Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Steel Bracing Design

Steel Bracing Design

Steel Bracing Design

I am designing a steel bldg. with chevron and "x-bracing"  using a structural analysis/design computer program.
The bldg. columns have been analyzed with the bracing "inactive" to insure they will support all the gravity load.  My question is do I need to design the compression bracing for gravity load in addidtion to the lateral loads?  If I were designing the bldg. with tension-only bracing I would not be concerned with "failure" of the compression side brace in, for instance, an x-braced bay, but when I am relying on compression bracing to share the load with the tension brace it seems the compression brace needs to support all load it will see--including gravity loads.  Is this correct thinking?  Thanks for any suggestions.

RE: Steel Bracing Design

There are two philosophies for CBFs:

1) The compression braces are not designed to carry gravity loads. The compression braces are expected to buckle in a large seismic event and the gravity loads they were initially supporting will be transferred to the adjacent beams and columns.

2) The compression braces are designed for gravity loads.  This is a conservative approach.  If used, the beams and columns should still be designed to support the entire gravity load in recognition of the fact that the braces may buckle.

RE: Steel Bracing Design

Thanks for your response Taro.  The two philosophies you mentioned seem to be the predominate approaches I've run across in talking with others.  Some have said that if one were doing the analysis by hand calc's, gravity load in the bracing would not even be condidered, which is true.  It just seems to me that if your tension brace will not carry the full lateral load or your foundation cannot support the full shear load at one column, then your compression brace must be designed so that it will not fail under any loading, including gavity load--your compression brace cannot be in a buckled state when it must carry lateral load.

RE: Steel Bracing Design

Whether your design allows for brace buckling depends on the type of lateral forces.  You didn't mention if seismic resistance is required in your design.  My previous comments assumed earthquake loading because seismic resistance is now required in most of the United States.  If earthquake loads are not considered, the compression braces should be designed to preclude buckling.

If seismic design is required and you follow the code minimum design requirements, your compression braces will indeed buckle in a design-level event.   The lateral system is designed with a reduction factor that reflects the ductility and energy dissipation capacity of the system.  The design forces would have to be multiplied several times in order to preclude buckling.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close