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3/4"x24" wood, allowable fb?
i am an experienced structural engineer, however, i am a novice to wood design, i do have the current nds set. i am building a home bar, and would like to check how long i can span 24"x3/4" maple or cherry wood, flat use, simply supported. how do i determine or where can i find the allowable fb, prior to multiplying by the applicable adjustment factors. i plan to use 10psf total load.
is your bar so big that you're concerned with saving a few intermediate supports?
my 1999 nds set (asd) came with a supplement for structural use panels. it has the information you're looking for, as well as examples showing all of the design checks.
if you are using it as a shelf, i would think long term deflection may control.
this is somewhat a paradox, an engineer building a bar, yet wanting to make sure it meets code.
to be honest, use some plywood substrait or mdf, and put the wood over it, it will be alot more solid.
if indeed it is a shelf, you can stretch the span by supporting along 3 sides and providing a small edge board (glued and screwed to the shelf) along the unsupported edge for stiffening.
not a shelf, just a standard 42" high, wet bar. i want to verify if it can span 6 to 7 feet without interior supports. i looked thru 1999 nds structural-use panel supplement, i didn't see anything regarding the allowable stresses, fb, for different types of wood, specifically maple or cherry.
it is unlikely that the 3/4" material you are using is stress rated material. if the material is not grade to assure that it meets a structural grade, then you will not find any design values for it. most 3/4" materila is graded for appearance not strength.
if it's a "bar" that will support drunken co-eds, something along the lines of what they do at coyote ugly, then go with a 100 psf live load. self-weight dead load.
mixed maple beams and stringers no. 1 has fb=975psi without any adjusment factors. cf=.74
6 or 7 feet sounds too far. you don't want a bouncy bar. i am thinking 2' is best, 3' most.
another table has 725 for 2" wide. i don't think these values offically apply.
nds-2001 has values for "mixed maple" and "red maple" in table 4a. allowable bending stress varies from 225 psi to 1300 psi, depending on grade.
nds takes this information directly from the "northeastern lumber manufacturer's association"; here is their download

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