EXPERIMENTAL INVESTIGATION OF DEFLECTED MODE OF THE RIENFORCED CONCRETE BEAMS WITH ORGANIZED CRACKS UNDER LONG-TERM LOADING

Abstract

Introduction. Evaluation of the influence level of the pre-organized cracks in tensile zone of the reinforced concrete beams on their crack resistance, deformability under long-term loading is investigated in the article.Materials and methods. Concrete for specimen was produced in laboratory and factory on portland cement of the 500-grade at W/C=0,71; concrete composition 1:1,9:4 (by weight); strength of cube at 28th days – 13,85 MPa; strength of prism with dimensions 10/10*40 cm – 11,48 MPa; span calculation – 78 cm; steel rebar grade – A400 with diameter of 10 mm. Organized crack was formed by installing plate with thickness of 0,5 mm and height of 30 mm on the rebar in the zone of maximum moments.Results. The experiments confirmed the hypothesis about the beams rigidity with pre-organized cracks in comparison with stochastic cracks under the influence of long-term loading. As a result, the beams with pre-organized cracks provide the smaller deflection after long-term period than the beams without organized cracks. Thus, the proposed method of the deflections calculation of the reinforced concrete beams with pre-organized cracks under the long-term loading helps to reduce deflection to 33%.Discussion and conclusion. The findings of this study suggest that the presence of pre-organized cracks reduces the beams deflections in comparison with the specimens of section, and such method actually regulates the stress-strain state of reinforced concrete structures and leads to the smooth deformation at all stages under the influence of long-term loading.

Keywords

• cracking
• stiffness
• deformation
• deflection
• bending element
• energy theory
• preorganized cracks
• long-term loading
• reinforced concrete beam
• creep