Compressive behavior of circular CFST columns externally reinforced using CFRp composites: Fid-Bau Portal

Compressive behavior of circular CFST columns externally reinforced using CFRp composites

Ganesh Prabhu, G. / Sundarraja, M.C. / Kim, Yun Yong

Abstract Over the last several decades, various approaches to strengthening steel structures through the use of Carbon fibre reinforced polymer (CFRP) composites have been investigated; however, most of the studies have been focused on the steel tubes. This paper presents the feasibility analysis on the application of CFRP composite strips to strengthen the CFST column member under axial loading. CFRP strips having a width of 50mm were used to confine the columns. The experimental parameters were the spacing between the CFRP strips (20 and 30mm) and number of CFRP layers (one, two and three layers). All columns were tested under axial compression until failure. The experimental results revealed that bonding of CFRP composites effectively delayed the local buckling of the columns and also reduced the axial deformation by providing a confinement/restraining effect against the elastic deformation at both spacings. The confinement effect provided by CFRP composites was increased with the increase in the number of layers; however, the enhancement in buckling stress was not proportional. The load carrying capacity of the column increased with the application of CFRP strips, by up to 30% compared to the of un-strengthened column. From the test results it is suggested that the application of CFRP strips at a spacing of 20mm or 30mm is suitable for strengthening of a CFST circular column member; however, the application of strips at intervals of 30mm recommended as an economical approach to strengthening compared to the 20mm spacing. Finally, an analytical equation was proposed to predict the load carrying capacity of the CFRP strengthened CFST column, and the average difference between the calculated and experimental value was only ±5%.

Highlights • Experimental investigation was carried out to develop the optimum wrapping scheme for strengthening of circular CFST members. • CFRP strips were used to strengthen the CFST columns with two different spacing. • The results revealed that the CFRP strips bonding enhances the stiffness and load carrying capacity of the column. • Experimental results were compared with the proposed analytical model results.