The paper deals with the results of multi-method test studies of the bearing capacity, stress-strain behaviour and crack resistance of the 2000х200х100 mm reinforced concrete beams and basalt fibre reinforced concrete beams subjected to high-level static and low-cycle loads. Specifically, the test-statistical curves illustrating strengths of the inclined cross-sections (collapsing transverse force). There are examined moments and the developed transverse forces for normal and inclined cracks, the deflection and crack widths subjected to service and collapsing loads. The projection lengths of the dangerous inclined cracks on the longitudinal axis and the average distances between normal cracks along the element lengths versus the design factors of the concrete beams similarly reinforced with steel and basalt-plastic were compared. Comparative analysis was made to check the impact of the main design factors on the indicated load-bearing capacity parameters of the reinforced concrete beams and basalt fibre reinforced concrete beams manufactured and tested in accordance with the experimental design theory and D-optimum plan of Box B3.