Available online at www.CivileJournal.org Civil Engineering Journal (E-ISSN: 2476-3055; ISSN: 2676-6957) Vol. 8, No. 04, April, 2022 765 Numerical Investigation of HSC Columns Retrofitted by CFRP Materials under Combined Load Mohammed El Youbi 1* , Taoufik Tbatou 2 , Imad Kadiri 1 , Saïf Ed-Dîn Fertahi 3 1 Laboratoire d’Etude des Matériaux Avancés et Applications, EST de Meknes, Université Moulay Ismail (UMI), Meknès, Morocco. 2 Ecole Nationale des Sciences Appliquées (ENSA) – E2MGC, University IBN ZOHR, Morocco. 3 Energy Research Center, Physics Department, Faculty of Science, Mohammed V University in Rabat, Rabat 1014, Morocco. Received 02 January 2022; Revised 25 March 2022; Accepted 28 Marh 2022; Published 01 April 2022 Abstract Repairing and retrofitting old civil engineering structures based on reinforced concrete represents a challenge for civil engineering societies all over the world. Environmental impacts such as corrosion and natural disasters like earthquakes can considerably weaken those structures. Reinforced concrete confinement technique using carbon fiber-reinforced polymers (CFRP) is considered as an innovative solution to strengthen the old and damaged structures. In this paper, a numerical simulation was carried out to evaluate the impact of the CFRP jacket as a confining composite material on the compressive strength and the ultimate strain of confined reinforced concrete. A FE model was developed, validated by comparing its results with the available experimental measurements, and finally assessed by performing a parametric study. Indeed, the parametric investigations had as their purpose the evaluation of the level of confinement (different number of plies), namely without plies, one plie, and three plies configuration, that were subjected to different eccentric loading modes e=0, e=25 and e=50 mm, in order to assess the interaction between the combined load that can be represented by compressive and flexural effect. The numerical results were, in fact, in good agreement with the experimental data. In addition, CFRP wrapping had a significant effect on the maximum load of eccentrically loaded columns compared to concentrically loaded columns by increasing the compressive strength with a value of 15% gain compared to the unconfined column. Keywords: Composite Materials; Civil Engineering; Structures; Reinforced Concrete; FEA. 1. Introduction In civil engineering, several high-strength concrete HSC structures were built according to old design codes before the implementation of the new seismic design guidelines [1-3]. These structures contain non-ductile reinforced concrete columns, which can suffer extensive damage when subjected to an earthquake. The failure of these columns is mainly due to the lack of shear resistance ability and insufficient ductility provided by a small amount of transverse steel. The ductility of a reinforced concrete column plays a very important role in failure prevention. This is why many research works in the last two decades try to improve the ductility of reinforced concrete columns and therefore the safety of the structures [4-7]. One of the effective ways to improve the ductility of a column is by repairing damaged reinforced concrete members by the external bonding of fiber reinforced polymer (FRP) laminates [8]. Moreover, strengthening of old RC structures is more economical than demolition and reconstruction. The use of FRP composites with an elongation * Corresponding author: m.elyoubi@est.umi.ac.ma http://dx.doi.org/10.28991/CEJ-2022-08-04-011 © 2022 by the authors. Licensee C.E.J, Tehran, Iran. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).