Experimental Study of Crack Resistance and Shear Strength of Single-Span Reinforced Concrete Beams Under a Concentrated Load at a/d = 1

Abstract

At a stage following the crack development, a reinforced concrete beam has a complex structure that does not correspond to such simple systems as the truss, arch or strutted frame. Therefore, to establish a possible design model for calculating the shear strength, it is necessary to know not only the failure pattern, but also the order of crack nucleation and propagation in the loaded structures. The pattern of nucleation and propagation of diagonal cracks differs significantly from that of vertical cracks, which are the reason for the stretching stress or bending moment. Diagonal cracks can be far more dangerous, as the time interval between the crack nucleation and failure is considerably shorter than for pure bending. The paper discusses the experimental study of diagonal cross-sections of single-span reinforced concrete beams under a concentrated load for a/d = 1. The tested beams had identical characteristics and differed only in the type of transverse reinforcement. The analysis of the experimental data revealed the specifics of nucleation and propagation of diagonal cracks in the zone of impact of the shear force and bending moment. The dynamics of propagation and width of diagonal cracks opening was recorded depending on the load. The effect of different types of transverse reinforcement on the bearing capacity of the beams was established.

Improving the crack resistance of inclined cross-sections of reinforced concrete containment shells in areas of emergency loads of pushing

“…Concrete cubes installed around the perimeter of the sample modeled the resistance distributed along the perimeter of the circle at a distance of ≈135 mm from the limit of load application. The fracture angle γ was close to 40° at the accepted sample thickness d, which was 160 mm (3-1... [3][4][5][6][7][8][9][10][11][12] and up to 34° at a thickness of 200 mm (3-13... in the samples of the second series. The partial effect of the clip was achieved by reinforcement of Ø12 class A240 at the ends of working rods of the nets in the form of a ring.…”

“…In these areas, the maximum pitch of vertical knitted clamps should not exceed 150 mm, and the pitch of nets or individual rods in the middle zone of the node should not exceed 100 mm. The strength of inclined sections on the cut using multi-row horizontal reinforcement in beams and thick slabs is well studied [8]. But the studies are limited to cut spans at fracture angles of 45-63.4°, which corresponds to static loads, but not dynamic.…”

“…When calculating the static (k d =1) component of F v and F n (Table 6), the estimation area A, according to (5), was assumed equal to 0.253 m 2 (samples 3-1... [3][4][5][6][7][8][9][10][11][12] and 0.2918 m 2 (samples 3-13...3-24). In addition, the tensile strength of concrete f ctm , obtained experimentally by testing cubes for splitting with rods with a diameter of 12 and 14 mm, was used.…”

STUDY OF THE LOAD-BEARING CAPACITY OF STRUCTURES of LONG-TERM OPERATION OF THE FORMER "MODULE" PLANT IN UZHGOROD

“…Works [8,9] discuss methods for repairing reinforced concrete structures with long-term damage to ensure crack resistance, strengthening vertical and inclined sections using steel reinforcement (clamps, bends), and in work [10] using fiber, non-metallic fiber and carbon tapes etc. Some of these methods are effective when there is access along the entire height of the bending elements to inclined sections, and when access is only to the top and bottom edges, they are used to strengthen normal areas.…”