Influencia da largura do corpo-de-prova na medida da tenacidade do concreto reforçado com fibras de aço




Toughness indices for steel fiber reinforced concrete (SFRC) may be affected by several factors, depending on the methods adopted and procedures for flexural testing under controlled deformation. These factors include, among others: test configuration; loading configuration; rate and control of loading; type of deflection-measuring equipment; type of test machine; temperature at testing; specimen size and geometry. This study has the objective of analyzing the influence of specimen width on the toughness measurement of SFRC, focusing on the most used toughness indices nowadays. Laboratory tests were performed for the determination of the flexural toughness in prismatic steel fiber reinforced concrete specimens, with width of 150, 300 and 450 mm. For each width, specimens with fiber volume contents of 20, 30 and 40 kg/ m3 were cast and tested, aiming at comparative results. These experimental results were used to compute toughness indices according to the methods specified by JSCE- SF4 (Japan Society of Civil Engineers) and EFNARC (European Federation of Producers and Applicators of Specialist Products for Structures). Mathematical models were fitted to each group of resulting toughness indices to correlate the toughness index to the fiber volume content and to the width of the specimen. The resulting mathematical models lead to the conclusion that the fiber volume content affects significantly the flexural toughness of the concrete reinforced with steel fibers. Considering the method JSCE-SF4, the increase of the fiber volume content produces not only an increase of the flexural toughness, but also an increase of the equivalent flexural resistance, and of the ductility coefficient. For the method EFNARC, the same is valid for the bearing capacity, and for the residual stress. The same tendency was observed for the three specimens width investigated. With respect to the influence of the specimen width on the measurement the SFRC flexural toughness, statistical analysis have showed that the shape of the P-õ curve is strongly dependent on the specimen width. As most toughness indices have their calculation based on the P-õ curve, flexural toughness and both equivalent flexural resistance and ductility coefficient are affected by the specimen width (JSCE-SF4 method). On the other hand, in the EFNARC method, the toughness measurement through the residual stress was shown more independent from the specimen width


fibras de metal flexão (engenharia civil)

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