Seismic Behavior of Repaired and Externally FRP-Jacketed Short Columns Built with Extremely Low-Strength Concrete

Short columns with deficiencies of low-strength concrete and large spacing of transverse reinforcement are quite common in construction practice in many developing countries in seismically active regions. Therefore, it is important to retrofit this type of column to avoid negative consequences in the case of severe damage. External fiber–reinforced polymer (FRP) jacketing is one of the most practical methods to retrofit reinforced concrete (RC) frame members against shear actions. However, knowledge of the seismic behavior of FRP-retrofitted RC short columns is still limited. Thus, the aim of this study was to investigate the seismic response of FRP-retrofitted low-strength RC short columns with and without predamage through the testing of 11 short column specimens representing old and deficient RC buildings. Accordingly, the results of a research program on the seismic behavior of such columns and on their repair and FRP retrofitting, covering experimental and analytical phases, are presented. In the experimental phase, test results obtained for short columns, FRP-retrofitted short columns, and repaired and retrofitted short columns are documented. Test results provide important knowledge about the effects of extremely low-strength concrete, and of different levels of predamage on the behavior of FRP-retrofitted substandard short columns. In the analytical phase, the performance of relevant design documents in predicting the shear strength of such columns retrofitted with FRP jacketing was tested through the comparison of predicted and experimental results.