Rapid repair of a severely damaged RC column having fractured bars using externally bonded CFRP Ruili He a , Stephen Grelle b , Lesley H. Sneed a,⇑ , Abdeldjelil Belarbi c a Department of Civil, Architectural & Environmental Engineering, Missouri University of Science and Technology, Rolla, MO 65409, United States b Wiss, Janney, Elstner Associates, Inc., Irving, TX 75038, United States c Department of Civil & Environmental Engineering, University of Houston, Houston, TX 77204-4003, United States article info Article history: Available online 27 February 2013 Keywords: Anchorage Bridge column Carbon fiber reinforced polymer (CFRP) Fractured bars Reinforced concrete (RC) Rapid repair abstract Research on rapid repair of reinforced concrete (RC) columns has been limited to columns with slight or moderate damage. Moreover, few studies have been conducted on repair of severely damaged columns, particularly with buckled or fractured reinforcing bars. In those studies, however, the techniques used involve considerable time and effort and are not considered ‘‘rapid’’. The goal of this study was to develop an effective technique to rapidly repair severely damaged RC columns for temporary service use with externally bonded carbon fiber reinforced polymer (CFRP). This paper describes the repair and retest of three half-scale severely damaged square RC bridge columns within 4 or 5 days. Damage to each column included buckled longitudinal bars, and one column had fractured bars near the column base. The repairs were designed to restore the column strength using longitudinal and transverse CFRP. A novel anchorage system was designed to anchor the longitudinal CFRP to the column footing. This study illustrates the effectiveness and limitations of this repair technique. The technique was found to be successful in restor- ing the strength of the columns without fractured bars, but only partially successful for the column with fractured bars located near the base because of CFRP anchorage limitations. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Based on current seismic design criteria, reinforced concrete (RC) bridge columns are designed to undergo concrete cracking, concrete cover spalling, and yielding of reinforcing steel and to provide a significant rotation capacity at plastic hinges without collapse. Damage to bridge structures during an earthquake can have devastating social and economic consequences, particularly for those that are located along key routes that are critical for emergency response and other essential functions. Such bridges are defined as ‘‘important’’ by ATC-18 [1], which stipulates that damage from an earthquake should be repairable within 3 days. Thus rapid and effective repair methods for varying levels of dam- age are needed to enable quick reopening of these bridges to min- imize the impact on the community of affected areas. For columns with slight or moderate damage, extensive research has been con- ducted in which concrete, steel, or fiber reinforced polymer (FRP) jacketing was used to restore the strength and ductility of the col- umn [2–5]. Few studies, however, have focused on the repair of se- verely damaged ductile RC bridge columns, especially those with buckled or fractured longitudinal reinforcing bars [6–8]. To com- pensate for the loss of strength due to fractured bars, most tradi- tional repair methods have focused on the replacement or addition of internal steel reinforcement [6,7] Although these tech- niques have been shown to be effective in restoring the strength and ductility of severely damaged RC columns, they generally re- quire considerable time to implement, making them difficult to accomplish as part of an emergency repair that can be achieved in a short timeframe. In a study by Saiidi and Cheng [8], glass and carbon FRP sheets with fibers in the axial direction of the col- umn were used to compensate for the flexural strength loss due to the ruptured bars. FRP jacketing has been used extensively to retrofit substandard RC columns that were not adequately detailed to resist seismic loads due to its high strength- and stiffness-to-weight ratios and ease of installation compared with other materials. Because instal- lation and handling time is a critical factor in a rapid repair, FRP is a potential option in rapidly repairing severely damaged columns, although compensating for loss of strength due to fractured or buckled bars can be challenging. In such case, FRP with fibers ori- ented in both the column transverse (jacketing) and longitudinal directions might be considered. Depending on the damage loca- tion, an appropriate anchorage system may be required to anchor the longitudinal FRP to the column or adjacent member when there is not enough bond length to develop its strength. In general, FRP anchorage systems are used to allow the anchored FRP to reach 0263-8223/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compstruct.2013.02.012 ⇑ Corresponding author. Tel.: +1 115733414553. E-mail addresses: rhk82@mst.edu (R. He), sgrelle@wje.com (S. Grelle), sneedlh@mst.edu (L.H. Sneed), abelarbi@central.uh.edu (A. Belarbi). Composite Structures 101 (2013) 225–242 Contents lists available at SciVerse ScienceDirect Composite Structures journal homepage: www.elsevier.com/locate/compstruct