The development of the buckling restrained braces with new end restrains

Abstract

This paper presents an experimental investigation of buckling restrained braces (BRBs) with new end restraints and casing members (CMs). The component tests for ten BRBs with CMs consisting of concrete-filled steel tube (unbonded), plain concrete, plain concrete wrapped with Fiber-Reinforced Polymer (FRP), reinforced concrete and a built-up section were tested up to a core plate (CP) strain of 2.0%. In unbonded BRBs, an unrestrained part is usually available on the CP. This part may be a candidate for buckling during cyclic excursions. Hence both ends of the BRBs at the unrestrained part of the CP need to be restrained more effectively. The innovations of BRBs in the present study were that additional end restraints were added at the unrestrained part of the CP at both ends, isolation material was employed, and a more economical CM was used. These new end restraints consisted of hollow steel sections and steel plates welded to each other and were attached to the CM. The testing of the improved BRBs indicated that the cyclic performance of the BRBs was satisfactory up to a CP strain of 2.0%. The energy dissipation capacity of the BRBs was found to be significantly dependent on compression strength adjustment factor, β, and strain hardening adjustment factor, ω. Consequently, the improved BRBs with sufficient stiffness to resist out-of-plane buckling at both ends have acceptable cyclic performance according to the test results. Furthermore, the connection details namely slip critical, isolation materials, and their application techniques have also been investigated for the improved BRB design in this study.