Mechanics and validation tests of a post-tensioned self-centering brace with adjusted stiffness and deformation capacities using disc springs

Self-centering braces have been developed to reduce the residual deformation of steel frames in earthquakes. The brace has a higher elastic axial stiffness before the activation, which may result in a higher base shear for frame design. This work was aimed to develop a new post-tensioned self-centering brace (PT-SCB) with adjusted stiffness and deformation capabilities such that the brace could be designed based on a specified yield or ultimate frame drift. Combining disc springs and one of the compression members together in the original SCB could achieve new structural characteristics, providing an alternative to tune the axial stiffness and deformation. This work first introduces the mechanics and deformation mechanism of the proposed SCB and performs a parametric study to investigate the effect of disc spring stacks on the hysteretic response of SCBs. A test program is then conducted on cyclic tests of disc spring stacks in different serial and parallel combinations and two PT-SCBs. Each 3800 mm-long brace is composed of high-strength steel tendons, compression steel members, disc spring stacks, and bolted friction device. The hysteretic responses of the new SCB with different design parameters are used to validate the mechanics and ability of the axial stiffness and deformation adjustment.