Cyclic behavior of full-scale RC columns externally jacketed with FRP sheets after fire exposure

The impact of sequential occurrence of fires and earthquakes on reinforced concrete members particularly columns is not well understood and may be critical in the event of aftershocks and/or future earthquakes. This paper presents the results of an experimental study with a primary objective of assessment of the effectiveness of carbon fiber reinforced polymer (CFRP) jacketing in improving seismic performance of fire-damaged flexure critical full-scale reinforced concrete (RC) columns complying with current major design guidelines (e.g. ACI-318-14). Outcome of the test results on a total of four RC columns are discussed within the study. One of the columns was an unheated reference specimen while the other three were heated 90 minutes following ISO-834 standard fire curve in a fire furnace. One of the heated columns was kept unjacketed whereas the other two were externally jacketed by 2 layers of continuous circumferential CFRP sheets i) without removing fire-damaged concrete cover after fire exposure, ii) after removing concrete cover over the hinging zone and re-forming this cover with a repair mortar prior to jacketing after fire exposure. The post-fire seismic tests were carried out under constant axial load and reversed cyclic lateral displacements. The structural behavior of the columns is discussed through hysteretic and envelope curves. The test results show that CFRP jacketing after fire exposure improved lateral load capacity and deformation characteristics of RC columns with respect to fire-damaged column significantly whereas intervention to concrete cover after fire exposure and prior to FRP jacketing did not remarkably influence the behavior. On the other hand, when compared to unheated reference column, FRP jacketing could almost reinstate the lateral load capacity to the original and enhanced the displacement ductility remarkably.