Built Up Column w/ 2x8's??? 1

[rnorth]

Does anyone have any design tables or guides for designing bult up columns?

 

[dik]

I use woodworks... works very well.

 

[henri2]

Check out this thread

http://www.eng-tips.com/viewthread.cfm?qid=142933

 

[twinnell]

Enercalc...its free for the demo version, which is the full blown version.

 

[SlideRuleEra]

Download some of Dr. Bohnhoff's publications

http://bse.wisc.edu/bohnhoff/publications.htm

http://www.SlideRuleEra.net

 

[rnorth]

I'm trying to get 6x6 columns to work for a pole barn addition, here are my parameters:
select str, treated SPF Fc=1400psi E=1.5x10^6psi
length is 12' w/ fixed base and sidesway permitted so Ke=2.1
loads are snow 85 psf and DL 15 PSL (2/12 monotruss @ 16" oc). each post carries 8500 lbs.
Ke*l/d = 2.1*12*12/5.5 = 55"
classified as a long column so F'c=.3E/55^2 = 149psi

this number seems very small, and a column design table I got from an AWC publication gives 399psi allowable stress for E and Fc listed above w/ 56 l/d but this same publication mentions not to use columns w/ l/d > 50.

with the first method I can get 8x8 to work, does anyone have any advice or find something I am doing wrong? TIA

 

[civilperson]

Detail the top of the column to be held at 90 degrees to the horizontal, (rather than pinned, which give the Ke of 2.1), thus allowing a lower Ke of 1.2<Ke<2.0. This should help somewhat.

 

[MiketheEngineer]

Beamchek at

http://www.beamchek.com

is a very good program for doing all kinds of beams and columns. Only a $100 or so.

 

[MiketheEngineer]

BTW -

Get rid of the side sway if you can by using shear walls or bracing or whatever. I show a 6x6 very good with Ke = 1

 

[rnorth]

in the direction parrallel to the wall the columns are fully braced becasue of the wall sheathing. however in the other direction the posts carry LVL beams which support monotrusses at 16" so I can't see how i would prevent sidesway in that direction because of course that is the open area underneath the addition. I'm going to add diagonal 2x6 bracing in the ends walls.

 

[rnorth]

thanks for the beamcheck suggestion, MIke, that helped me verify what I was doing. not sure if i will purchase it or not, seems like a fair price for $150.00

 

[twinnell]

Try Enercalc...it's free.

 

[rnorth]

thanks, I will try it.