Issam E. Harik

Strength of Rectangular Concrete Columns Reinforced with Fiber-Reinforced Polymer Bars

The strength interaction behavior of fiber-reinforced polymer (FRP) reinforced concrete (RC) columns is presented using an ultimate strength approach. A numerical integration technique is used to examine the slenderness effects of columns. The authors demonstrate that FRP RC columns have a propensity to undergo brittle-tension failure. This failure is generally sudden, and is associated with tension rupture of FRP bars when the strain in outer bar layer reaches or exceeds its ultimate load at the same time, or before, the concrete reaches its ultimate strain in compression. For RC columns reinforced with FRP bars, the current American Concrete Institute’s ratio limits may not be adequate.

Minimum Reinforcement Ratio for Fiber-Reinforced Polymer Reinforced Concrete Rectangular Columns

Two failure mechanisms were identified through a strength interaction analysis of rectangular concrete columns reinforced with fiber-reinforced polymer (FRP) bars. While the failure mechanisms identified were premature-compression failure and brittle-tension failure, the study demonstrated that, due to the low ultimate tensile strain for FRP bars, the brittle-tension failure was more likely to occur. Interaction design diagrams provide the process for identifying a reinforcement ratio that is greater than a minimum required ratio, which will identify the failures, and prevent brittle-tension failure. The authors recommend that only FRP reinforcing bars with ultimate compression strains larger than the concrete compression strain should be used in column applications.