Basic parameters of crack resistance of conventional and damaged reinforced concrete beams strengthened by carbon plastic under the action of a high-level load.

Abstract

The main results of experimental studies of the fracture resistance of conventional and damaged and brought to the limit state according to I group in the previous experiments of reinforced concrete beams reinforced with fiberglass carbon fiber (СFRP) in the lower stretched zone and at the supporting areas. According to the adopted methodology, a full-scale experiment was performed on a four-factor three-level Box-Bank B4 plan. The tests of the prototypes were carried out according to the scheme of a single-track free-beam, alternately loaded from above, then from below by two concentrated forces without changing its (beam) position. During testing of the test specimens-beams for the action of short- term one-time and small-cycle loads, the formation, development and width of crack opening on their surface were monitored. The width of the opening  of normal cracks was determined at the level of the stretched working armature, and the inclined ones - in the middle of the height of the beam in places where it was visually greatest. Due to the adopted methodology, new experimental data were obtained to substantially refine the physical models of the inclined sections of the precast concrete structures by the action of low-cycle reloading of high levels, resulting in the first identified systemic effect on fracture toughness.

Keywords: concrete, reinforcement, carbon fiber fabric (CFRP), reinforced concrete beam, normal and inclined cracks, deformations.