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Ten reinforced-concrete continuous deep beams with openings were tested to failure. The main variables investigated were the shear span-to-overall depth ratio, and the size and location of openings. Two failure modes influenced by the size and location of web openings regardless of the shear span-to-overall depth ratio were observed. The normalised load capacity of beams having a web opening area ratio of 0.025 within exterior shear spans was approximately similar to that of their companion solid beams. Continuous deep beams having web openings within interior shear spans exhibited a higher load capacity reduction with the increase of the opening size, similar to simply supported deep beams with web openings. Formulae based on the upper bound analysis of the plasticity theory were proposed to predict the load capacity of continuous deep beams with web openings. Comparisons between the measured and predicted load capacities showed a good agreement.

Yes / Although the depth of reinforced concrete deep beams is much higher than that of slender beams, extensive existing tests on deep beams have focused on simply supported beams with a scaled depth below 600 mm. In the present paper, test results of 12 two-span reinforced concrete deep beams are reported. The main parameters investigated were the beam depth, which is varied from 400 mm to 720 mm, concrete compressive strength and shear span-tooverall depth ratio. All beams had the same longitudinal top and bottom reinforcement and no web reinforcement to assess the effect of changing the beam depth on the shear strength of such beams. All beams tested failed owing to a significant diagonal crack connecting the edges of the load and intermediate support plates. The influence of beam depth on shear strength was more pronounced on continuous deep beams than simple ones and on beams having higher concrete compressive strength. A numerical technique based on the upper bound analysis of the plasticity theory was developed to assess the load capacity of continuous deep beams. The influence of the beam depth was covered by the effectiveness factor of concrete in compression to cater for size effect. Comparisons between the total capacity from the proposed technique and that experimentally measured in the current investigation and elsewhere show good agreement, even though the section depth of beams is varied.

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A presente dissertação trata do estudo experimental do comportamento estrutural de barras helicoidais assentadas sobre superfície cilíndrica e sujeitas a cargas de compressão. Aparato experimental específico foi projetado e construído para este fim. O projeto, bem como a aferição deste aparato, é descrito em detalhes. Este aparato permite ajustar as barras através de um sistema de apoios constituídos por uma série de rolamentos, que podem ser posicionados de forma a conferir liberdade de deslocamento à barra em duas direções distintas: radial (normal à superfície cilíndrica de assentamento) e lateral (tangencial; bi-normal). A aplicação de carga compressiva se faz na direção tangencial à hélice não-deformada. Barras com seção transversal circular e retangular, com diversos comprimentos livres de flambagem e para diferentes ângulos de assentamento, foram ensaiadas. Estudos preliminares, com barras retas, permitiram avaliar as condições efetivas de engastamento proporcionadas pelo aparato. Nestes casos foi possível induzir o fenômeno de flambagem, recuperando-se, consistentemente, os valores de cargas críticas previstas pela teoria de Euler e avaliando-se o grau de engastamento proporcionado pelo aparato experimental. Filmagem com câmera de alta velocidade permitiu observar o fenômeno de instabilidade. O comportamento estrutural das barras curvas, de seção circular e retangular, foi então estudado. Tanto o comprimento livre quanto o ângulo de assentamento foi variado. O estudo permitiu levantar base de dados experimentais do comportamento de barras helicoidais nessas condições de carregamento e de condições de contorno. No entanto, para nenhuma das diversas condições ensaiadas foi possível induzir o fenômeno de instabilidade. Tal fato poderia dar subsídios a inferências acerca do estudo da instabilidade de tubos flexíveis do tipo birdcaging. / This dissertation deals with an experimental study on the structural behavior of bars supported on a helical cylindrical surface and subject to compressive loads. A special experimental apparatus was designed and built for this purpose. The design, as well as the adjustment of such an apparatus is described in details. The device allows one adjusting the bars by using a system consisting of a series of bearings that can be positioned to give freedom to the structure in two different directions: radial (normal to the cylindrical surface) and lateral (tangential or bi-normal). The compressive load is applied in the tangential direction of the helix. Bars with circular and rectangular cross sections, with various buckling lengths and different helix angles, were tested. Preliminary studies with straight bars, have allowed to evaluate the boundary conditions offered by the apparatus. In these cases, it was possible to induce the phenomenon of buckling, obtaining, consistently, the values of critical loads provided by the theory of Euler and to evaluate the boundary conditions provided by the apparatus. The use of a high-speed camera allowed to observe the phenomenon of instability. The structural behavior of curved bars of circular and rectangular sections was also studied. Both, the test free length as the helix angle were varied. The study enabled us to get a huge amount of experimental data about the behavior of helical bars, subjected such loading and boundary conditions. However, the phenomenon of instability could not be induced, for any condition tested. This fact could collaborate for further inferences about the study of the birdcaging instability at flexible pipes.

The deployment of engineering models and design methods divorced from the effect that mechanised shield tunnelling with tunnel boring machines (TBMs) has on concrete segmental linings (CSLs) can lead to either material waste or structural damage within the tunnel design life. Most research to date on CSL behaviour during construction neglects the sequential ring loading and TBM-lining transverse interactions, which this thesis proved to be key in the short and long term behaviour of CSLs and whose study is essential if the design and maintenance of CSL structures is ever to be optimised. This thesis investigates the longitudinal and transverse behaviour of CSL structures simultaneously backfilled with bicomponent grouts (BGs) during tunnelling, and how this early response influences long term behaviour. The research work is drawn on three pillars that enable cross-validation of conclusions: analytical models, three-dimensional numerical simulations and the interpretation of the Crossrail's Thames tunnel (CTT) field data, which included distributed fibre optic strain (DFOS) data. A theoretical framework ranging from construction loading scenarios to the mechanisms underlying structural damage is described for the future development of limit state design methods. Analytical models of longitudinal behaviour are also proposed. The study of joint geometries, temporary spear bolts and DFOS sensing in CSL construction monitoring is included as ancillary research. The solution developed for a sequential elastic rod subjected to a trilinear temperature profile and in shear interaction with the elastic ground predicts accurately the early tunnel pre-stressing relaxation caused by grout hardening, e.g. ≈50% in the CTT. The proposed sequential elastic beam model, which incorporates the effects of stage-varying net TBM moments, transverse loads and lining pressure gradients within the tunnel unsupported length, estimates satisfactorily the history of tunnel beam response during construction for a realistic expression of the lining stiffness. A potential damage assessment method for the early detection of tunnel sections prone to ring joint damage was proposed. The TBM-lining transverse interaction determines the CSL ring behaviour at the early stages of tunnelling. The ring response resultant from this interaction is irrecoverable and contributes to the long term total deformations and internal forces; in tunnels excavated in grounds with Ko≈1, it becomes the major source of ring distortion. The main transverse actions are the sealing pressures, which are inversely related to the tail clearance, and the transverse load of oblique hydraulic jacks. When the non-bedded rings are eccentric with respect to the shield tail, the ring distortion increases the risk of cracking near the rear corners and spalling at the ram pad interspaces of constrained segments. The ring distortion is directly related to the pressure gradients, the unsupported length and the ring flexibility. When individual segments rotate outwards under the action of transverse ram loads, e.g. the outer springline segment during pronounced TBM steering around a horizontal curve, the localised action of the sealing pressures can result in longitudinal cracking at the intrados of the segment front. This study represents a qualitative leap towards the optimisation of CSL design, shifting the attention of researchers and designers to TBM-lining transverse interactions as the most determinant factor of structural response during construction in CSLs simultaneously backfilled with BGs.

A presente dissertação trata do estudo experimental do comportamento estrutural de barras helicoidais assentadas sobre superfície cilíndrica e sujeitas a cargas de compressão. Aparato experimental específico foi projetado e construído para este fim. O projeto, bem como a aferição deste aparato, é descrito em detalhes. Este aparato permite ajustar as barras através de um sistema de apoios constituídos por uma série de rolamentos, que podem ser posicionados de forma a conferir liberdade de deslocamento à barra em duas direções distintas: radial (normal à superfície cilíndrica de assentamento) e lateral (tangencial; bi-normal). A aplicação de carga compressiva se faz na direção tangencial à hélice não-deformada. Barras com seção transversal circular e retangular, com diversos comprimentos livres de flambagem e para diferentes ângulos de assentamento, foram ensaiadas. Estudos preliminares, com barras retas, permitiram avaliar as condições efetivas de engastamento proporcionadas pelo aparato. Nestes casos foi possível induzir o fenômeno de flambagem, recuperando-se, consistentemente, os valores de cargas críticas previstas pela teoria de Euler e avaliando-se o grau de engastamento proporcionado pelo aparato experimental. Filmagem com câmera de alta velocidade permitiu observar o fenômeno de instabilidade. O comportamento estrutural das barras curvas, de seção circular e retangular, foi então estudado. Tanto o comprimento livre quanto o ângulo de assentamento foi variado. O estudo permitiu levantar base de dados experimentais do comportamento de barras helicoidais nessas condições de carregamento e de condições de contorno. No entanto, para nenhuma das diversas condições ensaiadas foi possível induzir o fenômeno de instabilidade. Tal fato poderia dar subsídios a inferências acerca do estudo da instabilidade de tubos flexíveis do tipo birdcaging. / This dissertation deals with an experimental study on the structural behavior of bars supported on a helical cylindrical surface and subject to compressive loads. A special experimental apparatus was designed and built for this purpose. The design, as well as the adjustment of such an apparatus is described in details. The device allows one adjusting the bars by using a system consisting of a series of bearings that can be positioned to give freedom to the structure in two different directions: radial (normal to the cylindrical surface) and lateral (tangential or bi-normal). The compressive load is applied in the tangential direction of the helix. Bars with circular and rectangular cross sections, with various buckling lengths and different helix angles, were tested. Preliminary studies with straight bars, have allowed to evaluate the boundary conditions offered by the apparatus. In these cases, it was possible to induce the phenomenon of buckling, obtaining, consistently, the values of critical loads provided by the theory of Euler and to evaluate the boundary conditions provided by the apparatus. The use of a high-speed camera allowed to observe the phenomenon of instability. The structural behavior of curved bars of circular and rectangular sections was also studied. Both, the test free length as the helix angle were varied. The study enabled us to get a huge amount of experimental data about the behavior of helical bars, subjected such loading and boundary conditions. However, the phenomenon of instability could not be induced, for any condition tested. This fact could collaborate for further inferences about the study of the birdcaging instability at flexible pipes.

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