Suspensibility of Steel Fibre Reinforced Concrete Values with External Ribbed Armature

Abstract

In 2013, Lviv National Agrarian University patented reinforced concrete beams containing fibre external reinforcement and steel reinforcement tape with end anchors. Such technical solutions aimed at significantly reducing the cost of construction by reducing the complexity of manufacturing due to the complete replacement frames and ribbon fibre. The task of this work was to determine experimentally the bearing capacity of normal sections of steel-fibre reinforced beams with ribbon valves and compare them with the designed according to normative documents and to develop proposals for a refined calculation methodology. For studies of the bearing capacity of normal sections, 3 beams were manufactured in the size of 1500x150x60 mm. The first beam B-1, reinforced with steel strip valves in the sizes of 1500x60x3 mm with end stops, executed without fibres; The second and third beams (BF-2, BF-3) contained, in addition to the specified reinforcement, fibres in the amount of 1.59 kg and 2.12 kg, which corresponded to the coefficient of fibre reinforcement in volume, ρfv=1.5% i 2% respectively. For disperse reinforcement, an anchor fibre type with curved ends HE 1050 type in diameter of 1 mm and length of 50 mm was taken, because it is a mass produced fibre in Ukraine and abroad. The percentage of fibrous reinforcement in the volume of samples taken = 1.5% and 2%, to obtain a power effect, ensuring a sufficient bearing capacity for both normal and inclined cross-sections. As a binder for the production of concrete C20/25, cement of the mark 400 (activity 42.3 MPa). Experimental samples were made of fine-grained concrete, for the manufacture of which Yasinetskyi sand was used with a grain size unit of no more than 2.5. The composition of the mixture was chosen in such a way that the fibres could not settle down to the bottom of the forms; the cone’s settling did not exceed 4-6 cm. Characteristic issue was that with an increase in the number of fibre reinforcement in the beams there was a large number of cracks. Closer to the supports, they were tilted to the longitudinal axis, indicating a joint effect on the cracking process, both bending moments and transverse forces. It has been experimentally established that the bearing capacity of steel-fibre reinforced composite reinforced beams was 16% and 21% higher than the percent reinforcement of fibres 1.5 and 2, respectively, in comparison with steel concrete. For identical values of bending moments of strain relief, the deformation of the extreme compressed fibres of concrete and the deflection of beams containing fibres are smaller than fibres without beams. The calculation of the deformation method gave a good convergence of theoretical and experimental results. Ukrainian norms for the design of steel-fibre-reinforced concrete structures require the replacement of a power calculation method using rectangular stresses of strain with a deformation method.