Title: Variable Cylindrical Concrete Confined by Carbon Fiber- Reinforced Polymer under Axial Compression

Author(s): Yail J. Kim and Aliasghar Hassani

Publication: Structural Journal

Volume: 120

Issue: 4

Appears on pages(s): 89-102

Keywords: carbon fiber-reinforced polymer (CFRP); confinement; rehabilitation; strengthening; variable cross sections.

DOI: 10.14359/51737340

Date: 7/1/2023

Abstract:
This paper presents the axial behavior of cylindrical concrete with variable cross sections confined by carbon fiber-reinforced polymer (CFRP) sheets. The test specimens are classified into three conformational categories: right angles (Type 1), truncated cones (Types 2 and 3), and barrels (Types 4 and 5), which are subjected to a preload level of 0%fc′, 30%fc′, and 60%fc′ (fc′ is the compressive strength of plain concrete) for the representation of existing damage in core concrete prior to wrapping with CFRP. The average capacity of the confined concrete in Type 1 is 106% higher than that of its unconfined counterpart. With an increase in the taper angle, the axial resistance of Types 2 and 3 is improved due to the enlarged base areas; however, the expanded bellies along the height of Types 4 and 5 lower the capacity by reducing the confining pressure of the CFRP sheets. Although the adverse effects of the preloading are evident in the context of reserved reliability and damage evolution, the validity of the confinement system is preserved from a strengthening standpoint. The geometric attributes dominate the load-displacement relationships, post-peak deformations, energy dissipation, and failure characteristics of the specimens. Analytical modeling clarifies that, compared with other parameters, the thickness of CFRP is the salient factor influencing the confining pressure of the system. According to the principle of energy conservation, a simplified design proposal is suggested to calculate the strength of the confined nonprismatic concrete.