LOAD-BEARING CAPACITY OF DAMAGED REINFORCED CONCRETE SPAN STRUCTURES STRENGTHENED WITH PRESTRESSED METAL CASINGS

This article deals with the results of system experimental research of the loadbearing capacity, stress-strain behaviour and crack resistance of damaged 2,000x200x100 mm reinforced concrete beams with prestressed external metal casings that have been subjected to high-level static and low-cycle alternate loading. Specifically, the teststatistical curves illustrates strengths of the inclined cross-sections (collapsing transverse force), sagging deflections, widths of the normal and inclined cracks before collapse of the beams, 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 and external factors. Comparative analysis was made to check the impact of the main design and external factors on the indicated load-bearing capacity parameters of the common reinforced concrete beams subjected to a single-time stepwise increasing (series 1) and high-level low-cycle alternate loading (series 2) as well as to the strengthened with metal casings beam elements that have been damaged through normal and cross inclined cracks in the course of previous tests (series 3) subjected to a repeated action of similar low-cycle alternate loading. All tested beam samples were manufactured and tested in accordance with the experimental design theory and D-optimum plan of Box B4.