Influence of load level during strengthening of reinforced concrete beams on their reliability

The main purpose of article is to study the influence of load level on the reliability of non-damaged reinforced concrete beams with rectangular cross-section during strengthening by adding stretched steel reinforcement. On the basis of real samples testing of the existing and advanced methods of reliability estimation (depending on the variant of random parameter of the load level at the strengthening moment), adapted to the national norms of reinforced concrete structure design, the recommended value of failure-free probability P(β) – within ranges 0.999624-0.999758 and 0.999606-0.999775 (for two of considered variants, respectively). The comparative analysis of obtained results is conducted depending on the additional steel bar diameter (Ø10 mm, Ø12 mm, Ø14 mm) and load level at the strengthening moment (0.0×M_ult, 0; 0.3×M_ult, 0; 0.5×M_ult, 0; 0.75×M_ult, 0, where M_ult, 0 is bearing capacity of non-strengthened beam). Practical utility of the study results could be associated with the possibility of usage both existing as well as developed methodology to evaluate reliability for design of bended reinforced concrete elements, strengthened with additional stretched steel rebar subjected to load (simulation of the actual element performance during strengthening), especially in the case of proving reliability levels of its design.