Study On Shear Performance Of Rectangular Section Concrete Beam Reinforced By Ultra-short Ultra-fine Steel Fiber

The study on shear capacity of reinforced concrete components is one of the classicproblems of the basic theory of concrete structures. As the influencing factors of shearfailure are numerous, the factors interacts with each other and the failure forms arecomplex, until now, the shear mechanism of concrete still has not reached a consensus.It until now cannot be established into a complete theory as the flexural bearing capacity.The application of ultra-short ultra-fine steel fiber is boarder and boarder. And the mixof it complicates the shear performance of concrete components reinforced byultra-short ultra-fine steel fiber. The calculation formula of the shear capacity of steelfiber according to the already existing “Design and Construction Procedures of SteelFiber Structure” of our country was gained on the basis of regression analysis of a largenumber of experimental data. However, those experiments did not involve the one usingultra-short ultra-fine steel fiber, moreover, the types of ultra-short ultra-fine steel fiberare various, and so the procedures mentioned cannot reflect the influence of ultra-shortultra-fine steel fiber on shear performance. Consequently, it requires further studies toensure that the shear performance of concrete reinforced by ultra-short ultra-fine steelfiber can be calculated according to the formula from existing regulations, and thereliability of the regulations concerning to shear performance can meet the requirementsof reality.In this paper, a series of preliminary experiments were carried out from which it wasgained that the basic mechanical property parameters of the concrete reinforced byultra-short ultra-fine steel fiber. Then six test beams were designed for shear failure testsunder concentrated loads. Two of the beams are made of ordinary concrete for the usageof comparison. And the rest four beams are two beams mixing with ultra-short ultra-finesteel fiber and two beams mixing with ordinary steel fiber. Through preliminarycalculation, the reinforcement ratio, cross-sectional dimensions and shear-span ratio aredetermined which leads to the shear failure of the beams. During the experiments, it ismeasured that information such as diagonal cracking load, shear failure load, crackforms and its transformation laws and corresponding longitudinal reinforcement andstirrup strain. The main control parameters of the beams are the reinforcement ratio andthe content of ultra-short ultra-fine steel fiber. According to the analysis of theexperimental data, the influence law of different reinforcement ratio and different content of ultra-short ultra-fine steel fiber are obtained on the shear performance of thebeams. Then on the basis of the experiments, the finite element method was applied.Basing on reasonable simulation which is similar to the actual stress situation of thebeams, more intuitive description, additional support and valid data are provided for theanalysis of the problem. At last, on the basis of the data gained by modeling andexperiments, combining with the existing regulations, the empirical formula of shearperformance of the rectangular section beam reinforced by ultra-short ultra-fine steelfiber concerning to the experiments is proposed to provide a reference.