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

Transformed Section of LVL and Wood Joists

Transformed Section of LVL and Wood Joists

Transformed Section of LVL and Wood Joists

I want to sister an LVL to an existing wood joist.  Anyone ever calculate transformed section properties?  Do you think using the same method as a flitch beam is acceptable?
Any general thoughts on finding transformed sections?

RE: Transformed Section of LVL and Wood Joists

Why wouldn't you ratio the moduli like you do in any other transformed section? I thought that this was valid to all materials, all the time.

And just so I can sleep tonight - what is a flitch beam?
(Most of my experience has involved bridge structures, and sometime the terminology from other areas is new to me. I assume that this is a carpentry term?)

Sorry about the responding to a question with a question business, but I was curious on both points (transformed section and flitch beam).


RE: Transformed Section of LVL and Wood Joists

Since the Young's Modulous of the LVL and the sawn lumber are not that much different (largest ratio 2.0/1.0) it is not as noticable in the dimensions as steel (29.0/1.0).  Your LVL just takes a little larger share of the load for the same size members.  If you have DF (1.6E) wood and 1.8E LVL you don't even need to do the ratios. Use the dimensions directly to determine your section properties.  The E for wood is not as consistent as steel or other homogenious materials.  Actual E and published E varies a lot for sawn lumber.

RE: Transformed Section of LVL and Wood Joists

Holy Smokes! The design "guide" is 96 pages long!

I designed a flitched beam (just learned to word and I'm already throwing it around like I'm the king of flitched beams!) once for a friend of the boss (no, not my wife, the company president). The timber contribution was so insignificant, that I just ignored it. Of course, in that case, I added two steel plates to a timber beam, rather than one steel plate sandwiched between two pieces of lumber. But still, 96 pages?!!

All kidding aside, thanks for the post. I downloaded the guide and will keep it for future use.


RE: Transformed Section of LVL and Wood Joists

I ignore the wood and design the steel plates to take it all for a flitch beam.
As for sistering an LVL to an existing solid sawn, I was hoping for a conservative shortcut, instead of relative stiffness of each piece.

RE: Transformed Section of LVL and Wood Joists

Quick conservative design would be to use the properties of the original sawn lumber (Fb & E) and the crossection of the combined members.  In most cases it won't make much difference because you are constrained by the LVL and/or sawn lumber standard dimensions so it is all multiples of the allowable for one.  The question usually is do I have to add and LVL or sawn board to one side or both and how close of a nail or bolting pattern do I need.  The LVL manufacturer data usually gives you a conservative connection pattern.  5 minute job to size the sistered lumber. Buying a little more lumber is cheaper than engineering time. Most of the engineering time is spent determining whether the structure supporting beefed up beam is adequate.

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