Shake table testing of tubular steel bracing members

Abstract

An experimental study on the seismic response of cold-formed steel tubular members functioning as bracing members in concentrically braced frames is described. A number of shake table tests were carried out to examine member and storey performance under earthquake loads. Three different square and rectangular hollow cross-sections were utilised for the bracing members. It is shown that maximum brace tensile forces can be over 30% higher than those estimated using the actual yield strength, due to strain hardening and strain rate effects. Moreover, the experimental storey shear can exceed that predicted by design procedures by more than 50%. The tests also indicate that the ductility demand under seismic loading can be estimated reasonably well for the frame models using a conventional equal-energy idealisation. In addition, the results illustrate generally satisfactory performance for braces with member slenderness exceeding typical limits in seismic codes.