Tubular links for eccentrically braced frames. II: Experimental verification

This paper describes the results of an experimental study to verify proposed design requirements for eccentrically braced frame links with hollow rectangular (i.e., tubular) cross sections. Twelve primary link specimens and two supplementary links that have different end connections are tested. Three cross sections and four normalized link lengths are considered. Two of the cross sections have web and flange compactness ratios near the proposed limits while the third cross section has compactness ratios significantly less than the proposed limits. Shear, intermediate, and flexural, link lengths are tested, including some at the critical transition length from shear-to-intermediate link behavior. Results indicated that tubular links satisfying the proposed compactness and stiffener requirements can achieve the target plastic rotations for wide-flange links when subjected to the loading protocol specified in the 2005 AISC Seismic Provisions. The predominant failure mode is fracture of the link flange near the connection to the end plates used for testing. A method for calculating the ultimate link shear, proposed by others for wide-flange links, is also investigated and modified to agree with the results of the tubular link tests.