A new strengthening technique for increasing the load carrying capacity of rectangular reinforced concrete columns subjected to axial compressive loading

• Published in: Composites. Part B, Engineering Vol. 158; pp. 67 - 81
• Main Authors: Janwaen, Worajak, Barros, Joaquim A., Costa, Inês G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2019; Elsevier
• Subjects: Analytical model; Axial compressive loading tests; CFRP; Confinement; Engenharia Civil; Engenharia e Tecnologia; Prestress application; Prestress applications; RC columns of rectangular cross-section; Science & Technology; Analytical model; Confinement; RC columns of rectangular cross-section; Prestress application; CFRP; Axial compressive loading tests
• ISSN: 1359-8368; 1879-1069
• DOI: 10.1016/j.compositesb.2018.09.045

In this work, a new technique for the efficient confinement of reinforced concrete (RC) columns of rectangular cross-section is described and its effectiveness is assessed experimentally. This technique is based on the concept of applying strips of carbon fiber reinforced polymer (CFRP) wet layup sheets with a certain prestress level using a mechanical device. The influence of the cross-section aspect ratio of columns on the axial stress-strain response, strain field in the CFRP and strength increase provided by the different adopted strengthening configurations was investigated. All specimens had a height of 1100 mm, and three cross-sections were considered: 120 × 120 mm2, 240 × 120 mm2 and 480 × 120 mm2, representing cross-section aspect ratios (large/small edge) equal to 1, 2 and 4, respectively. Four types of columns were tested: conventional RC columns (reference columns), fully-wrapped columns, partially-wrapped columns, and columns strengthened according to the new technique. All columns were subjected to axial compression loading until failure. The experimental results show that the cross-section aspect ratio has a significant effect on the confinement effectiveness that CFRP strengthened systems can provide to RC columns of rectangular cross-section. The maximum axial strength and axial strain at the peak load of all columns significantly decrease when the cross-section aspect ratio increases. Based on the obtained experimental results, it is shown that the proposed technique is more efficient in terms of increasing the load carrying capacity of rectangular RC columns than CFRP-based conventional strengthening techniques. •A new technique (SC) for the confinement of RC columns of rectangular cross-section is proposed.•The efficiency of the SC technique was experimentally compared with FRP-based existing ones.•The proposed SC technique was more efficient than the fully- and partially-wrapped techniques.•Guidelines were adapted for predicting the strength of RC columns confined with the SC technique.•Good predictive performance was obtained for the proposed design guideline.