Seismic strengthening of low strength concrete columns by external confinement using prefabricated SFRCC panels

Inadequate ductility and low quality concrete are among the most common deficiencies of relatively older existing reinforced concrete structures in terms of seismic safety. Although there are various methods to overcome these problems, many times these methods are not feasible due to their high cost or disturbance to occupants. In this study, a retrofit technique in terms of external confinement of concrete members by using prefabricated panels of steel fiber reinforced cementitious composites (SFRCC) is investigated. For this purpose two different experimental programs are carried out in parallel fashion. In the first group tests, concrete members with rectangular cross-sections were externally confined by using prefabricated SFRCC panels and tested under monotonic axial loads. In the second group tests, retrofitted reinforced concrete column specimens, representing the column parts between the mid-heights of succeeding stories and the beam-column connection were tested under constant axial load and reversed cyclic lateral loads. For both test programs, the concrete compressive strength of original specimens was around 10MPa for representing the concrete quality of existing structures, particularly in developing countries. The compressive and tensile strengths of the prefabricated SFRCC panels were around 100 and 14MPa, respectively. Test results showed that external confinement with prefabricated panels provided significant enhancement in ductility, aswell as a less pronounced strength enhancement. The investigated technique seems to be a promising method due to ease in application, relatively less hindrance to the building occupants, high efficiency in the case of non-circular members, better quality control due to prefabrication and relatively less cost with respect to other alternatives.