en] This thesis presents the block - flexural toppling failure phenomenon, which happens at NW zone of the Tintaya´s mine. The objective of the present study is to contribute the knowledge of this type of phenomenon of failure, quantifying the characteristics of rock mass with the techniques of the rock mechanics. The work begins for a general characterization of the zone, with special relief of the geomechanical properties of the discontinuities, which were developed the window sampling (bench face mapping) and sampling of the intact rock, this information allowed to establish correlations of the geomechanical parameters and make feasible kinematics analysis from the zone of study. After doing the rock mass characterization and evaluation of the characteristics of the discontinuities, the block - flexural toppling failure was defined, on those long column rocks crossed by numerous huge subhorizontal joints. The block-flexural type failure is a complex phenomenon compared with other types of toppling failure, because it is a combination of pure toppling and sliding. With the intention of numerical analysis, I have been proposed analyzing this rupture for a continuum - equivalent model of Cosserat, that includes the orientation and the discontinuity´s spacing. This model is known also as continuum micropolar, which adds the degrees of freedom of rotation to a conventional continuum. It was analyzed this type of failure through a computational modeling with a program of finite elements made in the PUC-Rio, so, the computational modeling possible with the theory of continuum of Cosserat.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / Microfiche copy available in Archives and Barker. / Includes bibliographical references. / by Steven James Hollowell. / M.S.