STATISTICAL EVALUATION OF MECHANICAL CHARACTERISTICS COLD-FORMED CLASS B500 REINFORCEMENT

Abstract

The paper presents the results of astatistical evaluation of the mechanical characte-ristics of cold-deformed reinforcement of class B500.The statistical evaluation was performed on thebasis of the results of tensile tests of 485 samples ofclass B500 reinforcement, made of St3ps steel wirerod, with diameters of 5 mm (160 samples), with adiameter of 6 mm (133 samples), with a diameter of8 mm (142 samples) and 10 mm in diameter (50samples), selected from skeins of industrial production. During the tests, the main mechanical characteristics of B500 class reinforcement were determined - yield strength (σТ), ultimate resistance (σВ),ratio of ultimate resistance to yield strength (σВ/σТ),total relative elongation at maximum load (δmax),state diagrams were constructed and the modulus ofelasticity of reinforcement (Es) was determined.Statistical evaluation of the mechanical characteristics of the reinforcement was performed for each ofthe investigated parameters (σТ, σВ/σТ, δmax), for eachof the diameters and for the whole sample and included the determination of the minimum, maximum and average values, root mean square deviation, coefficient of variation, construction of histograms of distribution with a comparison of themwith the normal law of distribution, reliability andcomparison with the corresponding standardizedvalues, the reliability coefficient for the material γsfor cold-deformed reinforcement B500 when calculating structures according to the first group of limitstates.As a result of the tests, it was found that the mechanical indicators characteristics for different diameters have close values, and their distribution isclose to normal. In general, for the sample, the yieldstrength varies within the range of 500.00...800.00MPa, the ultimate resistance - within the range of550.00...830.00 MPa, the ratio of the ultimate resistance to the yield strength - within the range -1.031...1.309, the full relative elongation at maximum load - within 2.286...4.857.At the same time, the coefficient of variation ofthe yield strength was 0.088, the ultimate resistancewas 0.079, the ratio of the ultimate resistance to theyield strength was 0.037, the total relative elongation at maximum load was 0.162 and was close tothe corresponding values for hot-rolled and thermomechanically strengthened reinforcement. The yieldstrength was 0.964, the ratio of temporary resistanceto yield strength was 0.939, total relative elongationat maximum load was 0.946, which corresponds tothe normalized values for these indicators, whichare 0.95, 090, and 0.90, respectively. The reliabilitycoefficient for the material as a whole for the samplewas 1.143, which is less than that established in regulatory documents for the design of reinforced concrete structures