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22. Experimental and numerical investigation of restrained shrinkage of concreteLucija Hanžič, Jurij Karlovšek, Tomaž Hozjan, Sabina Huč, Zhongyu Xu, Igor Planinc, Johnny Ching Ming Ho, 2020, published scientific conference contribution Abstract: To promote the understanding of shrinkage related behaviour of concrete used for tunnel linings the experimental and theoretical investigation including numerical and analytical approach was performed on ring-shaped specimens. Overall one analytical (an.) and two numerical models, namely (i) and (ii) were also developed. Models (an.) and (i) considered the restraining steel ring to be rigid, thus not exhibiting any deformation. Numerical model (ii) considered the steel ring to be deformable. The experimental set-up consisted of a large concrete ring with an inner diameter of 120 cm, an outer diameter of 160cm and 20 cm in height. The restraining steel ring was 5.5 cm thick. Two concrete rings were made, namely R1 with a low compressive strength of ~26MPa and the other, R2, with medium compressive strength of ~40 MPa. The strain was measured in the hoop direction on the inner circumference of the steel ring and on the outer circumference of the concrete ring. Concrete rings were subjected to circumferential drying. Numerical model (ii) predicted critical time to the formation of the first crack to be between 13 and 14 days. The experimentally determined critical time is found to be 11 to 13 days with cracks gradually opening over several days. This was indicated by changes in measured concrete and steel strain. Modelled concrete strain just before cracking was between -20 and -30 % 10-6 m m-1 however, measured concrete strain was ~150 % 10-6 m m-1. Modelled steel strain was between -30 and -40 % 10-6 m m-1 while measured steel strain was between -10 and 20 % 10-6 m m-1. These discrepancies, in particular the positive steel strain obtained in experiments, require further investigation and improvements of the experimental set-up.
Keywords: concrete, tunnel lining, restrained shrinkage, Reissner beam theory, modelling
Published in DiRROS: 19.01.2024; Views: 528; Downloads: 217
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25. Biological behaviour of lung carcinoids : a retrospective analysis of 71 patientsIzidor Kern, Tomaž Rott, Marija Zupančič, Jurij Šorli, Urška Gantar-Rott, Janez Eržen, Janez Orel, Bogo Hrabar, 1994, professional article Keywords: rak (medicina), pljuča, pljučni rak, novotvorbe
Published in DiRROS: 11.01.2024; Views: 419; Downloads: 134
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