137 research outputs found
Dissolution experiments of commercial PWR (52 MWd/kgU) and BWR (53 MWd/kgU) spent nuclear fuel cladded segments in bicarbonate water under oxidizing conditions. Experimental determination of matrix and instant release fraction
The denominated instant release fraction (IRF) is considered in performance assessment (PA) exercises to govern the dose that could arise from the repository. A conservative definition of IRF comprises the total inventory of radionuclides located in the gap, fractures, and the grain boundaries and, if present, in the high burn-up structure (HBS). The values calculated from this theoretical approach correspond to an upper limit that likely does not correspond to what it will be expected to be instantaneously released in the real system. Trying to ascertain this IRF from an experimental point of view, static leaching experiments have been carried out with two commercial UO2 spent nuclear fuels (SNF): one from a pressurized water reactor (PWR), labelled PWR, with an average burn-up (BU) of 52 MWd/kgU and fission gas release (FGR) of 23.1%, and one from a boiling water reactor (BWR), labelled BWR, with an average BU of and 53 MWd/kgU and FGR of 3.9%.; One sample of each SNF, consisting of fuel and cladding, has been leached in bicarbonate water during one year under oxidizing conditions at room temperature (25 +/- 5) degrees C. The behaviour of the concentration measured in solution can be divided in two according to the release rate. All radionuclides presented an initial release rate that after some days levels down to a slower second one, which remains constant until the end of the experiment. Cumulative fraction of inventory in aqueous phase (FIAPc) values has been calculated. Results show faster release in the case of the PWR SNF. In both cases Np, Pu, Am, Cm, Y, Tc, La and Nd dissolve congruently with U, while dissolution of Zr, Ru and Rh is slower. Rb, Sr, Cs and Mo, dissolve faster than U. The IRF of Cs at 10 and 200 days has been calculated, being (3.10 +/- 0.62) and (3.66 +/- 0.73) for PWR fuel, and (035 +/- 0.07) and (0.51 +/- 0.10) for BWR fuel. (C) 2015 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (author's final draft
Final overview of COST Action TU1406 – Quality control of existing bridges
Across Europe, the need to manage roadway bridges efficiently led to the development of multiple management systems. Despite presenting similar system frameworks, the condition assessment procedure is one of the difference that distinguishes them. This dissimilarity constitutes a divergent mechanism that has direct interference in the decision making process leading to considerable variations in roadway bridges quality. COST Action TU1406 aims to institute a standardized roadway bridges condition assessment procedure. Such purpose requires the establishment of recommendations for the quantification of performance indicators, the definition of performance goals and a guideline for the standardization of quality control plans for bridges. By developing new approaches to quantify and assess bridge performance, as well as quality specifications to assure expected performance levels, bridge management strategies will be significantly improved, enhancing asset management of ageing structures in Europe. The work developed and achieved by COST Action TU1406 will be presented.COST - European Cooperation in Science and Technology(undefined
On the robustness to corrosion in the life cycle assessment of an existing reinforced concrete bridge
Management of existing structures has traditionally been based on condition assessment, based on visual inspections, disregarding the susceptibility of different structural types to aging and deterioration. Robustness, as a measure of the effects of unpredictable damage to structural safety can be a complementary information to the results of inspection. Although robustness has mostly been used to evaluate the consequences of extreme events, a similar framework can be used to investigate the result of aging, allowing a better understanding of the potential effects of deterioration and allowing a better allocation of available maintenance funding. In this work, a probabilistic structural robustness indicator is used to quantify the susceptibility of structures to corrosion. The methodology is exemplified through a case study comprising an existing reinforced concrete bridge deck, heavily damaged due to reinforcement corrosion, and finally demolished due to safety concerns. Robustness measures the bridge deck safety tolerance to reinforcement corrosion. The principal effects of corrosion, including loss of area and bond between concrete and steel are modelled using a non-linear finite-element model, coupled with a Response Surface Method to compute the bridge reliability as a function of the corrosion level, and finally used to assess robustness. Results show that the redundancy of the bridge allows significant redistribution of loads between elements with different corrosion levels. As a result, the bridge presents significant robustness and tolerance to reinforcement corrosion
Evolución de la flexibilidad de la cadena cinética posterior en escolares de 5 a 11 años
La finalitat del nostre estudi Ă©s valorar l’evoluciĂł de la flexibilitat de la cadena cinètica posterior en els escolars de 5 a 11 anys, i observar en quins grups d’edat Ă©s necessĂ ria l’aplicaciĂł de programes especĂfics per a millorar-la. Els escolars varen ser sotmesos a les mateixes valoracions: el test de “sit and reach”, la pressa de les mesures antropomètriques, altura i pes, i el qĂĽestionari Minesotta sobre el consum calòric en el temps de lleure. Dels resultats es desprèn que a mesura que augmenta l’edat, la flexibilitat dels escolars estudiats disminueix progressivament. Existeix un interval d’edat situat en els 9 anys que sembla marcar un canvi de tendència en la
flexibilitat dels escolars. És a partir d’aquesta edat quan el grau de flexibilitat disminueix de forma significativa i, es mĂ©s marcada entre els nens, sent necessĂ ria una intervenciĂł mĂ©s especĂfica en ells
Temperature Effects Removal from Non-Stationary Bridge–Vehicle Interaction Signals for ML Damage Detection
The development of Structural Health Monitoring (SHM) and Non-Destructive Testing (NDT) techniques has rapidly evolved and matured over the past few decades. Advances in sensor technology have facilitated deploying SHM systems for large-scale structures and local NDT of structural members. Although both methods have been successfully applied to identify structural damage in various systems, Environmental and Operational Condition (EOC) variations can influence sensor measurements and mask damage signatures in the structural response. EOCs include environmental conditions, such as temperature, humidity, and wind, as well as operational conditions, such as mass loading, vibration, and boundary conditions. The effect of EOCs can significantly undermine the reliability and robustness of damage assessment technologies and limit their performance. Thus, successful SHM and NDT systems can compensate for changing EOCs. This paper provides a stateof-the-art review of the effects of EOCs on SHM and NDT systems. It presents recent developments
in advanced sensing technology, signal processing, and analysis techniques that aim to eliminate the masking effect of EOC variations and increase the damage sensitivity and performance of SHM and NDT systems. The paper concludes with current research challenges, trends, and recommendations
for future research directions
Programa de intervenciĂłn especĂfico para la mejora de la flexibilidad en escolares: es efectiva la intervenciĂłn del MEF?
La finalitat del nostre va ser valorar l’aplicaciĂł d’un programa d’intervenciĂł especĂfic per a millorar la flexibilitat en un grup d’escolars de 9 anys. Van ser inclosos en l’estudi 63 escolars de 4Âş curs d’EducaciĂł PrimĂ ria, del Centre Escolar la Salle i el CEIP St. Ignasi, ambdĂłs de Manresa (Barcelona). Durant tres setmanes, el centre La Salle va aplicĂ un programa especĂfic per a millorar la flexibilitat de la cadena cinètica posterior. En canvi, el CEIP St. Ignasi es va utilitzar com a grup control, continuant el seu programa educatiu habitual.
Hem observat que l’aplicaciĂł de programes especĂfics per a millorar la flexibilitat Ă©s efectiva en los escolares de 9 anys. La forma de aplicar els programes de educaciĂł fĂsica modifica significativament el grau de flexibilitat en los
escolares
A reliability-based measure of robustness for concrete structures subjected to corrosion
This work is a contribution to the definition and assessment of structural robustness. Special emphasis is given to reliability of reinforced concrete structures under corrosion of longitudinal reinforcement.
On this communication several authors’ proposals in order to define and measure structural robustness are analyzed and discussed. The probabilistic based robustness index is defined, considering the reliability index decreasing for all possible damage levels. Damage is considered as the corrosion level of the longitudinal
reinforcement in terms of rebar weight loss. Damage produces changes in both cross sectional area of rebar and bond strength. The proposed methodology is illustrated by means of an application example. In order to
consider the impact of reinforcement corrosion on failure probability growth, an advanced methodology based on the strong discontinuities approach and an isotropic continuum damage model for concrete is adopted. The methodology consist on a two-step analysis: on the first step an analysis of the cross section is performed in
order to capture phenomena such as expansion of the reinforcement due to the corrosion products accumulation and damage and cracking in the reinforcement surrounding concrete; on the second step a 2D deteriorated structural model is built with the results obtained on the first step of the analysis. The referred methodology
combined with a Monte Carlo simulation is then used to compute the failure probability and the reliability index of the structure for different corrosion levels. Finally, structural robustness is assessed using the proposed probabilistic index
Efficient implementation of finite volume methods in Numerical Relativity
Centered finite volume methods are considered in the context of Numerical
Relativity. A specific formulation is presented, in which third-order space
accuracy is reached by using a piecewise-linear reconstruction. This
formulation can be interpreted as an 'adaptive viscosity' modification of
centered finite difference algorithms. These points are fully confirmed by 1D
black-hole simulations. In the 3D case, evidence is found that the use of a
conformal decomposition is a key ingredient for the robustness of black hole
numerical codes.Comment: Revised version, 10 pages, 6 figures. To appear in Phys. Rev.
Robustness of corroded reinforced concrete structures. A structural performance approach
Structure and Infrastructure Engineering, 1-17The aim of this work is to provide new contributions in order to define more
accurately the structural robustness concept, particularly when applied to corroded reinforced concrete (RC) structures. To fulfill such task, several robustness indicators are analyzed and discussed with special emphasis on structural
performance based measures. A new robustness definition and a framework to assess it are then proposed, based on the structural performance lost after damage occurrence. The competence of the proposed methodology is then tested comparing the robustness of two reinforced concrete foot bridges under
corrosion. The damage considered is the longitudinal reinforcement corrosion
level and load carrying capacity is the structural performance evaluated. In order
to analyze corrosion effects, a finite element based on a two step analysis is
adopted. In the first step a cross section analysis is performed to capture phenomenons
such as expansion of the reinforcement due to the corrosion products accumulation; damage and cracking in the reinforcement surrounding concrete;
steel-concrete bond strength degradation; and effective reinforcement area reduction.
The results obtained are then used to build a 2D structural model, in order to assess the maximum load carrying capacity of the corroded structure.
For each foot bridge, robustness is assessed using the proposed methodology
A framework for robustness assessment in the context of corroded RC structures
Structural robustness is an emergent concept related to the structural response to damage. At the present time, robustness is not well defined and much controversy still remains around this subject. Even if robustness has seen growing interest as a consequence of catastrophic consequences due to extreme events, the fact is that the concept can also be very useful when considered on more probable exposure scenarios such as deterioration, among others. This paper intends to be a contribution to the definition of structural robustness, especially in the analysis of reinforced concrete structures subjected to corrosion. To achieve this, first of all, several proposed robustness definitions and indicators and misunderstood concepts will be analyzed and compared. From this point and regarding a concept that could be applied to most type of structures and dam-age scenarios, a robustness definition is proposed. To illustrate the proposed concept, an example of corroded reinforced concrete structures will be analyzed using nonlinear analysis numerical methods based on a contin-uum strong discontinuities approach and isotropic damage models for concrete. Finally the robustness of the presented example will be assessed.COST Action TU-0601; Fundação para Ciência e Tecnologi
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