DESIGN METHOD AND MECHANICAL PROPERTIES OF CIRCULAR PARALLEL BUCKLING RESTRAINED BRACE

In this study, a circular-section parallel buckling restrained brace (CP-BRB) is proposed, which consists of two parallel resistance systems, the internal and external resistance systems, and a lot of miniature shear dampers with very small yield displacement distributed at both ends of the external resistance system. According to the working principle of CP-BRB, a simplified mechanical model of CP-BRB is established, and a simplified design method for CP-BRB including the calculation formulas of axial stiffness, yield bearing capacity and yield displacement are derived upon the optimal failure mode. Based on a variety of traditional BRB specimens in literatures, three sets of CP-BRB examples were designed, and their mechanical properties and failure modes were studied by ABAQUS. The results show that: The yield displacement of a large number of miniature shear dampers is much smaller than the yield displacement of the internal round steel rod, and the mechanical properties of CP-BRB have a significant staged yield characteristic; The hysteretic curve of CP-BRB is full, which implies that CP-BRB has good ductility and energy dissipation capacity. Under the action of axial force, the parallel internal and external resistance system can form two resistance lines; The yield displacement of CP-BRB is equivalent to 8%~29% of the traditional BRB, which exhibits that: CP-BRB may develop into the plastic state much earlier than the traditional BRB under earthquake action and better protect the main structure, and engineering application prospects is well-hoped; The results obtained by the formulae agree well with the finite element results, and the proposed calculation formulas presented are reliable and can be used in engineering practice.