Chapter 1 Influence of Fracture and Delayed Effects on Steel-Concrete Composite Structures Fery Léo, Gwozdziewicz Piotr, and Moutou Pitti Rostand Abstract This work investigates the fracture behavior of preflex beams submitted to time-dependent effects and long-term loadings. However, it is necessary to consider delayed effects such as shrinkage and creep on these structures because their influence is not negligible. The different materials used in mixed construction are presented. The flowchart applied to compute creep and relaxation effects versus the time is also described. It is interesting to note that the analytical results obtained for a preflex beam are very similar to those obtained using finite element modeling on the LUSAS software. It is also observable that the cracking of the concrete that encases the lower fiber, due to creep, causes an increase of stresses in the steel profile, which can break the beam. The use of reinforcement on the preflex beam decreases the crack opening after 100 years loadings. Keywords Steel-concrete composite structure · Creep · Shrinkage · Fracture · Preflex beam 1.1 Introduction Mixed construction is a method which knows a quick development and takes advantage of two materials: steel and concrete [1, 2]. They are linked together by connectors, so that concrete works in compression and steel in tension. This results in a composite beam with improved mechanical characteristics because both concretes are supposed to work in compression. However, it is necessary to consider the impact of delayed effects such as shrinkage and creep on the fracture processes of these structures because their influence is not negligible. The literature background shows that some authors discussed about the behavior and the manufacturing process of preflex beams [3, 4]. Foort [5] studied the behavior of connectors in preflex beams due to normal and rupture force. Jerome [6] investigated the cracking of stressed preflex beams by comparing numerical and analytical results given by the Ghali and Fabre method [7]. But the impact of delayed effects as creep and relaxation of crack process have not been investigated in this chapter. The different materials used in mixed construction are presented. At the same time, the conception step of the preflex beam and the numerical flowchart to obtain crack opening are described. It is also observable that the cracking of the concrete that encases the lower fiber, due to creep, causes an increase of stresses in the steel profile, which can lead to the total collapse of the beam. F. Léo Université Clermont Auvergne, CNRS, Institut Pascal, Clermont-Ferrand, France G. Piotr Facukty of Civil Engineering, Politechnika Krakowska, Warszawska, Krakow, Poland e-mail: pgwozdziewicz@pk.edu.pl M. P. Rostand ( ) Université Clermont Auvergne, CNRS, Institut Pascal, Clermont-Ferrand, France Institut de Recherche Technologique, CENAREST, Libreville, Gabon e-mail: rostand.moutou_pitti@uca.fr © The Society for Experimental Mechanics, Inc. 2021 S. Xia et al. (eds.), Fracture, Fatigue, Failure and Damage Evolution, Volume 3, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-60959-7_1 1
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