Book Description

Abstract: "An experimental study was undertaken to investigate the cyclic strength and ductility of composite columns subjected to simulatedseismic loading conditions. Eight two-thirds scale specimens were tested, each consisting of a structural steel shape encased in reinforcedconcrete. Parameters studied in the test program included: the degree of concrete confinement required to achieve adequate ductility; the effectiveness of shear studs for developing flexural stiffness and capacity under combined loading; the distribution of transverse shear resistance among the elements of the composite column; and concrete compressive strength. The results of the test program indicate that composite columns possess exceptional ductility and strength under cyclic loading if the buckling of longitudinal reinforcement is inhibited. Furthermore, the steel shape provides the primary resistance to transverse shear during overloading, and shear studs are not effective in enhancing the resistance against lateral loading. The elastic secant stiffness of the composite section corresponding to initial yielding of the longitudinal reinforcement was found to be well approximated by using one-half the gross moment of inertia (0.5I[subscript g]) in conjunction with Young's modulus for concrete. A prediction method based on superimposing the individual strengths of the reinforced concrete and structural steel shape was found to provide good agreement with test results. Current AISC LRFD provisions were determined to grossly underestimate the flexural capacity of the test specimens, which were axially loaded to 20% of their nominal pure axial load capacity [sic]."