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As part of this study, has been developed a numerical method which allows to establish abacuses connecting the normal force with bending moment for a circular section and therefore to predict the rupture of this type of section. This may be for reinforced concrete (traditional steel) or concrete reinforced with steel fibers. The numerical simulation was performed in nonlinear elasticity up to exhaustion of the bearing capacity of the section. The rupture modes considered occur by plasticization of the steel or rupture of the concrete (under compressive stresses or tensile stresses). Regarding the fiber-reinforced concrete, the rupture occurs, usually, by tearing of the fibers. The behavior laws of the different materials (concrete and steel) correspond to the real behavior. The influence of several parameters was investigated, namely; diameter of the section, concrete strength, type of steel, percentage of reinforcement and contribution of concrete in tension between two successive cracks of bending. A comparison was made with the behavior of a section considering the conventional diagrams of materials; provided by the BAEL rules. A second comparative study was performed for fibers reinforced section.

This work is a part of an industrial waste development program. It is devoted to the study of recyclability of chips resulting from the machining of steel parts as reinforcement for concrete. We are particularly interested in this study in the rheological behavior of chips reinforced fresh concrete and its mechanical behavior at young age. The evaluation of the workability indicates that the sand over gravel optimal ratios (S/G), corresponding to the composite minimum flow time, are S/G = 0.8 and S/G = 1. The study of the chips content (W) influence on the workability of the concrete shows that the flow time and the optimal ratio S/G increase with W. Mechanical characterization tests (direct tension, compression, bending and splitting) show that mechanical properties of chips reinforced concrete are comparable to those of the two selected reference concretes (concrete reinforced with conventional fibers: EUROSTEEL fibers corrugated and DRAMIX fibers). Chips provide to control concrete a significant increase in strength and some ductility in the post-failure behavior of the composite. Recycling chips as reinforcement for concrete could be thus favorably considered.

The damage mechanics allows a detailed modeling of reinforced concrete’s degradation phenomenon. The theory of isotropic damage leads to quite satisfactory results in the description of both in the local and the global behavior. It is within the scope of this work to provide a model of damage based on the non-linear mechanical behavior of fiber concrete. This model takes into account the ductile nature of the observed during testing of material and direct tension after cracking. The modeling will be done while checking the principles of damage mechanics using the fundamentals of continuous mechanics of materials to propose a law of damage variation in unidirectional compression and tension. Confrontations with experimental test results are established.

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Abstract-The calculation of circular sections is not easy given the available reinforcements induces several unknowns in the equilibrium equations. The abacus of Davidovici, based on the principles of BAEL91 and EUROCODE2, assuming a uniform distribution of steel over the entire section, to determine the longitudinal reinforcement of these section bending made for this type of section limited in the case of a compressive axial load.In this study we propose a method for calculating circular sections under any combined loads (N, M), using discrete reinforcement able to take into account both the compressive and tensile axial load. This method is based on the interaction curves of reinforced concrete sections that may generate the number of steel bars necessary for the point representative of the combination load (N, M) is within the strength domain of the section.