Effective Length Factor for Discontinuous X-Bracing Systems

In this paper the elastic stability analysis of X-bracing systems is performed. Special attention is focused on the effect of midspan (center) connection on the out-of-plane buckling load of these systems. Commonly, in practice, one of the diagonal members is discontinuous at the midspan intersection and a gusset plate is used to connect the members. So the center connection is modeled as partly pinned or semirigid. In this study the closed-form relationships are obtained for the evaluation of effective length factor of X-bracing with pinned end connections and either pinned or semirigid (discontinuous) midconnection. The tension and compression diagonals are assumed to have different section properties and axial loading. The results are graphically displayed for some practical cases. Three types of double angles X-bracing with different detailing for midconnection are compared. The numerical results show that the discontinuous center connection can affect the buckling load and effective length factor of diagonal members and it should be considered in the design of X-bracing systems.