Creep and shrinkage modelling of HPC based on the evolution of the degree of hydration and the internal relative humidity

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Long-term behavior of a steel-concrete composite railway bridge deck

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Crack propagation in grooved long bone segment

International audienceThe following paper is an english translation of the scientific article "T. Kurtz, Y. Godio-Raboutet, and J.-L. Tailhan. Propagation de fissure sur tronçon d'os long rainuré. 25 ème congrès français de mécanique, nantes, france. 2022." [1]. The original version is published in french along the work presented during the 25 th French Congress of Mechanics in Nantes (from August 29 th to September 2 nd of 2022).URL link to the original article : https://hal.science/hal-04280203v1A mechanical test of macrocrack propagation in a cortical bone shaft is developed to comprehend the failure mechanisms at this scale and identify fracture processes, which are paramount to a future modelisation. A first set of three-point bending tests was performed on notched segments of human femoral dyaphisis [2, 3]. However, macrocrack orientation is influenced by the material’s anisotropy. In order to drive cracking processes in the transversal direction only, a modification of the testing protocol is submitted.From work found in the litterature [4, 5], notched shafts are previously grooved : a hemispherical groove is milled on the external surface of the bone to guide the crack in the transversal direction in the notch section. Special care is taken for the three-point bending test allowing a mastered procedure despite geometric variability of specimens : positioning and boundary conditions of the samples, notch displacement sensor’s supports alignment regarding bone axis, positioning and height of the notch, constant groove’s depth. The hydraulic jack is driven indirectly with the notch opening, measured with an inductive displacement sensor. A series of unloading/reloading cycles are done to plot residual quantities, pre-peak damage and macrocrack propagation in post-peak.Obtained results are expressed in terms of loading as a function of the notch opening displacement. Load-unloading cycles and residual openings analysis highlight the prominent role of cracking in failure mechanisms. Results show that the residual opening is directly linked to a structural weakening, consequently to the cracking processes, and that no plasticity is found at this scale. Cycles analysis allows us to develop a hypothesis about the role of internal residual stresses on permanent deformation. Furthermore, results point out that the groove guides the macrocrack in the transversal direction. Comparison between results on non-grooved samples exhibits the impact of the geometric feature. Future perspectives rely on the reverse analysis determination of the mechanical properties in the transversal direction

Creep and shrinkage of HPC in prebended composite structures. Part I: modelling

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Creep and shrinkage of HPC in prebended composite structures. Part II: in situ case study

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Experimental study of a macrocrack propagation in a concrete specimen subjected to creep loading

Structures managers need a better prediction of the delayed failure of concrete structures, especially for very important structures like nuclear power plant encasement. Sustained loadings at high level (above 75% of loading capacity of the structure), can lead to structure failure after some time. In this study, a series of 4-point bending tests were performed in order to characterize the creep behaviour of pre-cracked beams under high load level. The specimens were made of normal strength concrete. A power law relationship is observed between the secondary deflection creep rate and the failure time. It is also shown that when crack propagation occurs during the creep loading, the creep deflection rate increases with the creep loading level and with the crack propagation rate