PERFORMANCE TESTING OF BUCKLING-RESTRAINED BRACE WITH I CROSS SECTION UNRESTRAINED SEGMENT

摘要

The hysteretic behavior of four buckling-restrained braces (BRBs) with I cross section unrestrained segment were tested under cyclic load. The transformation of the unrestrained segment's section from crisscross shape to I shape can significantly improve the moment-resistance capacity of the unrestrained segment, avoiding buckling instability effectively due to sudden enhancement of stiffness. The load-carrying element of BRB was fabricated with steel (Chinese Q235), and four layers of plastic film (0.2 mm in thickness) were used as unbonded materials to provide space to prevent the buckling of inner core in higher modes and facilitate its lateral expansion in case of compression. In the process of experiment, BRBs did not buckle, and there is an obvious strain intensification in both tension and compression phases; the ductility of brace also increases markedly. BRBs could undergo fully-reversed axial yield cycles without loss of stiffness and strength, and the energy absorption was good. The resilience model can be simplified to a symmetrical bilinear resilience model.