Reinforced Steel Fiber Reinforced Concrete Beams By Experimental Study On Properties

Steel fiber reinforced concrete has been widely used in every fields of civil engineering since the Design and Construction Specification of Steel Fiber Reinforced Concrete Structures (CECS38:92) issued in 1992. But values of calculating parameters specified in this specification are only suited to strength degree of fiber reinforced concrete from CF20 to CF40, it is also could not determine the enhancing coefficients of steel fiber to the shear resistance of reinforced concrete members by the simple test method of material because these coefficients are not combined with the strength of steel fiber reinforced. Therefore, 16 steel fiber reinforced high-strength concrete beams are tested to revise the current specification. Based on the experimental results, the following conclusions have been drawn:1. Inclusion of steel fibers in the concrete mix improves the shear capacity of RC beams, because the presence of the steel fibers increases the dowel action of steel bar and the friction of aggregates.2. Addition of steel fibers in the concrete mix delays the appearance of inclined sectional crack and increases the cracking strength of inclined section. And after the appearance of inclined sectional crack, steel fibers limited the development of the crack and made crack shape more thin and intensive.3. The effects of the shear-span to depth ratio on the shear capacity and cracking strength of steel fiber reinforced concrete beams are also studied in this paper. The test data and research data found in the literature indicated the shear capacity and cracking strength of inclined section increase obviously with a decrease in shear-span to depth ratio.4. The data of this experiment show us that the advantage of the stirrups to the shear cracking strength of steel fiber reinforced concrete beams is not obviously, because the radius of stirrups is small and its surface is smooth.5. The influence of steel fiber on cracked shape of shear critical beams is discussed. Then, the relationships between compressive strain of concrete in shear & compress zone and load-mid span deflection curveswith the main factors such as steel fiber, stirrups and shear span ratio are investigated. At last, shear ductility are analyzed.6. Combined with the test data and other researches, the effects of steel fibers, stirrups and shear-span to depth ratio on the cracking strength are analyzed and an equation is proposed to predict cracking strength of inclined section.7. According to test data and failure mechanism, the calculating model was proposed to predict shear capacity of inclined section of fiber reinforce high-strength concrete beams.