§13.2 [F2.5] Bracing Members – Lateral Force Distribution

The unbraced length of a brace is considered to be the length between the nodes at the brace ends.

To perform the lateral force distribution checks on SCBFs, the engineer is required to assign the same frame number to all the braces in the same line of bracing. Also, the Use Frame Nos. to Designate a Frame Line option must be selected in the Seismic Code Dialog obtained by selecting the Criteria > Codes command.

The b/t ratios of stiffened and un-stiffened elements are checked per §8.2b against the compactness requirements in AISC 360 specification Table B4.1 and the requirements of 8.2 (Table I-8-1). Angles are only checked for the requirements of Table I-8-1.

AISC 341-16, AISC 341-10 Analysis of SCBF Columns

Member code check of SCBF columns follow the requirements of Section F2.3(i) where braces are assumed to resist forces corresponding to their expected strength in compression and tension and the requirements of Section F2.3(ii), in which braces in tension resist forces corresponding to their expected strength and braces in compression are assumed to resist their expected post-buckling strength.

To determine Emh for SCBF Column O, the effect of braces in frame lines A-O-B and X-O-Y are independently determined according to Section F2.3(i) and F2.3(ii). Frame lines A-O-B and X-O-Y are assumed to frame into the major and minor axes respectively of Column O. The tensile and compressive Emh values determined from the analyses are used in the load combinations for the applicable building code.