A model for increasing the distances and decreasing the dimensions of stiffeners for tubular link beams in eccentrically braced frames

Tubular cross-sections of link beams have substantial torsional stability, making them less susceptible to lateral torsional buckling than I-shaped cross-sections in eccentrically braced frames, and may thus not require lateral bracing. Web of I-shaped cross-sections because of having clamped boundary conditions in its four sides than web of tubular cross-sections that have simply supported boundary conditions in its four sides, having advantage. In this study, link beams with different tubular and I-shaped cross-sections in non-elastic limits are investigated and has been tried by changing link beams stiffeners array cause increasing the distances and decreasing the dimensions of them. For this purpose nonlinear finite element software and AISC-2005, loading protocol are used.The numerical result of different link beams models indicate that tubular and I-shaped cross-sections if having same geometric profile, I-shaped cross-sections have higher rotation capacity because of better performance of their web. So study of results indicate that new arraying of stiffeners of tubular link beam inceases increasing the distances and decreasing the dimensions of them and doesn’t have any bad effect on rotation angle capacity of them. An investigation of the effect of stiffener dimensions indicated that stiffeners dimensions if having minimum area and moment of inertia requirements don’t effect on rotation angle capacity.