OCBF Seismic Brace Connections

Vertical Diagonal Brace connections and Vertical Chevron Brace connections may be designed as Ordinary Concentric Braced Frame (OCBF) connections in RISAConnection v6.

Basis of Design

RISAConnection designs OCBF per the provisions found in section F1 of the AISC Seismic Provisions for Structural Steel Buildings (AISC 341-2010).

OCBF systems anticipate little inelastic deformation and are designed using a higher seismic force level to account for the limited system ductility.

Basic Requirements

The requirements for OCBF systems per the AISC 341-10 include the following:

• Braces are designed as moderately ductile members.

• Chevron brace members are limited to a slenderness of KL/r ≤ 4*√(E/Fy).

• Connection strength requirement which ensures that the brace member acts as a ductile link in the frame prior to the connection failing.

Design Results

RISAConnection calculates the required design strength of the braces in tension and compression and presents the full results on the new Seismic tab of the results report. The results can include the following detailed calculations and checks:

• Controlling Load Calculation

• Seismic Loading Combinations

• Seismic Load Distribution Calculations

• Seismic Workpoint Limitations

• Seismic Yield Stress Limitations

• Seismic Brace Slenderness

• Seismic Brace Width to Thickness Ratios

• Seismic Weld Limitations