Title: Behavior of Concrete-Filled Hollow Structural Section Beam Columns to Seismic Shear Displacements

Author(s): Made S. Hardika and N. J. Gardner

Publication: Structural Journal

Volume: 101

Issue: 1

Appears on pages(s): 39-46

Keywords: beam-column; concrete; ductility; seismic

DOI: 10.14359/12996

Date: 1/1/2004

Abstract:
This paper describes an experimental program to study the seismic resistance of concrete-filled hollow structural section (HSS) columns using normal- and high-strength concrete (40 and 100 MPa [5800 and 14,500 psi]), respectively. Twenty-four concrete-filled, 8 in.2 (203 mm), steel hollow-structural section, beam-column specimens were tested under constant axial compressive load and cyclic horizontal displacement. The lines of action of the horizontal displacements were either square, normal to a conventional axis, or across a diagonal. The experimental investigation included determination of strength capacity, ductility, and flexural stiffness of concrete filled steel tube (CFT) beam-columns for compact (section dimension/ thickness b/t = 21) and slender (b/t = 43) HSS sections. All HSS CFT columns tested exhibited excellent hysteretic behavior. Maximum moments occurred at drifts of 2 to 3% and ultimate drift ratios exceeded 7%. No local buckling before yielding was observed. The moment capacities of HSS CFT columns loaded with the plane of bending across the diagonal were only slightly less than those loaded with the plane of bending parallel to a square side, reducing the need for elaborate procedures to calculate the moment capacities at orientations between 0 and 45 degrees. The strength may be calculated using conventional section analysis with a rectangular stress block extending the full distance from the surface in compression to the neutral axis and a concrete strength of a1a2a3f¢c, where a1 is a factor related to concrete strength, a2 is related to t/b, and a3 is related to the rate of loading.