Biaxial restraint of axially loaded steel cores

The results from the testing of six short steel specimens are presented in this thesis to represent a portion of a full scale specimen of a solid steel round core confined by a steel tube, termed here as a biaxial restrained axially loaded steel core. The biaxial restrained axially loaded steel core is a first step in the development of a potentially effective restrained core for a Buckling Restraining Brace (BRB). In addition, four solid steel round bars are tested as controls to compare with the six short scale restrained specimens. Three objectives were explored in this study of the compressive behavior of a sleeved steel core. The first objective is to determine if a steel core restrained by a steel sleeve with a gap in between will have increased compressive properties and resist buckling. The second objective is to determine if a steel core restrained by a steel sleeve with a gap can increase the energy dissipation of the system compared to a solid steel round bar with the same dimensions. The third objective is to determine if lead foil placed between the two elements would act as a friction reducing mechanism, thereby minimizing the amount of axial load that would be transferred to the steel sleeve. The short steel specimens gained an increase of 45% to 48% in compressive strength compared to a core without a restraining sleeve. Energy dissipation increased with the sleeved compression members. Energy dissipation for the short steel specimens iv increased 85% to 246%. Lead was determined to be an appropriate intermediate material for applications requiring high early energy dissipation. The results of this study on six sleeved compression members and four solid steel round bars was a success and the objectives of the study were achieved.