# beam pocket bearing



## darcar (May 7, 2012)

We see a few different methods of bearing in beaqm pockets under beams (LVL's, steel, etc.)

When it comes to treated wood, we've seen them laying flat (1-1/2" tall and 3-1/2" wide) or standing like a stud but today for the first time I saw one turned in the direction where the 3-1/2" was up and down.  Does anyone have info stating the bearing capacity of lumber pending the orientation of the lumber?

Thanks in advance


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## syarn (May 7, 2012)

http://www.awc.org/pdf/WSDD/wsdd.pdf

maybe this will get you going in the right direction...the span of the beam would seem to be influence....


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## GBrackins (May 7, 2012)

dacar,

do you mean up and down like a wall stud? or up and down like a floor joist?


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## KZQuixote (May 7, 2012)

Gary,

The latter.


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## GBrackins (May 7, 2012)

KZ,

thanks, I missed that the first time. I'll have to check that out, never seen it done that way


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## rogerpa (May 8, 2012)

Uniform load bearing capacity of a rectangular beam varies with the cube of the height of the beam. In your example (2 x 4) the "beam" would carry 8 times more load when the vertical dimension is 4 than when the vertical dimension is 2. If you increase the beam to a 2 x 6, the beam could carry 27 times more load if the vertical dimension is 6 as opposed to when the vertical dimension is 2. A 2 x 8, 64 times; A 2 x 10, 125 times; A 2 x 12, 216 times. This only works for solid rectangles.


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## DRP (May 8, 2012)

Roger gives an excellent description of moment (bending) capacity for a beam. But, I think the question is about bearing capacity of wood (compressive strength in the radial or transverse direction to the grain). If I'm understanding the op right the compressive strength perpendicular to grain is considered to be the same per square inch whether the lumber is up on its side or flat on its' face. The compressive strength is a good bit higher parallel to grain, longitudinally, standing on end. Remember that in any given board we have no control over which face is radial and which is tangential , or somewhere in between. The saw made that choice.

Then there are the real world ceaveats. Short chunks of end grain cutoffs jammed under a beam will shear. split and crumble under load. A tall narrow piece of wood under a beam is likely to tip over. Bearing on the end grain, say of a stud or post provides great bearing strength as far as the stud is concerned but it is supporting the side grain of the beam, check the bearing capacity of it perp to load.

Going all the way back behind the NDS to the USFPL's "Wood Engineering Handbook" is this comment, talking about loading perp to grain;

Stresses perpendicular to the fiber (grain) direction may be at any angle from 0 degrees (tangential) to 90 degrees (radial) to the growth rings. Perp to grain properties depend somewhat upon orientation of annual growth rings with respect to the direction of stress. Compression perp to grain values are derived from tests in which the load is applied parallel to the growth rings (tangential direction). Proportional limit in compression increases from 0 degrees (T) to 90 degrees ®, the total increase amounting to about one third. For some softwoods in compression the values at ) and 90 are about the same, with the value at 45 about 2/3 of the others.


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## peach (May 12, 2012)

if what you are describing is chunks of 2x material some of which is parallel to the strength axis and some is perpendicular to the strength axis, it's a composite situation and you need to analyze the entire system; why can't they just support the beam like everyone else does (full width, full depth dimensional lumber oriented in strength direction (generally the little dimension horizontal).


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