H3.1 Scope
Composite eccentrically braced frames (C-EBF) shall be designed in conformance with this section. Columns shall be encased composite or filled composite. Beams shall be structural steel or composite beams. Links shall be structural steel sections. Braces shall be structural steel sections or filled composite members.
H3.2 Basis of Design
C-EBF shall satisfy the requirements of Section F3.2, except as modified in this section.
This section is applicable to braced frames for which one end of each brace intersects a beam at an eccentricity from the intersection of the centerlines of the beam and an adjacent brace or column, forming a link that is subjected to shear and flexure. Eccentricities less than the beam depth are permitted in the brace connection away from the link if the resulting member and connection forces are addressed in the design and do not change the expected source of inelastic deformation capacity.
C-EBF designed in accordance with these provisions are expected to provide significant inelastic deformation capacity primarily through shear or flexural yielding in the links.
The available strength of members shall satisfy the requirements in the Specification, except as modified in this section.
H3.3 Analysis
The analysis of C-EBF shall satisfy the analysis requirements of Section F3.3.
H3.4 System Requirements
The system requirements for C-EBF shall satisfy the system requirements of Section F3.4.
H3.5 Members
The member requirements of C-EBF shall satisfy the member requirements of Section F3.5.
H3.6 Connections
The connection requirements of C-EBF shall satisfy the connection requirements of Section F3.6, except as noted in the following.
H3.6a Beam-to-Column Connections
Where a brace or gusset plate connects to both members at a beam-to-column connection, the connection shall satisfy one of the following requirements:
- (a) The connection shall be a simple connection meeting the requirements of Specification Section B3.4a where the required rotation is taken to be 0.025 rad; or
- (b) Beam-to-column connections shall satisfy the requirements for fully restrained (FR) moment connections as specified in Sections D2, G2.6d, and G2.6e. The required flexural strength of the connection shall be determined from analysis and shall be considered in combination with the required strength of the brace connection and beam connection, including the diaphragm collector forces determined using the overstrength seismic load.