STATISTICAL EVALUATION OF MECHANICAL CHARACTERISTICS REINFORCEMENT OF CLASS A500С IN COILS

Abstract

The paper presents the results of astatistical evaluation of the mechanical characteristics of reinforcement of class A500S in coils.The statistical evaluation was performed based on the results of tensile tests on 144 samples of 8 mm diameter rebar of A5000S class made of St3ps steel. The samples were taken from 8 coils of different batches of industrial production, 6 samples fromthe beginning, middle and end of each coil. During the tests, the main mechanical characteristics of A500C reinforcement were determined - yield strength (σТ), ultimate strength (σВ), ratio of ultimate strength to yield strength (σВ/σТ), relative elongation after rupture (δ5), state diagrams were drawn and the elastic modulus of the rebar (Es) was determined. The statistical evaluation was performed for each of the studied parameters (σТ, σВ,σВ/σТ, δ5) first separately for each skein for samples taken from the beginning, middle and end, then for all samples taken from the beginning, middle and end of all skeins, respectively, and finally forthe entire sample of 144 samples.According to the test data of samples from 8 coils, the yield strength of A500C reinforcement varied in the range of 532.80...631.10 MPa, the temporary resistance - 697.30...762.70 MPa, the relative elongation at break - 18.75...30.00 %, the ratioof temporary resistance to yield strength -1.185...1.344.No stable patterns of change in the mechanical characteristics of the reinforcement along the length of the coils were found. The difference between the average values of yield strength, temporary resistance, relative elongation, and the ratio of temporary resistance to yield strength along the length of the coils did not exceed 2 %.The values of the coefficients of variation and the range of the values of the corresponding mechanical characteristics of the samples taken from the beginning, middle and end of the coils were also close to each other.The yield strength of A500C rebar with a diameter of 8 mm in coils in this sample of samples was 0.9999, with a normalised value of 0.95. The coefficient of variation was 0.0328.For the established security of the calculated reinforcement resistance at the level of 0.998, the reliability factor for A500C class rebar with a diameter of 8 mm in coils was 1.109, which is less thanthe value of 1.15 accepted in the current regulatory documents.