Modeling of steel and concrete strains between primary cracks for the prediction of cover-controlled cracking in RC-beams

After cracking, the intact concrete between two consecutive primary cracks remains elastic and the maximum concrete stress is less than the tensile strength of concrete. However, under increasing loading, cover-controlled cracks occur at the steel-concrete interface causing a loss of bond and hence a loss of tension stiffness. The cover-controlled cracks are internal concrete cracks that initiate at steel rib location and are contained within the concrete cover. In this paper, steel and concrete strain distribution between two consecutive primary cracks are modeled based on a linear assumed distribution of the bond stress at the steel-concrete interface. The accurate calculation of the tensile concrete strain allows introducing new criteria for cover-control cracking initiation based on a peak value of steel stress calculated at crack location.     

Analyse qualitative et quantitative des erreurs en métrologie thermique par la méthode de la plaque chaude gardée —cas des matériaux homogènes

Résumé Les expériences relatées dans cet article sont destinées à mettre en évidence, qualitativement et surtout quantitativement, les erreurs accidentelles et systématiques commises lors de la mesure du coefficient de conductivité apparent moyen des matériaux homogènes, faiblement conducteurs, par la méthode de la plaque chaude gardée. Outre l'importance de la qualité de la cha?ne de mesure, l'accent est mis sur les erreurs introduites par les lames d'air aux interfaces et la position relative des capteurs de température ainsi que celles résultant des déviations des lignes de flux situées dans la zone de mesure.

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Summary The experiments reported in this article aim at underlining, qualitatively and especially quantitatively, the accidental and systematic errors occurring during measurement of the mean apparent conductivity coefficient in homogeneous materials of low conductivity using the guarded hot plate method. Apart from the importance of the quality of the measuring chain, emphasis is placed on the errors caused by thin layers of air at interfaces and the relative location of temperature transducers, as well as errors brought about by flux line diversions in the measuring area.