×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Truss for softwood

Truss for softwood

Truss for softwood

(OP)
Hello. I'm new here and I found this site greatly helpful to fresh engineers like me. Currently I'm testing few trusses made from relatively light and soft timber. Although they passed minimum requirement for strength, deflection etc given in Standards (BS and AS), they still generally failed at the member. Is it possible or practical in real situation to reduce the length of members by introducing more joints/splices to force the failure to the joints instead?

Expert opinions and any suggestions are deeply appreciated. Sorry for the language...

RE: Truss for softwood

What is the failure mode and size on the failed members?

RE: Truss for softwood

(OP)
The main members (rafter and ceiling) are 35x100 (mm). 5m span truss with 17.5 and 22.5 pitch. Mostly shear failure at rafter but some rafter seems to "buckle" when we look from the side... thanks

RE: Truss for softwood

Continuous bracing such as a roof diaphragm, or closely spaced purlins would dramatically increase the strength of the top chord by reducing the buckling. Also, look at the way that the chords are connected at the truss ends, you may be creating a high shear concentration there.

RE: Truss for softwood

(OP)
Thanks for the advice Doc. Is there any other way to increase the strength, that is normally applied in actual situation nowadays?

RE: Truss for softwood

It seems to me your testing is showing you that your design is not adequate, either in spans or sizes of members.  Adding continuous lateral bracing will reduce lateral buckling, as will adding members onto the buckling ones in a "T" fashion.

You can add more members (and joints) to reduce stresses.  I don't mean to be disrespectful, but it sounds as if your need to go back to statics basics.  Or, accept your test results as providing you good info, and react accordingly.

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!


Resources