Wood Column Info By Ryan B.

[glenn kangiser]

Ryan has been kind enough to give us a posting with some general column information.  Great info to make that barn add on etc. a little safer.  I copied it here to be more easily found.  In general many types of soil from some of my past jobs would support around 2000 lbs per square foot but your type may vary.  The area of the concrete footing would have to be large enough to support the given load.   Thanks again Ryan

        Re: Engineering - For beginners, Part 6
« Reply #2 on: Today at 10:43am »       

4x4 8' 6000 lbs
4x4 <14' 2000 lbs
 
6x6 8' 24000 lbs
6x6 <22' 5000 lbs
 
12x12 8' 128000 lbs
 
#2 D.F.  
Both ends in a "nonconstraining" style of connection.
No crown.
Free of heart center.
Unbraced (not attached to any portion of wall) for full length.
Ignorance factor +25% is included in max loads.
 
Beam design of this type takes the stress factor as limiting element, deflection is ignored.
Shorter lengths vs. weight can be interpolated from given maximums above.
Pier size can often be the controlling variable in the upper limits of column design rather than weight due to the cost and complexity of large piers.  
4x4 at 8' is close to a required double trimmer in building design codes.
Often taller posts are specified as GLB or a manufactured style of post.
Braced posts (attached to some type of wall sheeting) loads can be higher.
Not given in design formula is a location correction factor that should be included if they are placed where cars might impact post.
 
 
The wood column formula has 13 or so variables. It's usually given in two parts because of its length!
 
Sawn or G.L.
Shape
Size
End Connections 3 types
Braced length
Size factor
Buckling factor 2 types
Fiber stress perpendicular to grain
Modulus of Elasticity
Variable slenderness ratio