April 19, 2016

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

Tags: Seismic, New, RISAConnection, Brace Connection

May 25, 2016 | Seismic, New, RISAConnection, Brace Connection

SCBF Seismic Brace Connections

Vertical Diagonal Brace connections and Vertical Chevron Brace connections may be designed as Special Concentric Braced Frame (SCBF) connections in RISAConnection v6. Basis of Design RISAConnection designs SCBF per the provisions found in section F2 of the AISC Seismic Provisions for Structural Steel Buildings (AISC 341-2010). SCBF systems are very similar to OCBF connections; however they include additional detailing requirements to direct ductile behavior into the braces. These detailing requirements provide for greater energy dissipation and ductility which means SCBF can be designed to a lower force level to that of OCBF connections. Basic Requirements The requirements for SCBF systems per the AISC 341-10 include the following: Columns and Braces are designed as highly ductile members. Beams are designed as moderately ductile members. Brace members are limited to a slenderness of KL/r ≤ 200. Brace connections must be designed to withstand the flexural forces imposed by brace buckling. Connection strength requirement which ensures that the brace member acts as a ductile link in the frame prior to the connection failing. Two analyses must be considered; one where both braces are assumed to resist their expected strength, and the other where the compression brace is assumed to have already buckled. Design…

June 28, 2016 | Seismic, New, RISAConnection, News, Brace Connection, Integration

Seismic Brace Connection Integration with RISA-3D

RISAConnection version 6.0 has introduced the ability to design vertical brace connections per the seismic design provisions of the AISC 341-10 Seismic Design Manual. Now you can export Vertical Diagonal Brace Connections and Vertical Chevron Brace Connections from RISA-3D into RISAConnection as either Ordinary Concentric Braced Frames (OCBF) or Special Concentric Braced Frames (SCBF). See post for information on How to Model a Seismic Vertical Brace Connection in the stand alone version of RISAConnection. Link: Seismic Brace Connections now Available RISA-3D Input and Design: 1. First, you must create and apply a Seismic vertical brace Connection Rule to your member in RISA-3D. The application rules are the same as for non-seismic vertical braces. 2. You must also create and apply an appropriate Seismic Design Rule. For OCBF, select a “Minimal” Frame Ductility. For SCBF, select “High” Frame Ductility. 3. Solve the RISA-3D model. Note that you must solve for RISA-3D Seismic Detailing results. If your solution does not include Seismic Detailing results, you will not be able to export the correct brace axial forces into RISAConnection. 4. Solve the Connections within RISA-3D to see a summary of the connection design. 5. For details on the connection design, use the Director…

March 31, 2016 | Seismic, New, RISAConnection, Brace Connection

OCBF & SCBF Seismic Brace Connections now Available

RISAConnection v6 has introduced the ability to design vertical brace connections per the seismic design provisions of the AISC 341-10 Seismic Design Manual. Now you can designate Vertical Diagonal Brace Connections and Vertical Chevron Brace Connections as either Ordinary Concentric Braced Frames (OCBF) or Special Concentric Braced Frames (SCBF). To create the model: 1. First, select the type of vertical brace connection that you want to use. 2. On the General tab of Connection Properties, select your type of Seismic System. 3. Enter in the other applicable variables for seismic design. OCBF: Brace Length, Brace Length Effective Length Factor, K, and the Ca Beam Ratio which is used to calculate the beam width to thickness ratio per AISC 341-10 Table D1.1. SCBF: Gusset Plate Clearance method, Brace Length Effective Length Factor, K, and the Ca Beam Ratio which is used to calculate the beam width to thickness ratio per AISC 341-10 Table D1.1. 4. Once you have designated the connection as seismic, you will also see that you have inputs for Brace Tensile Axial force and Brace Compressive Axial RISAConnection will design braces for both tension and compression forces at the same time. 5. The results report will reflect the…