Relative contributions of solid skeleton visco-plasticity and water viscosity to the poro-mechanics behavior of callovo-oxfordian claystone

The Callovo-Oxfordian claystone is a saturated porous medium. Its transfer properties, including its low permeability [16] make it an interesting candidate for underground radioactive waste disposal. The drained tests performed on the claystone, collected by ANDRA1 from samples at 500 meters depth [16, 9], exhibits a damageable visco-elasto-plastic behavior. This viscous behavior includes both the viscosity of the skeleton and the water. In existing models [5, 6, 11, 1], the creep phenomena are attributed either to the water permeability, to the skeleton visco-plasticity or sometimes both [13]. In a first step, a simplified analysis is proposed to understand the contribution of each phenomenon with respect to the consolidation time. This study indicates that the apparent characteristic time is the sum of those related to the skeleton and water permeability. To handle both non-linear and viscous phenomena, the damage law [15], coupled with the basic creep model [14] is used to characterize the solid skeleton of the claystone. The fluid behavior is integrated with the poro-mechanical model [7] implemented in the finite element code CAST3M [4]. The proposed model (visco-elastic damageable skeleton + saturating fluid) is used to simulate an excavation from the ANDRA underground laboratory (located in Bure–France). This application allows the understanding of how both viscous phenomena combine at each step of the calculation. Just after the excavation, water overpressure decreases near the gallery approaching zero due to the damage and then increases the permeability. The viscosity is then controlled by the solid skeleton creep rates. Later, the redistribution of hydraulic pressure is of more importance and permeability again plays a major role

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

Influence of interface zone behaviour in reinforced concrete under tension loading: an analysis based on modelling and digital image correlation

The problem of durability in reinforced concrete structures is a major case of concern nowadays. The problem of leakage due to cracking phenomena in critical structures such as nuclear power plants is specifically significant. In these structures, the number of cracks, their distribution and opening are needed to predict leakage possibilities. These variables depend on both the behaviour law of concrete and the behaviour law of steel-concrete interface. This article intends to compare experimental and modelling results focusing on interface zone between concrete and steel reinforcement. The first step consists in performing tests to capture behaviour of reinforced concrete prismatic elements subjected to pure tension. Crack opening along these structures is investigated by using digital image correlation (DIC), which allows the observation of crack propagation during loading. Next, the tension test of reinforced concrete is modelled in two different ways. Firstly, the connection zone between concrete and steel bar is assumed to be perfect (none-sliding connection). Then, a hypothesis of interface zone model between these two materials which allows plastic sliding [1], is considered. An orthotropic model of concrete based on plasticity and damage theories is used for this modelling. The model is able to predict crack opening and manage its reclosure [2]. Finally, results of the test are compared to the both modelling. A discussion concerning the need of interface model finishes this paper

Numerical modelling for earthquake engineering: the case of lightly RC structural walls

Different types of numerical models exist to describe the non‐linear behaviour of reinforced concrete structures. Based on the level of discretization they are often classified as refined or simplified ones. The efficiency of two simplified models using beam elements and damage mechanics in describing the global and local behaviour of lightly reinforced concrete structural walls subjected to seismic loadings is investigated in this paper. The first model uses an implicit and the second an explicit numerical scheme. For each case, the results of the CAMUS 2000 experimental programme are used to validate the approaches

Diet of Adélie penguins (<i>Pygoscelis adeliae</i>) at Stranger Point (25 de Mayo/King George Island, Antarctica) over a 13-year period (2003–2015)

Knowledge of the feeding ecology of a species at local level is fundamental to determine the relationship between the fluctuations in local marine resources and population dynamics of predators. In this study, we examined the diet of Adélie penguins (Pygoscelis adeliae) during the crèche stage at the Stranger Point colony, South Shetland Islands, Antarctica, over a 13-year period (2002/2003–2014/2015). Antarctic krill (Euphausia superba) was the dominant prey for Adélie penguins during the crèche period (contribution: 100% of occurrence and >99.7% by mass). The fish component in the diet represented a small proportion of the total prey (contribution: from 4 to 24% of occurrence but <0.15% by mass). A marked inter-annual variability in the mass of stomach contents, the krill size consumed and the proportion of juvenile krill was observed. Moreover, a possible recruitment event of krill was recorded. A negative relationship between the size of krill in the diet and breeding success was found, suggesting that population dynamics of krill also reflected changes in the local availability of this crustacean. This work is the first long-term study of dietary parameters of Adélie penguins for the Stranger Point colony.Facultad de Ciencias Naturales y Muse

Lanternfish (Myctophidae) in the diet of the Cape petrel Daption capense at the South Shetland and South Orkney Islands, Antarctica

All of the fish identified in stomach contents and regurgitations of breeding and chick Cape petrels collected during January and February 1996 at Fildes Peninsula and Harmony Point, both in the South Shetland Islands and at Laurie Island, South Orkney Islands, were myctophids, a family never previously reported in the diet of breeding Cape petrels. Electrona antarctica was the most important fish prey, followed by Electrona carlsbergi at Fildes Peninsula, Krefftichthys anderssoni at Harmony Point and Gymnoscopelus braueri at Laurie Island. The absence of Pleuragramma antarcticum in the diet of this petrel, which is considered a P. antarcticum-feeder, is discussed

Relative contributions of solid skeleton visco-plasticity and water viscosity to the poro-mechanics behavior of callovo-oxfordian claystone

The Callovo-Oxfordian claystone is a saturated porous medium. Its transfer properties, including its low permeability [16] make it an interesting candidate for underground radioactive waste disposal. The drained tests performed on the claystone, collected by ANDRA1 from samples at 500 meters depth [16, 9], exhibits a damageable visco-elasto-plastic behavior. This viscous behavior includes both the viscosity of the skeleton and the water. In existing models [5, 6, 11, 1], the creep phenomena are attributed either to the water permeability, to the skeleton visco-plasticity or sometimes both [13]. In a first step, a simplified analysis is proposed to understand the contribution of each phenomenon with respect to the consolidation time. This study indicates that the apparent characteristic time is the sum of those related to the skeleton and water permeability. To handle both non-linear and viscous phenomena, the damage law [15], coupled with the basic creep model [14] is used to characterize the solid skeleton of the claystone. The fluid behavior is integrated with the poro-mechanical model [7] implemented in the finite element code CAST3M [4]. The proposed model (visco-elastic damageable skeleton + saturating fluid) is used to simulate an excavation from the ANDRA underground laboratory (located in Bure–France). This application allows the understanding of how both viscous phenomena combine at each step of the calculation. Just after the excavation, water overpressure decreases near the gallery approaching zero due to the damage and then increases the permeability. The viscosity is then controlled by the solid skeleton creep rates. Later, the redistribution of hydraulic pressure is of more importance and permeability again plays a major role

Influence of interface zone behaviour in reinforced concrete under tension loading: an analysis based on modelling and digital image correlation

The problem of durability in reinforced concrete structures is a major case of concern nowadays. The problem of leakage due to cracking phenomena in critical structures such as nuclear power plants is specifically significant. In these structures, the number of cracks, their distribution and opening are needed to predict leakage possibilities. These variables depend on both the behaviour law of concrete and the behaviour law of steel-concrete interface. This article intends to compare experimental and modelling results focusing on interface zone between concrete and steel reinforcement. The first step consists in performing tests to capture behaviour of reinforced concrete prismatic elements subjected to pure tension. Crack opening along these structures is investigated by using digital image correlation (DIC), which allows the observation of crack propagation during loading. Next, the tension test of reinforced concrete is modelled in two different ways. Firstly, the connection zone between concrete and steel bar is assumed to be perfect (none-sliding connection). Then, a hypothesis of interface zone model between these two materials which allows plastic sliding [1], is considered. An orthotropic model of concrete based on plasticity and damage theories is used for this modelling. The model is able to predict crack opening and manage its reclosure [2]. Finally, results of the test are compared to the both modelling. A discussion concerning the need of interface model finishes this paper

Enhanced 3D multifibre beam element accounting for shear and torsion

The purpose of this work is to investigate solutions for an enhanced multifibre beam element accounting for non-linear shear and torsion. Higher order interpolations functions are used to avoid any shear locking phenomena and the cross section warping kinematics are extended to non-linear behavior using advanced constitutive laws. The efficiency of the proposed modeling strategies is tested with experimental results of reinforced concrete structural elements subjected to severe loading