New Hybrid FRP Strengthening Technique for Rectangular RC Columns Subjected to Eccentric Compressive Loading

Abstract

In this work, a new hybrid technique for the strengthening of rectangular reinforced concrete (RC) columns under eccentric compressive loading is described, and its effectiveness is assessed experimentally. This technique combines two carbon fiber-reinforced polymer (CFRP) systems for complementary purposes: strips of CFRP wet-layup sheets with a certain prestress level using a mechanical device in an attempt of introducing an effective concrete confinement; CFRP laminates applied according to the near surface mounted (NSM) technique for increasing the flexural capacity of the RC columns. The effects of the cross-section aspect ratio and flexural strengthening ratio of CFRP laminates were investigated in terms of the load carrying capacity of this type of RC columns. All specimens had a height of 1080 mm, and three cross-sections were considered, 120×120 mm 2 , 240×120 mm 2 and 480×120 mm 2 , representing cross-section aspect ratios (large/small edge) equal to 1, 2 and 4, respectively. All columns were subjected to eccentric compressive loading until failure. The results showed that the new hybrid strengthening technique can enhance the performance of rectangular RC columns in terms of load-carrying capacity and ductility under eccentric loading. The cross-section aspect ratio played an important role on the confinement effectiveness of the strengthened system. When the cross-section aspect ratio increases, the benefits provided by the proposed technique in terms of maximum axial strength and lateral deformability at the peak load of all columns decrease. The load carrying capacity and lateral deformability of the tested RC columns have increased with the flexural strengthening ratio. Moreover, an analytical model is proposed for evaluating the maximum strength and the axial load-lateral displacement response of rectangular RC columns strengthened according to the new proposed technique, and a good predictive performance was obtained.

Generalized Analysis-oriented model of FRP confined concrete circular columns

“…Barros and Ferreira [6] evidenced that by increasing s f , the axial and dilation responses of FPC drove to be similar to those of unconfined concrete (UC), as verified by Zeng et al [7]. For the case of FPC, Guo et al [8,9] and Janwaen et al [10,11] showed that concrete at the middle distance between two consecutive FRP strips, known as critical section, would be subjected to the maximum transversal deformation in comparison with the concrete expansion at the strip regions.…”