Experimental and numerical investigation for compression response of CFRP strengthened shape modified wall-like RC column S.H. Alsayed, T.H. Almusallam, S.M. Ibrahim, N.M. Al-Hazmi, Y.A. Al-Salloum, H. Abbas ⇑ Specialty Units for Safety and Preservation of Structures, Department of Civil Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia highlights  Studied axial compression behavior of wall-like RC column strengthened with CFRP.  Rectangular section of column was transformed to elliptical shape using mortar.  CFRP confinement increases concrete axial strength and strain capacity.  Strengthened column showed post-peak softening behavior. article info Article history: Received 28 October 2013 Received in revised form 23 March 2014 Accepted 2 April 2014 Keywords: Column Shape modification FRP Concrete Finite element analysis Strengthening Wall-like abstract Introduction: The compression behavior of Carbon Fiber Reinforced Polymer (CFRP) strengthened wall- like rectangular reinforced concrete (RC) column after shape modification is presented. The research includes laboratory testing of rectangular RC columns externally confined by CFRP laminates after trans- forming the cross section into elliptical one using cement mortar. The finite element analysis was carried out to predict the load–displacement behavior of the test specimens. Results: Parametric studies pertaining to the effects of CFRP strengthening of wall-like columns on failure mode, strength, ductility, yielding of longitudinal and transverse reinforcement, confinement and dilata- tion are discussed. For the strengthened column, the stress–strain curve showed post-peak softening behavior. The CFRP confinement increases concrete axial compressive strength, but it is more effective in enhancing concrete strain capacity. The actual failure of the strengthened column was due to crushing of concrete and buckling of longitudinal rebars. Conclusions: It is demonstrated that for cases where ductility and slenderness of the column are major issues, CFRP strengthening of columns after transforming the column cross section to elliptical one may be one of the cheapest mitigation solution. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The structural members such as beams and columns are frequently required to be strengthened to eliminate structural problems or distress which results from unusual loading or expo- sure conditions, aging, inadequate design, new codal provisions or poor construction practices. Upgradation of such structural members with fiber reinforced polymers (FRP) sheets is commonly used because of their ease of application, low weight to strength ratio and high corrosion resistance. Another advantage of using FRP as strengthening technique is that there is only a slight change in the existing structure’s inertial mass and profile. FRP confine- ment is accomplished by placing the fibers mainly transverse to the longitudinal axis of the member providing passive confine- ment, which is activated once the concrete core starts dilating as a result of Poisson’s effect and internal cracking. However, for thin and slender structural members under compressive loads, the longitudinal FRP also helps in resisting global buckling. The effec- tiveness of the FRP confinement in delaying and limiting unstable crack propagation, thereby enhancing concrete axial deformation and strength, primarily depends on the stiffness of the FRP jacket [1–4]. It is known that because of the geometrical configuration, rehabilitation of circular columns using FRP wraps results in an effective upgradation of strength and deformability. Extensive experimental investigations were carried out in the past which established the effectiveness of FRP confinement on circular columns (e.g. [5–15]). In these cases, the wraps provide circumfer- entially uniform confining pressure to the radial expansion of the http://dx.doi.org/10.1016/j.conbuildmat.2014.04.047 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +966 114670638; fax: +966 114673600. E-mail address: abbas_husain@hotmail.com (H. Abbas). Construction and Building Materials 63 (2014) 72–80 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat