slant eyes

does anyone know if there is a structural difference between (1) 6" x 12" x 18' beam as opposed to stacking like (8) 2" x 6" x 18' pieces of doug fir?

i've called the local lumber yard and they want 183 for ordering the beam. but i can get the 2 x 6's for a little under 10 bucks x 8 = little under 80 bucks.

when i worked at the sound studios (sony studios, la center studios, culver studios, and hollywood studios), they all used stacked 2x6's and hang 1 ton motors off of them.

i was directed to the code enforcement and they were closed. i've called around friends and no one has a definitive answer.

thanks in advance

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PenguinsRock

It is a common practice to bolt beams together to make a wider beam, however you DON'T want to laminate the beams one on top of the other as most of your strength comes from the depth of the beam. I would recommend looking at bolting 1" or 2" x12" boards together to make your desired width.

Also with a large beam as you are talking about it may be more feasible to make a composite beam (laminate the board with steel plates, the board provides width for mounting other things while the steel plates supply the strength). The elastic modulus of wood is roughly 12GPa, while steel is 200GPa; meaning that a 0.5"x12"x18' steel beam would have more strength than the 8"x12"x18' beam. The equation that I used was:

Steel width (in) = (12 GPa Wood/200 GPA Steel) * Wood Width (in)

By making the wood narrower and adding steel plates the effective cross section becomes an I beam.

This is more than you probably wanted to know but I thought that I would answer to the best of my ability. You could look more into this on the net www.engnetbase.com is a good reference site.

Mark