Hi.. take a look at this doc: http://www.countryplans.com/builtupbeam.html
see where the individual members have joints? Do these joint locations need to be centered over a pier, or can they be placed in between piers?
Thanks...
Frank
At first glance I would say yes but as I studied it more there is a solid member in the center. With the bonding of the plywood, outside members to the solid(non-spliced) 2X I would say no. Often a splice is situated over a supports but that is usually where there is not multiple layers as detailed in the link. An example is rim joist on a deck or porch.
Since you are building this from scratch, you can pretty easily engineer it to center most of the joints over piers.
That's what we did, and I feel pretty good about it.
We carefully measured the distance between each of the piers. Then, while in Mesa, we pre-cut the boards such that the joints would be seperated by at least 4 feet for the 2x8s and the 1/2" plywood joints were at least 2 feet from any of the other joints. In addition, we made almost all of the 2x8 joints rest on top of a pier. That wasn't possible in one case, but I think it probably doesn't matter.
Frank, it would be ideal if the joints were to fall over a pier/post. However that's not always possible. As long as each 2X joint is no closer than 48" to any other 2X joint in any adjacent layer you'll be okay.
My planned girders are made from a variety of lengths, mostly standard lengths. In a couple of spots I've designed them to have a one foot cutoff as waste. That way all my joints fall over planned post positions.