DIMM-Comunicaciones a Congresos, Conferencias...
URI permanente para esta colecciónhttps://hdl.handle.net/10953/245
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Examinando DIMM-Comunicaciones a Congresos, Conferencias... por Materia "Cohesive Fracture"
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Ítem Numerical modelling of fracture in polyolefin fibre reinforced concrete specimens under mixed-model loading (I+II)(2019-06) Suárez-Guerra, Fernando; Gálvez-Ruíz, Jaime Carlos; Enfedaque, Alejandro; García-Alberti, MarcosIn the last decades, many researchers have focused their work on studying the behaviour of fibre-reinforced concrete (FRC). The appearance of specific recommendations in several Standards has boosted their usage and the interest in this technology. Apart from the traditional steel fibres, new materials are now studied as fibre-type reinforcement in structural concrete. This is the case of polyolefin, a polymer that has proved to be a suitable alternative that overcomes some of the drawbacks of steel, namely those related to corrosion processes, and keeps a good ductile behaviour providing structural strength to concrete against tensile stresses. Modelling fracture of FRC elements has also proved to be successful using trilinear softening functions, not only with polyolefin fibres, but also with steel and glass fibres. Nevertheless, these numerical models have been used to contrast only notched specimens under three-point bending symmetric loading. In this contribution, trilinear softening functions are used to model fracture in specimens in which crack initiates under a combination of modes I and II. Fracture is modelled by means of an embedded crack formulation based on the strong discontinuity approach. Two sets of experimental data are compared, one with specimens of the same size with different proportions of fibres and another one where, keeping the fibre proportion constant, the specimens are scaled up in order to analyse the size effect. In both sets of experimental results, the Load-CMOD diagrams fit reasonably well using trilinear softening functions, predicting with correction the maximum load and the shape of the diagram due to the influence of the fibres.Ítem On the numerical modelling of punching shear in flat reinforced concrete slabs by means of the finite element method(2025-04) Suárez-Guerra, Fernando; Gálvez-Ruíz, Jaime CarlosThe slab-column connection is a critical point in the design of a structure, mainly buildings, since a high concentration of shear stresses can lead to punching, which is a localised failure mode that can take place in a brittle manner and with no previous warning. Currently, structural standards provide recommendations and general expressions to help design these structural connections, where the Critical Shear Crack Theory (CSCT), proposed by Muttoni, stands out. This approach considers the shear strength as dependent on the crack width developing in the shear-critical region and uses a control perimeter ($b_0$) that delimits the cracking region. Many efforts have been devoted to understanding the failure mechanisms involved in punching and to propose tools, such as CSCT, for a safe and efficient design; nevertheless, there is still no consensus on the mechanics governing this phenomenon. The present contribution uses the finite element method and takes advantage of material models based on continuum damage mechanics to reproduce punching failure in reinforced concrete slabs. This approach is not new and has been employed in the past, but with limitations and some issues still not completely solved. The aim of this work is to analyse different possible modelling techniques in order to obtain a numerical model that reproduces this phenomenon with accuracy. A major advantage of using a finite element model in this case is that the main fracture mechanisms involved in the failure process, which are varied and complex, can be identified. Bidimensional and tridimensional models are discussed, and the possibility of taking into account the slip between concrete and the reinforcement bars, which turns out to be a key mechanism in the evolution of punching failure, is analysed.