On The Optimal Shape Of New Ductile KneeBracing

In this paper a particular structural bracing system, called the Chevron Knee Bracing (CKB), is introduced. In this framing system, a special form of diagonal braces that are connected to knee elements instead of beam-column joints is investigated. The braces provide required stiffness during moderate earthquakes, while the knee elements yield in flexure or shear to dissipate energy during a severe earthquake, whereby buckling of the braces or yielding of the main structure is prevented. First, elastic analysis is applied to the new system and a suitable shape and angle for the knee and the brace elements is proposed, using new and practical parameters. Then, by developing a nonlinear analytical model for the knee element in flexural and/or shear yielding mode, inelastic behaviour of the system is considered. Also, by using an energy calculation program as a subroutine in a dynamic FE program, a hysteretic energy calculation algorithm is devised and implemented for hysteretic analysis of the new structural bracing system. Finally, the optimal direction of the new framing system, which dramatically reduces the number of the active parameters and demonstrates a simple design technique, is investigated and developed.