Experimental researches of the work of steel rebar in the cross-sections of continuous combined-reinforced concrete beams

Abstract

Perspective direction of concrete structures improvement are increasing their strength, hardness and shear strength by using statically indeterminate structures. Special place is occupied by statically indeterminate (continuous) reinforced concrete beams, as they most efficiently used components materials - concrete and reinforcement. The dispersed-reinforced materials, including steel fibrous concrete are the one of most promising structural materials that can increase the compressive strength of concrete materials and structures, tensile strength, shear strength, get effective structures which would respond to higher operational requirements. The article presents the results of experimental studies of the work of steel rebar in cross sections of two-span reinforced concrete beams in which classical rebar frames and dispersed reinforcement of concrete with steel fibers are combined.

Experiments were conducted with 300 cm long two-span beams which were made from heavy concrete The size of the cross section was 10x16 cm. The length of spans was 140cm. The additional, dispersed reinforcement of the test specimens was performed by using steel fibers, in a such way, that the specimens had different filling by the fibers volume of the beam, but with the same relative percentage of reinforcement, equal to µ=1%. Thus, the beam 3B-1 was reinforced with fiber throughout its volume, 3B-2 – in stretched zones, 3B-3 –to the height of the two minimum concrete cover zones.

During the testing in special flexural testing frame, was determined deflections, reinforcement and concrete strains, crack width. The load was accepted as fracture, when the strain of reinforcement or concrete reached the limit values. In the course of the research, the new experimental data were obtained, on the basis of which it can be concluded, that the use of additional disperse reinforcement of steel fibers of the stretched zones of continuous reinforced concrete beams, allows to decrease the reinforcement strains, enhance the strength and redistribution off the efforts in spans.