Description
Few numerical investigations have been carried out on fiber-reinforced polymer (FRP)-jacketed substandard RC columns with characteristics not normally met in properly designed structural members. Three columns were modeled through finite element method (FEM) by means of ATENA and OpenSees considering their cyclic lateral-load displacement hysteretic responses, where i) the first column (S) represents the typical characteristics of substandard columns violating rules of their construction time (i.e. 1975 Turkish Seismic Design Code) in terms of compressive strength of concrete (𝑓𝑐≈10 MPa) and transverse reinforcement detailing (𝑠=250 mm, where 𝑠 is stirrups spacing), ii) the second column (C) represents the columns of buildings thoroughly complying with the requirements of their construction time (i.e. 1975 Turkish Seismic Design Code) (𝑓𝑐≈19.5 MPa and 𝑠=80 mm), and iii) the third column (RS) is identical to substandard column (S), but retrofitted with a CFRP jacket of 1 ply thickness. High axial load-to-axial capacity ratio (0.75𝑓𝑐𝑏ℎ) together with high shear demand (ratio of shear force corresponding to the moment capacity (𝑉𝑒) to shear strength (𝑉𝑟) of 0.55) were among main features of the substandard column (S). In OpenSees, fiber-discretized sections along the column height are modeled, allowing to account for distributed plasticity. Both the slip of longitudinal bars at the column-foundation interface and buckling of these bars in compression were considered. Furthermore, cyclic stiffness and strength degradations were captured as well. In ATENA, the columns were modeled as a single macro element and discretized by fine meshes capturing both flexure and shear deformations. The results obtained through the numerical modeling were in a good agreement with the experimental ones. The ductility of column C was much enhanced with respect to Column S. Results also showed that the brittle/undesired failure mode of Column S was improved significantly after the seismic retrofit using CFRP jacketing.
