Allowable Wood Arch Deflection 2

[msquared48]

Anyone know any good guidelines for vertical and lateral deflections of the main menber of a semi-circular wood arch section? Unbalanced snow load is killing me here!

Mike McCann
MMC Engineering

 

[diarmud]

Checked the 2005 NDS, probably me but can't find anything.

1994 AITC Timber Manual, 4th Edition says "Specific deflection limitations forarches have not been generally established becaseu this is a function of the intended use."

Sorry can't help,
Good luck and let us know what you find/decide.
Dermott

 

[boo1]

https://www.aitc-glulam.org/shopcart/Pdf/aitc tn_23.pdf

 

[msquared48]

Kinda what I found too. Great when your #$% is hanging in the wind..

I was wondering about linking the deflection to the "snap-through" mode of failure as in Timoshenko and Gere, but that's idea's way out on a limb and too complicated for this problem. I will keep looking. Thanks. You have confirned that I am not crazy...yet.

Mike McCann
MMC Engineering

 

[RARWOOD]

Although I have done a lot of research on this topic I have not been able to find any published guide lines on arch deflection.

It is mainly a problem of how much deflection can the attached finish material handle. A retired engineer I know with over forty years of experience in wood design, indicated before computers generally arch deflections were not calculated because the process was very time consuming and most people did not have a lot of faith in the final results.

He indicated the engineers he worked with thought that the decking would reduce the arch deflections. In some case, where he ran the numbers, he thought the results were close to what he observed in the field. In addition he indicated that he saw a lot of cmu walls that were not plumb because of arch deflection.

 

[diarmud]

http://www.aitc-glulam.org/shopcart/Pdf/aitctechnicalnote02.pdf

Try this, may not be right on but may give you some ideas.

Good luck,
Dermott