On the influence of the steel-concrete bond model for the simulation of reinforced concrete structures using damage mechanics

International audienceWhen dealing with the simulation of reinforced concrete structures, the bond model between steel and concrete can become a key point if crack properties are studied. The interface between both materials is indeed partly responsible for stress transfer and consequently for the crack spacing and openings. In the context of finite element simulations using damage mechanics for concrete, the influence of the relation between steel and concrete is evaluated by comparing two solutions a perfect relation (same displacement at the interface) and a recently developed bond model (sliding allowed). The approaches are compared on a reinforced concrete tie, a bending beam and a shearing wall. The interest of including a fine description of the steel-concrete bond rather than a simple perfect relation between materials, regarding the simulation of local properties (crack openings especially) depends on the type of applications (loadings) and on the expected crack pattern (and/or distribution of steel)

A 3D beam element analysis for R/C structural walls

To analyse the real 3D functioning of a structure under seismic loading the dialogue between tests and numerical simulations is needed. Within the framework of the TMR-ICONS research program, dynamic and cyclic tests on U-shaped shear walls have been performed at CEA Saclay and JRC Ispra respectively. More recently, for the French program ìCAMUS 2000î, shaking table tests have been performed on reinforced concrete structural walls. In order to simulate these tests, 3D multi-fiber beam elements are used. Comparison with the experimental results shows the well matching and the limitations of the approach

Modélisation simplifiée pour l'endommagement des structures en béton arme sous sollicitations sévères

La simulation du comportement non-linéaire des voiles en béton armé soumis à des sollicitations sismiques est un problème prioritaire pour la communauté parasismique nationale et internationale. Les séismes récents à Kobe (Japon), Izmit (Turquie) et Athènes (Grèce) ont prouvé encore une fois le rôle primordial que tels éléments jouent pour la sécurité des ouvrages. Recevant la plus grande partie de l'effort sismique, les voiles conditionnent le comportement des structures à murs. Il est donc important de trouver des méthodes numériques adéquates pour simuler le comportement de différents types de voiles souvent rencontrés dans les bâtiments, les installations nucléaires etc. L'équipe « Modélisation des ouvrages sous sollicitations extrêmes » du Laboratoire de Mécanique et de Technologie (LMT) a depuis des années privilégié la recherche vers la mise au point de méthodes simplifiées, fiables et rapides pour le calcul du comportement non linéaire des structures. Pour des voiles ordinaires-élancement supérieur à 1.0-une stratégie de modélisation a été déjà proposée (Mazars et al 1999, Ragueneau 1999). La méthode consiste à utiliser des éléments poutres multicouches de type Bernoulli, capables de simuler le comportement des voiles, dominés par la flexion. La loi constitutive du béton est basée sur la mécanique de l'endommagement. Pour des problèmes de murs d'élancement voisin de 1.0 où le cisaillement est prépondérant, une approche nommée 1.5D a été développée (Dubé 1997). Dans ce cas, des poutres de type Timoshenko sont utilisées et le cisaillement est pris en compte par une contribution non-linéaire des contraintes de cisaillement dans la section. La méthode a été appliquée avec succès pour la modélisation de la maquette NUPEC (élancement 0.7)

Poutre multifibre Timoshenko pour la modélisation de structures en béton armé: Théorie et applications numériques

International audienceLes équations d'un élément poutre 3D multifibre Timoshenko et son utilisation pour la modélisation de structures en béton armé sont ici présentées. L'originalité de l'élément est qu'il a deux nœuds et des fonctions d'interpolation d'ordre supérieur pour éviter les problèmes lies au blocage par le cisaillement. Des exemples numériques comparés avec des résultats expérimentaux montrent la pertinence de l'approche

Couplage numérique et expérimental pour l’évaluation probabiliste des structures bois sous chargement sismique

This paper presents a two-step probabilistic approach to deal with problems involving high-dimensional input parameter spaces. Firstly, the effective stochastic dimension is identified using a screening method. The most important parameters are then modelled as random variables and the others are represented by their mean values. Then, the variability of the model response is evaluated by the decomposition method. This approach is used to assess the integrity of timber roofs of residential houses under seismic event. The seismic loading is modelled by real earthquake ground motion records representing the seismic hazard of the city of Le Moule in Guadeloupe. The variability of the damage accumulated in the structure is properly assessed by computing the statistical moments and the construction of the probability density. The results have shown that the uncertain parameters have significant effect on the variability of the damage accumulated in timber joints located on the bracing members. In addition, the damage variability and the PGA near-collapse are closely correlated. Finally, the probabilistic computation results have been used to construct fragility curves, which are very useful for the design of timber roof

A Feasibility Experiment of a W-powder Target

The development of high‐powertargetsremains a key R&D actvity for future facilities presently under study like the Neutrino Factory, Muon Collider or upgraded high‐power super beams for long‐baseline neutrino experiments. The choice of materials to sustain the beam power ranging up to MW levels is not trivial.Granular solid targets have been proposed and are being studied as a candidate for such high-power target systems. In the recently commissioned HiRadMat facility at CERN, a feasibility experiment of a tungsten powder target was performed. The experiment was designed to explore for first time the impact of a high‐power proton beam on a static W powder target in a thimble configuration. The diagnostics of the experiment were based on remote high‐speed photography as well as on laser‐doppler vibration measurements of the target containers. Results from the experimental findings are presented in this poster

A Very Intense Neutrino Super Beam Experiment for Leptonic CP Violation Discovery based on the European Spallation Source Linac: A Snowmass 2013 White Paper

Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spallation Source currently under construction in Lund, Sweden to deliver, in parallel with the spallation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spallation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few $\mu$s with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 $\sigma$ significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 $\sigma$ if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented.Comment: 28 page

High intensity neutrino oscillation facilities in Europe

The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fréjus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of μ+ and μ− beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular He6 and Ne18, also stored in a ring. The far detector is also the MEMPHYS detector in the Fréjus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive