Of recent a large nllmber of existing rei"forced concrete bllildings have reqllired reconstruction, renovation and improvement. This tendency poses a "w"ber of problellls that have to be solved, the main aile being to determine the actual strength condition of the structural components/elements of the bllilding. It includes determ inatioll of the quality of materials used, specificatiol/ orthe types (/I/d description of apparent fa II Its and damages and extent of wear of the bllilding. To undertake this evaluation, non - destructive testing methods are IIsed. In this paper, applications of lion - destructive testing methods to determine the strength state of reinforced concrete colllll1ns with corbels and to establish their structural strength so as to deterl7line the capacity of a mobile crane to be installed is olltlined.