Investigation on the structural behaviour of rc rectangular columns using steel, CFRP and geogrid as continious spiral reinforcement

The columns, which are members of the structural system, provide vertical stability of the structure against lateral effects in the whole system, especially due to earthquake and wind. In addition, those members are subjected to simultaneous effects such as axial force, bending moment, torsional moment, and shear force. Therefore, required attention should be provided in the design and production of the columns. In this study, behavior of reinforced concrete (RC) columns under axial and lateral loads was investigated. It is expected to have a ductile behavior as well as a high level of strength from the columns under those loadings. Accordingly, contribution of transverse reinforcements is of great importance. CFRP sheets and geogrid material can be applied as transverse reinforcement in RC columns in a more feasible manner than steel bars. The effects of using these materials as stirrups in traditional closed-form and spiral-form were experimentally investigated within the research. In this context, structural behaviors of full-scaled RC columns under cyclic lateral loading and constant axial loading, designed and produced in accordance with design codes, were compared. As expected from the usage of transverse reinforcements, load-bearing capacities against lateral loads of the test specimens with spiral reinforcements, were increased. Depending on the disadvantages of mechanical properties of geogrid material, when it is used as closed-stirrup, structural performance of the columns decreased with respect to usage of steel. Application of CFRP sheets as transverse reinforcement in both closed-form and spiral-form, provided higher moment capacity compared to usage of steel.