Design for slenderness in concrete columns internally reinforced with fiber-reinforced polymer bars

Despite their successful introduction into the construction market, widespr ead acceptance of fiber-reinforced polymer (FRP) reinforcement by the engin eering community depends on timely development of design guidelines and spe cifications. Low stiffness, high tensile strength, low compressive strength , and linear-elastic response of FRP reinforcement can influence slendernes s of FRP-reinforced concrete (RC) columns. A rational method is developed f or the analysis of slender FRP-RC columns. A detailed parametric study is c arried out by varying the type of reinforcement (yielding or nonyielding ba rs), reinforcement ratio, ratio of elastic moduli of reinforcement and conc rete, ratio of strengths of reinforcement and concrete, ratio of compressiv e and tensile strengths of reinforcement, eccentricity ratio of the axial l oad, and column end eccentricity, slenderness, and curvature. This study re commends reducing the current slenderness limit of 22 to 17 for FRP-RC colu mns bent in single curvature. It is also shown that the moment magnificatio n method can be extended to FRP-RC columns. The current stiffness formulas and the stiffness reduction factor however need to be adjusted either as so le functions of modular ratio or as functions of both modular ratio and ecc entricity ratio.