Examinando por Autor "Gálvez, Jaime C."
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Ítem A material model to reproduce mixed-mode fracture in concrete(Wiley, 2018-08) Suárez Guerra, Fernando; Gálvez, Jaime C.; Cendón , David A.This paper presents a material model to reproduce crack propagation in cement-based material specimens under mixed-mode loading. Its numerical formulation is based on the cohesive crack model, proposed by Hillerborg, and extended for the mixed-mode case. This model is inspired by former works by Gálvez et al but implemented for its use in a finite element code at a material level, that is to say, at an integration point level. Among its main features, the model is able to predict the crack orientation and can reproduce the fracture behaviour under mixed-mode fracture loading. In addition, several experimental results found in the literature are properly reproduced by the model.Ítem Damage tolerance in engineering components: Implementation to anchor heads(Elsevier, 2022-06) Olivares, Miguel A.; Gálvez, Jaime C.; Suárez Guerra, FernandoDamage tolerance is commonly used as a design criterion in some engineering fields, such as aerospace engineering, but is not usual in civil engineering, where structural safety often relies on safety coefficients. This work presents a study on how using damage tolerance for designing post-tensioning anchor heads, usual mechanisms in many civil engineering works, can be useful for building safer structures. Damage is simulated using 2D and 3D finite element models, considering axisymmetric damage and single damage, respectively. The influence of several aspects, such as the crack depth, the crack orientation angle or the shape of the anchorage, is studied. Lastly, a specific anchorage geometry is analysed using the damage tolerance concept to show that this approach may help in the design of this type of elements.Ítem Macro Photography as an Alternative to the Stereoscopic Microscope in the Standard Test Method for Microscopical Characterisation of the Air-Void System in Hardened Concrete: Equipment and Methodology(MDPI, 2018-08) Suárez Guerra, Fernando; Conchillo, José J.; Gálvez, Jaime C.; Casati, María J.The determination of the parameters that characterize the air-void system in hardened concrete elements becomes crucial for structures under freezing and thawing cycles. The ASTM C457 standard describes some procedures to accomplish this task, but they are not easy to apply, require specialised equipment, such as a stereoscopic microscope, and result in highly tedious tasks to be performed. This paper describes an alternative procedure to the modified point-count method that is described in the Standard that makes use of macro photography. This alternative procedure uses macro-photographic images that can be obtained with a quite standard photo camera and it is successfully applied to a large set of samples and presents some advantages over the traditional method, since the required equipment is less expensive and provides a more comfortable and less tedious procedure for the operator.Ítem Modelo de fractura en modo mixto (I y II) para materiales cementicios(2018-03) Suárez Guerra, Fernando; Cendón, David A.; Gálvez, Jaime C.Durante las pasadas décadas se ha dedicado un gran esfuerzo a la simulación de la fractura de materiales cuasifrágiles, como el hormigón. Muchos de los modelos propuestos se basan en el concepto de fisura cohesiva, habitualmente formulados en base a un comportamiento de rotura en modo predominantemente I, con un papel muy débil de las tensiones de cortante (modos II y III). En esta contribución se propone un modelo de material para simular la rotura en materiales de base cemento sometidos a estados de carga mixtos que combinan los modos de rotura I y II. La formulación propuesta se basa en el modelo de fisura cohesiva, extendida al caso de rotura en modo mixto, con un modo II significativo. El modelo se inspira en trabajos anteriores de Gálvez et al., pero, frente a ellos, aquí la rotura se formula a nivel de material, es decir, a nivel de los puntos de integración en un análisis con elementos finitos. A diferencia de trabajos anteriores, en los que la rotura se modelizaba mediante elementos intercara, el modelo propuesto es capaz de reproducir el camino de rotura sin información previa sobre el mismo.