Experimental investigation of the effectiveness of strengthening methods in reinforced concrete flat slabs with multiple openings under punching load

Abstract

In this study, an experimental investigation was carried out to strengthen reinforced concrete flat slabs with multiple openings against punching load via three different strengthening methods. The methods applied in this investigation are (a) shear stud method, (b) textile reinforced mortar (TRM) method, and (c) carbon fiberreinforced polymer (CFRP) method. Thirthy-eight specimens with dimensions of 2000 mm x 2000 mm x 120 mm were produced, and the study was conducted in four series. The first series, consisting of ten specimens, was selected as the reference series in which strengthening operation was not applied; one specimen was produced as solid (no opening) and the rest with openings. The second series was identical to the first series and strengthened with the shear stud method.The third and fourth series were formed from nine specimens with openings, and each sequence was strengthened by textile-reinforced mortar and carbon fiber-reinforced polymer methods, respectively.The variables planned to be examined in this study were chosen as the presence, the location, the dimension of the openings, and the strengthening type. Load-displacement graphs were obtained for each specimen subjected to concentric monotonic static loading, and by employing these graphs; the essential performance indexes such as ultimate load-carrying capacity, initial stiffness, and energy dissipation capacity of the specimens were calculated. It has been revealed that the size and the position of the openings are effective on the performance indexes of the specimens. Significants increases in the ultimate load-carrying capacity, initial stiffness and energy dissipation capacities of the strengthened specimens are among the main findings of this study. Furthermore, the effectiveness of the strengthening methods was discussed by comparing the performance indexes at the end of the study.