Strengthening of RC Columns with NSM Bars and CFRP Jacketing

This paper shows the results of an experimental study on the behavior of rectangular reinforced concrete columns that strengthened in bending with NSM FRP bars and CFRP jacketing under combined compression axial load and cyclic lateral loading. Near surface mounted (NSM) fiber reinforced polymer (FRP) is one of the best retrofitting techniques for reinforced concrete (RC) structures. This technique is based on inserting fiber reinforced polymer bars into slits in the cover of reinforced concrete members. For this purpose, seven rectangular RC columns including one control specimen constructed and tested under constant axial load and lateral cyclic displacement. Experimental parameters include different ratios of NSM FRP bar, maximum lateral load capacity, and failure modes are describes based on the test results. The crack patterns in the specimens are also presented. Also, the study was designed to evaluate the necessity of anchoring the end of NSM FRP bars in the foundation. The test results show that a significant increase in the load carrying capacity, stiffness, and energy dissipation of rectangular RC columns can be achieved by using the NSM technique.