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See detailExtension of the Direct Strength Method to hot-rolled and welded H profile cross-sections
Li, Yongzhen ULg

Doctoral thesis (2014)

The cross-sectional capacity is limited by material yielding on one hand and local buckling on the other hand. Most current metallic structural design codes use the concept of section classification for ... [more ▼]

The cross-sectional capacity is limited by material yielding on one hand and local buckling on the other hand. Most current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the classes 2 and 3 under pure bending load condition, while for the class 4, the effective width method (EWM) must be used to account for local buckling phenomenon. With the appearance of the more complex cross-sections, especially for thin-walled steel structures, the calculation using EWM becomes more and more intolerable and complicated. In order to overcome these difficulties when evaluating the cross-section strength, the alternative Direct Strength Method (DSM) approach, developed only for cold-formed thin-walled members, has gained importance over the last few years, and has been adopted by the North American and Australian standards for the design of cold-formed steel structural members recently. This thesis investigates the possibility to extend the DSM method to hot-rolled and welded structural steel members, and the objective is to derive a new formulation that would cover the whole field of section slenderness without section classification system used in Eurocode 3, using the same procedure for the DSM developed for cold-formed thin-walled steel structural members. Hot-rolled and welded H sections are mainly considered in this thesis. The DSM is premised on the assumption that the strength can be predicted from the yield strength to the elastic critical load ratio used in conjunction with a strength curve; i.e. the same concept than the one used in Eurocode 3, in terms of member buckling phenomenon. In the DSM approach applied for cold-formed thin-walled sections, local buckling and distortional buckling modes should be considered. For common hot-rolled or welded sections, only local buckling needs to be considered since distortional buckling does not occur for these sections. All available test results in literature are collected and evaluated with the current methods for calculating the cross-section resistance such as EWM, DSM, and the recent Continuous Strength Method (CSM). A short comparison is made and their domains of applicability are commented. A consistent approach has been adopted to develop numerical models for hot-rolled and welded sections subjected to compression and bending respectively. The FE model was built in FineLg and verified against test results of the “Semi-comp: Plastic member capacity of semi-compact steel sections - a more economic design” project, which was carried out earlier with the objective of improving the utilization of plasticity in rolled and welded sections with medium cross-section slenderness. Measured material and geometric properties, initial geometrical imperfections and residual stresses distributions have been highlighted. Once verified against the test results, the FE models have been used to carry out a parametrical study aimed at providing more FE results and highlighting the local buckling interaction between the webs and the flanges. All the experimental and FE numerical results constitute data base for the derivation of the new DSM curves. On the basis of Winter Formula for plate buckling and the generic DSM strength curve, different formulas are proposed for hot-rolled and welded H cross-sections under axial and bending load respectively. Also the statistical evaluation and safety study is conducted to obtain the safety factor γ_M, which is required for practical design. [less ▲]

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See detailNumerical Simulation of a Conical Shape Made by Single Point Incremental Forming
Velosa De Sena, José ULg; Duchene, Laurent ULg; Habraken, Anne ULg et al

in Incremental sheet forming (2014, May 08)

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See detailL'hypertension artérielle
Krzesinski, Jean-Marie ULg

Conference (2014, May 08)

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See detailLa régionalisation de l'IPP. Quel impact pour les communes ?
Husson, Jean-François ULg

Conference (2014, May 08)

Cette contribution évoque les problèmes et questions soulevées par la régionalisation de l'impôt des personnes physiques dans le cadre de la 6e réforme de l'Etat. Les questions liées au "fiscal mix" sont ... [more ▼]

Cette contribution évoque les problèmes et questions soulevées par la régionalisation de l'impôt des personnes physiques dans le cadre de la 6e réforme de l'Etat. Les questions liées au "fiscal mix" sont notamment abordées. [less ▲]

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See detailAbout almost periodic sequences of integers and related concepts
Crama, Yves ULg

Scientific conference (2014, May 07)

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See detailCOMPARISON AND MOLECULAR CHARACTERIZATION OF ANIMAL AND HUMAN CLOSTRIDIUM DIFFICILE STRAINS
Rodriguez Diaz, Cristina ULg; Taminiau, Bernard ULg; Korsak Koulagenko, Nicolas ULg et al

Poster (2014, May 07)

The main objective of this study was to characterize and compare animal and human C. difficile strains with respect to the PCR-ribotype and the antibiotic resistance. Multilocus sequence typing analysis ... [more ▼]

The main objective of this study was to characterize and compare animal and human C. difficile strains with respect to the PCR-ribotype and the antibiotic resistance. Multilocus sequence typing analysis (MLST) was performed in order to study clonal relationships of the isolates. [less ▲]

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See detailContributions à l’amélioration des systèmes d’évaluations génétiques
Vanderick, Sylvie ULg; Gengler, Nicolas ULg

Conference given outside the academic context (2014)

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See detailL'Etat congolais souverain ou sous-tutelle? Essai d'analyse de la dynamique politique nationale.
Baenda Fimbo, Zacharie ULg

Scientific conference (2014, May 07)

Après la définition de certains concepts tels que l'Etat, la souveraineté et la tutelle, la présente communication a analysé la dynamique politique congolaise à travers l'histoire. De la première ... [more ▼]

Après la définition de certains concepts tels que l'Etat, la souveraineté et la tutelle, la présente communication a analysé la dynamique politique congolaise à travers l'histoire. De la première république à la troisième. Des interventions étrangères ayant divisé les leaders politiques congolais pendant la première législative à la présence quasi permanente de la Communauté internationale à travers la Mission des Nations Unies au Congo, en passant par la deuxième république de Mobutu, les réalités locales laissent voir que certaines décisions politiques, voire certaines prises de position sont dictées de l'étranger. Les faits analysés fait douter l'applicabilité de la notion de souveraineté à la gestion politique de l'Etat congolais. [less ▲]

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See detailPolitiques institutionelles et migrations. Quelle place les institutions belges laissent-elles à la diversité ?
Grandjean, Geoffrey ULg

Conference given outside the academic context (2014)

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See detailLa Cour européenne des droits de l'homme
Habran, Maxime ULg

Scientific conference (2014, May 07)

Cette conférence vise à mettre en perspective la liberté d'expression dans le cadre des arrêts de la CEDH

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See detailAvancées récentes dans l'investigation olfactive de la mort
Stefanuto, Pierre-Hugues ULg; Focant, Jean-François ULg

Scientific conference (2014, May 07)

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See detailÉcrire les «petites langues»: entre transparence et universalisme
Baiwir, Esther ULg

Conference (2014, May 06)

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See detailL'astaxanthine: de la biologie à l'industrie
Fratamico, Anthony ULg

Scientific conference (2014, May 06)

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See detailStudy of the microbial flora of steak tartare by metagenomic approach
Korsak Koulagenko, Nicolas ULg; Delhalle, Laurent ULg; Nezer, Carine et al

Poster (2014, May 06)

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See detailHas oxygen depletion an impact on nutrients and macrofauna in a highly dynamic macrophytodetritus accumulation?
Remy, François ULg; Mascart, Thibaud ULg; Dauby, Patrick ULg et al

Poster (2014, May 06)

Posidonia oceanica is an endemic Mediterranean highly productive seagrass. Depending on the ability of the primary consumers to digest it alive, a generally important part of its foliar primary production ... [more ▼]

Posidonia oceanica is an endemic Mediterranean highly productive seagrass. Depending on the ability of the primary consumers to digest it alive, a generally important part of its foliar primary production falls in autumn, to decay inside the meadow or to be exported to sand patches to form “exported litter accumulations”. These accumulations are highly dynamic depending on hydrodynamics and seafloor geomorphology. Literature says that low O2 conditions might occur inside litter accumulations, but the annual oxygen dynamics or its impact on the litter-associated macrofauna has never been measured. We focused on 2 exported litter accumulations in Calvi Bay (Corsica), during 2 years for a total of 8 seasons. For each season, we collected water samples (n=6) from 3 different strata: Water Column (WC), Water Just Above the litter (WJA) and Water Inside the litter (WI). Oxygen was measured for each replicate using a Winkler-based automated routine for oxygen concentration measurements on micro-volumes. At the same time, nutrients concentrations (PO4, NH4, and NO2+NO3) were measured in WC, WJA and WI, but also in the Interstitial Water (IW) using a spectrophotometric continuous flow analyzer (adapted for low nutrients level in an oligotrophic environment). In parallel, macrofaunal (size >500µm) samples (n=3-6) were also collected, counted and identified to the specific level. Our results show significant differences between O2 concentrations/saturation from WI and the two other strata. Significant differences were detected between seasons, sites and years for WI which is the only stratum where really low O2 conditions can be observed. Significant differences were also detected between seasons for both WC and WJA but no differences between sites and years. On the other hand no significant differences were detected between WC and WJA. A similar observation was made for the nutrients at the annual, seasonal and spatial level. Moreover differences are also observed between the nutrients themselves. Our data shows no correlation between WI O2 concentrations and saturation, and global macrofauna abundance or biodiversity. Results are more contrasting at an individual specific level for the 4 most dominant species. For two amphipod species, Gammarella fucicola (55% of the global abundance) and Gammarus aequicauda, no significant correlations were detected between their abundance and O2. For the leptostracan species, Nebalia strausi, a significant negative correlation with O2 concentration was detected. For the last amphipod species, Melita hergensis, a significant positive correlation was observed. Our analyses also show significant correlations between WI O2 concentration/saturation, and WI / IW nutrients concentration. To conclude, this work shows that WI is a very particular and dynamic environment considering O2 concentration and saturation. Low O2 conditions can be observed in WI but never in WC or WJA showing that internal processes and relations with the sediment determine the O2 dynamics in WI and showing a potential “barrier” effect between WI and WC. Moreover O2 dynamics and its consequences may play a role in the nutrients dynamics and cycles. It is clear that faunal responses to low O2 conditions are not identifiable at a global community level. At a specific level, we show a more complex situation: some species do not seem to be impacted by low O2 conditions, but some present a significant positive, or a significant negative response. This shows the existence and complexity of species-dependent low O2 tolerance/adaptation, and the importance of a specific level data analyses to detect responses of dominant litter associated macro- invertebrates to O2 concentration and saturation variations. [less ▲]

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