Experimental analysis of load capacity in beams with reinforcement of steel fibers
AbstractThe use of steel fibers in the concrete is mainly aimed to increase the post-peak toughness, due to the adhesion of the fibers to the cementitious matrix and to improve brittle behavior of the concrete. However, since there are various types of steel fibers, it can be said that the main difference is the characterization of macrofibers and microfibers that generally serve to soften the macrofissuração and microcracking, respectively. Within this context, this study aims to evaluate the use of microfiber (20kg/m³), macrofibers (20kg/m³) and hybridization (microfibre (10kg/m³) + macrofibers (10kg/m³)) entered into a concrete high strength (fck = 80 MPa) acting as reinforcement on the face pulled large armed beams (12x20x160 cm) high strength concrete, and in addition were examined: the flexural strength in non-armed small beams (10x10x35 cm), the compressive strength and modulus of elasticity on cylindrical specimens (20xØ10 cm). All tests were compared to the reference concrete without addition of high-strength fibers. After the execution of all experimental tests the results were analyzed using an analysis of variance (ANOVA). The results showed that the compressive strength was increased by approximately 8% for all compositions relative to the reference fiber. The modulus of elasticity was observed values similar among all groups. For small beams the main increase was in the toughness, and the macrofibers generated the best performance. Finally, with respect large beams, it can be said that the best advantage was increased load capacity as the moment of cracking and plastic rotation, and the best composition were also isolated macrofibers. In general, it can be concluded that the application of reinforcing steel fiber in the face of large tensioned beams is effective even though not show increases in the ultimate strength, the fibers contributed satisfactorily cracking.