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

eccentric moments in trusses

eccentric moments in trusses

eccentric moments in trusses

In a plane truss, if the members' Centroidal gravity line are not coinciding in one point at a node, there will be eccentricity of forces and hence moments developed.
How to distribute this local moment in the global truss.
Can anybody give some suggestion?

RE: eccentric moments in trusses

Hi Kags,
The moment is usually distributed into the chord each side of the joint as the bracings are considered pinned and chord continuous.
The moment is the combined horizontal component of the braces (along the axis of the chord) is multiplyed by the eccentricity ( distance between the chord centreline and point at which the bracings centrelines cross).
This is then split into the chord each side of the joint with regard to the chord stiffness (I/LE)
where I = chord second moment of area
and LE = chord effective length
Chord SHS 150x150x10 S355 EN10210 I=1773 cm^4
Two Braces at 45deg. to chord forming K-joint with 6mm eccentricity.
Brace 1 = 267 kN Tension
Brace 2 = 300 kN Comp
Effective length of chord side 1, LE1 = 270cm
Effective length of chord side 2, LE2 = 135cm
Horiz component of braces, F = 267 cos 45° + 300 cos 45°
F = 401 kN    (both acting in same direction so added)
Moment due to eccentricity, M = 401 x 0.006 = 2.406 kNm
Chord side 1 stiffness = I/LE1 = 1773/270 = 6.57
Chord side 2 stiffness = I/LE2 = 1773/135 = 13.13
Moment chord side 1 = 2.406 kNm 6.57/(6.57+13.13)= 0.80 kNm
Moment chord side 2 = 2.406 kNm 13.13/(6.57+13.13)= 1.60 kNm

Hope this helps

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