New Hybrid FRP Strengthening Technique for Rectangular RC Columns Subjected to 1 Eccentric Compressive Loading 2 3 Worajak Janwaen a,b , Joaquim A. O. Barros c and Inês G. Costa d 4 5 a PhD Candidate, ISISE, Department of Civil Engineering, University of Minho, Azurém 4800-058 6 Guimarães, Portugal, tontrakarn.w@gmail.com (corresponding author) 7 b Lecturer, Department of Civil Engineering, University of Phayao, Thailand 8 c Full Prof., ISISE, Department of Civil Engineering, University of Minho, Azurém 4800-058 9 Guimarães, Portugal, barros@civil.uminho.pt 10 d PhD Civil Eng., CiviTest, Parque Industrial de Jesufrei, Rua da Indústria, n.º144, 4770-160 Vila 11 Nova de Famalicão, Portugal, inescosta@civitest.com 12 13 Abstract 14 In this work, a new hybrid technique for the strengthening of rectangular reinforced concrete (RC) 15 columns under eccentric compressive loading is described, and its effectiveness is assessed 16 experimentally. This technique combines two carbon fiber-reinforced polymer (CFRP) systems for 17 complementary purposes: strips of CFRP wet-layup sheets with a certain prestress level using a 18 mechanical device in an attempt of introducing an effective concrete confinement; CFRP laminates 19 applied according to the near surface mounted (NSM) technique for increasing the flexural capacity of 20 the RC columns. The effects of the cross-section aspect ratio and flexural strengthening ratio of CFRP 21 laminates were investigated in terms of the load carrying capacity of this type of RC columns. All 22 specimens had a height of 1080 mm, and three cross-sections were considered, 120×120 mm 2 , 240×120 23 mm 2 and 480×120 mm 2 , representing cross-section aspect ratios (large/small edge) equal to 1, 2 and 4, 24 respectively. All columns were subjected to eccentric compressive loading until failure. The results 25 showed that the new hybrid strengthening technique can enhance the performance of rectangular RC 26 columns in terms of load-carrying capacity and ductility under eccentric loading. The cross-section 27