Calculating deflection in SCL

[masterdesign]

I looked for a thread on this but didn't see anything. If this has already been discussed, please kindly post a link.

Just noticing this in TJ-9000:

I use excel spreadsheets to calculate my beams. Does anyone have a reference for calculating bending + shear deflection for other loading conditions (point loads, partial uniform loads, cantilevers, multi-span)?

 

[ChorasDen]

There are a couple ways to approach this. If you want the quick, easy, but not always 'correct' way, you can approximate the contribution for shear deflection by multiplying the member Modulus by 0.95. This is generally a good approach for uniformally loaded members, but can cause incorrect calculations for shear deflection when members have multiple or large point loads.

Keep in mind what causes shear deflection isn't the magnitude of the shear itself, but the differential of shear across the area in question.

Don Bender has a research paper that discusses a bit of the derivation and how to approach, I'll include a photo below of how to find it.

 

[Celt83]

This text on Timoshenko Beam Theory covers most loading conditions: Link
The tricky part may be determining what the shear area is for the SCL, you could likely back into a possible solution using the manufacturers listed equation.

 

[masterdesign]

Thanks for the great references! I will review.

 

[lexpatrie]

For convenience:

Shear Deflection of Composite Wood Beams, Skaggs, Bender, Wood and Fiber Science, July 1995.

 

[STpipe]

I recently had to do this, and referenced the following article:

https://support.clearcalcs.com/article/198-shear-deflection-in-wood-beam-calculators

If I recall, I expanded on the formulation in the article and arrived at the same formula as the one contained in the TJ-9000 literature.

 

[lexpatrie]

I've added this to the FAQ. The title of the FAQ is perhaps not the best, but it's accurate as it's the title of the article I refer to anyway.

https://www.eng-tips.com/faqs.cfm?fid=2813

Regards,
Brian

 

[XR250]

I just assume I am about 10% off in my results if I ignore the shear deflection in the calcs.
I never design anywhere near the the bottom of the deflection barrel anyway so it does not really matter.
Time is money.