Author(s)

P. Procházka & N. Starikov

Abstract

In the problem of cracking of composite structures of several sorts, the pullout problem has frequently been solved. In some previous papers by the authors, curvilinear fibers reinforcing concrete mainly during its curing process have been studied. It was shown that the fibers of Dramix type proved to have a higher local bearing capacity than the straight fibers. The problem was solved in 3D on a unit cell assuming a periodicity of fiber placing. The linear behavior of concrete was taken into account and the pullout test was simulated by the finite element method. In this paper the optimal slope of fibers is sought. Using similar computations as those which were carried out in the above-mentioned papers, the optimum conditions have been added. They obey the typical Mohr-Coulomb law along the fiber-concrete interfacial zones and the compressive strength in the concrete cannot be exceeded at any point. The study is carried out on different unit cells, i.e. different positioning of fibers is considered. A different fiber ratio is also considered to show the mechanical behavior and to limit analysis of the composite aggregate. 1 Introduction In many branches of structural engineering fiber reinforced concrete has been used with different types of fibers. Because this study was financially supported from a grant project, which is concentrated on geomechanical structures, principally on reinforcement of tunnel linings and foundations, the steel fibers are considered in this paper. They play very important role particularly during curing process of concrete, as they suppress local cracking and warping in the composite structure and avoid a possibility of corrosion of reinforcing steel rods. Very important fact follows from plenty of experimental studies: since the steel fibers are more stiff then concrete itself, pullout problem has to be solved when

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