Coreless self-centering braces as retrofitting devices in steel structures

Conventional lateral resisting systems can provide sufficient strength and ductility for design based earthquakes, although the considerable residual deformation remaining in the plasticized regions undermines the resiliency of the structures. In order to resolve this problem, various self-centering systems have been proposed and tested in recent years, most of which are specified for new buildings and are not simply suitable for retrofitting applications. Moreover, the available self-centering systems are costly and complex to assemble, which can be considered as a serious barrier for practical application. To address these drawbacks, an innovative Core-Less Self-Centering (CLSC) brace is proposed, which is specified as a retrofitting device to be used in conjunction with conventional lateral resisting systems. CLSC braces are devices which can minimize residual deformations of existing buildings by combination of a nonlinear elastic behavior with the nonlinear inelastic behavior of the conventional resisting frames. A parametric study is conducted to find the most cost effective materials and at the same time, full self-centering behavior, using OpenSees software. During the second phase of study, an optimal design method is developed to achieve the most efficient configuration for the proposed braces among structural elements. In this regard, an iterative procedure is implemented on a 9-story steel plate shear wall (SPSW) building, which is retrofitted with CLSC braces, using Nonlinear Response History Analysis (NRHA), and the structural responses are evaluated. Results illustrate that the proposed brace not only is individually more economical, but also a wise placement of braces can enhance structural resiliency. The implementation of CLSC braces can significantly reduce repair costs of the whole structure, with minimal manipulation of the structural performance parameters.