Steel Tips from the Structural Steel Educational Council

Steel TIPS

12.1996 > Seismic Design Practice For Eccentrically Braced Frames

By Roy Becker and Michael Ishler

Seismic Design Practice For Eccentrically Braced Frames

This booklet is an update and revision of the Steel Tips publication on eccentrically braced frames dated May 1993 (ref. 16). The significant revisions to the May 1993 booklet are as follows: ? Design criteria is based on the 1994 Edition of the Uniform Building Code. The steel for the link beam element has a yield strength of 50 ksi. Based on current mill practices, this yield strength should be utilized for the capacity of the link beam for A36, A572 grade 50 and Dual Grade Steels. The use of a link adjacent to a column is not "encouraged." This is due to the moment connection required at the beam to column intersection and the possible difficulty in achieving a moment connection which can accommodate large rotations of the link subject to high shear and moment without significant loss of capacity. See Ref. 11 p. 333 for additional information. ? The beam outside the link has a strength at least 1.5 times the force corresponding to the link beam strength. It should be noted that ASTM and the Structural Steel Shapes Producers Council are in the process of writing a proposed "Standard Specification for Steel for Structural Shapes used in Building Framing." At the present time, this single standard would require that the following be met: yield strength = 50 ksi MIN; tensile strength = 65 ksi MIN; yield to tensile ratio = 0.85 MAX. However, these requirements are still under discussion and negotiation, but hopefully this single standard will be published by ASTM in the next year or two.

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