ABSTRACT Five square columns with two shear span-to-depth ratios of 1.5 and 2.5 were constructed to model half-scale shear-deficient columns and tested under constant axial compression and reversed cyclic lateral load, simultaneously. After being tested, two of the columns with different shear span-to-depth ratios were subjected to a certain level of damage in terms of crack pattern and also drop in the lateral capacity. Then, these earthquake-damaged columns were retrofitted by pre-tensioned carbon or aramid FRP belts, and once more, were tested under cyclic lateral loading and constant axial compression. As the confining devices, i.e. FRP belts, were pre-tensioned before applying the lateral load to the columns, both active and passive confinements were utilized. As an instant result of pretensioning, the initial cracks of the damaged column were closed. It should be noted that this retrofitting procedure is quick as it is carried out without any repair measures such as removal of damaged concrete or crack injection and so on. Moreover, the prestressing technique is an innovative method and can be applied manually using a simple wrench. According to test results, the lateral capacity of the original columns dropped suddenly, showing a brittle shear failure. When the damaged columns were retrofitted by pre-tensioned FRP belts, the lateral strength could be restored and the drop in shear capacity could be prevented up to large drifts, indicating a better seismic performance
