Experimental investigation of the behavior of the concrete columns strengthened by cfrp strips under the axial load effect

In this study, it was aimed to increase the axial load capacities of square cross-section reinforced concrete columns by using differently shaped details with carbon fiber textile composite (CFRP) strips and an experimental study was carried out. The main purpose of the study is to develop strengthening details that will not adversely affect properties such as displacement ductility capacities and energy consumption capacities to avoid adverse effects on earthquake performances. Improved strengthening details have been applied to a square cross section reinforced concrete column with low axial load capacity, low compressive strength of concrete and inadequate amount of stirrups, which is not designed according to regulations. It is aimed to increase the axial load carrying capacity of column by wrapping column with carbon fiber textile composite (CFRP) strips. The main variables examined in the study are the CFRP strip width, the spacing of CFRP strips, the use of anchorage in the overlap zone in CFRP strips, and the placement of CFRP strips horizontally or vertically on the column axis. In the experimental study, eleven reinforced concrete column specimens with dimensions of 150x150x500 mm were produced, one specimen being nonstrengthened reference specimen. These specimens were exposed to monotonic loading until collapse. Axial load-displacement graphs of the test elements are drawn. The ultimate axial load capacity, initial stiffness, displacement ductility ratios and energy dissipation capacities of the test specimens were calculated. It was investigated how the variables in the experiments affected the behavior of the columns. The performances of the details developed for strengthening have been examined and interpreted.