Combined sticking: a new approach for finite-amplitude Coulomb frictional contact

Engineering-level accuracy of discretization methods for frictional contact originates from precise representation of discontinuous frictional and normal interaction laws and precise discrete contact techniques. In terms of discontinuous behavior in the quasi-static case, two themes are of concern: the normal interaction (i.e. impact) and the jumps in tangential directions arising from high frictional values. In terms of normal behavior, we use a smoothed complementarity relation. For the tangential behavior, we propose a simple and effective algorithm, which is based a stick predictor followed by corrections to the tangential velocity. This allows problems with impact and stick-slip behavior to be solved with an implicit code based on Newton–Raphson iterations. Three worked examples are shown with comparisons with published results. An extension to node-to-face form in 3D is also presented

Contamination, risk, and source apportionment of potentially toxic microelements in river sediments and soil after extreme flooding in the Kolubara River catchment in Western Serbia

Climate change is contributing to an increase in extreme weather events. This results in a higher river flooding risk, causing a series of environmental disturbances, including potential contamination of agricultural soil. In Serbia, the catastrophic floods of 2014 affected six river basins, including the Kolubara River Basin, as one of the larger sub-catchments of the large regional Sava River Basin, which is characterized by large areas under agricultural cultures, various geological substrates, and different types of industrial pollution. The main aim of this study was to establish the sources of potentially toxic elements in soil and flood sediments and the effect of the flood on their concentrations. Field sampling was performed immediately after water had receded from the flooded area in May 2014. In total, 36 soil samples and 28 flood sediment samples were collected. After acid digestion (HNO3), concentrations of the most frequent potentially toxic elements (PTE) in agricultural production (As, Cd, Cr, Cu, Ni, Pb, Zn) and Co which are closely related to the geological characteristics of river catchments, were analyzed. The origin, source, and interrelations of microelements, as well as BACKGROUND: values of the PTE of the river catchment, the pollution index (Pi), enrichment factor (Ef), and geological index (Igeo), were determined, using statistical methods such as Pearson correlations, principal component analysis (PCA), and multiple linear regression (MLRA). The content of the hot acid-extractable forms of the elements, PCA, and MLRA revealed a heavy geological influence on microelement content, especially on Ni, Cr, and Co, while an anthropogenic influence was observed for Cu, Zn, and Cd content. This mixed impact was primarily related to mines and their impact on As and Pb content. The pseudo-total concentrations of all the analyzed elements did not prove to be a danger in the catchment area, except for Cu in some samples, indicating point-source pollution, and Ni, whose pseudo-total content could be a limiting factor in agricultural production. For the Ef, the Ni content in 59% soil and 68% flood sediment samples is classified into influence classes. The similar pseudo-total contents of the elements studied in soil samples and flood sediment and their origin indicate that the long-term soil formation process is subject to periodic flooding in the Kolubara River Basin without any significant changes taking place. This implies that floods are not an endangering factor in terms of the contamination of soil by potentially toxic elements in the explored area

Rapport V.17 :Etude de protection de la Loire Moyenne par écrêtement des crues de l’Ailier

Possible systems of one or more flood-control dams in the Allier river basin are identified and compared, so as to answer the following question : " Would it be possible to ensure the same level of protection of the "Loire Moyenne" Valley with upstream dams as with the Veurdre project, taking into account real-time operating constraints ? After a comprehensive search for potential sites, the comparison with the Veurdre project, of the upstream solutions appearing best both for control of exceptionnal floods and for impacts limitation, shows that the latter do not provide satisfactory alternatives for the "Loire moyenne" Valley protection.L'étude a consisté à rechercher et comparer des systèmes d'un ou plusieurs barrages écrêteurs dans le bassin de l'Ailier, afin de répondre à la question suivante : "Serait-il possible d'assurer une protection de la vallée de la Loire Moyenne équivalente à celle qu'apporterait le projet du Veurdre, au moyen d'ouvrages sur le cours amont de l'ALLIER et de ses affluents, compte-tenu notamment des contraintes de gestion opérationnelle d'un tel ensemble ? Après une recherche systématique de sites potentiels, la comparaison avec le Veurdre des solutions apparaissant les meilleures sur le double plan de l'écrêtement des crues exceptionnelles et de la limitation des impacts négatifs, a conduit à la conclusion que celles-ci ne pouvaient constituer des alternatives viables pour la protection de la Loire Moyenne.Cappelaere Bernard, Grassin J., Gasowski Zbigniew, Raous P. Rapport V.17 :Etude de protection de la Loire Moyenne par écrêtement des crues de l’Ailier. In: L'impact des activités humaines sur les eaux continentales. Dix neuvièmes journées de l'hydraulique - Question I, II, III, IV, V et Compte rendu des séances. Tome 5, 1986

Modeling the interfaces in masonry structures

International audienceThis chapter deals with some models for interfaces in the case of masonry structures. Some experimental studies are recalled in the first part. In the second part, four interface models are presented