I still dont see why you need a 6k lbs in the exact middle. The only thing that comes to my mind is you want to drive a tractor or something to the edge of the second floor right above the garage door.
Some others answered this pretty well, as did I a few posts ago. 8' OC trusses spanning 40' with 1' overhangs. Makes each truss end have to carry 6000#. For every other truss it is a non-issue, as they will be sitting on top of posts @ 8' OC as well. Except for the 16' door opening which is absent the post.
Also - we came up with current technology building techniques, but didnt know you wanted to go cheaper. usually this is the best way to have regrets instead of doing something right the first time. Believe me, I get it-its hard to spend your own money on the right materials, but easy for us to say it behind the cyber keyboard.
Not looking to go cheaper in the sense that you mean. Just not looking to overspend if it is un-needed.
I could go with 8x8 posts, 2x8 walls, and 12" thick concrete if I wanted. But the only thing I would regret would be the empty wallet.
IF, $80 of lumber is capable of doing the job just as well as a $200 LVL, steel, etc. Then why spend extra is my question.
I was guessing he was using an area of 21' long (1/2 of the 40' span of his trusses) + 1' for overhang and multiplying it by 8' wide (the spacing of his trusses). This should lead to an area that has to be supported being about 168 square feet. Again, I'm making some assumptions/guesses, but I'm figuring 5 lbs/sq. ft. for dead load (building materials) and 30 lbs/sq. ft. for snow loading for a total of 35 lbs/sq. ft. X 165 sq. ft. = 5,880 lbs total load. I think the OP's concern is that all of this load will be more or less point loaded in the center of the span.
Pretty much spot on. I was figuring 30PSF total load and adding and extra 1000 though for good measure.
Reviewing some span tables that I have, they say that a No. 2 SYP 2x12 (dressed) will support an evenly distributed load of 1,582 lbs on a 16' span. My table also notes that point loading halves the value of loading, so in this situation, the 2x12 would only be rated to support 791 lbs.
I think the pole barn has 6x6 poles, so a width of 5.5" is what the OP would like to stay at, which would be 3-2x12s with 2 pieces of 1/2" plywood or OSB sandwiched to make the 5.5" wide work out. However, I believe that the fear is that this header wouldn't be equal to the task.
If it were my barn, which it is not, I would go with 3-2x12's and sandwich plywood/osb and call it good. Most of the load tables are pretty conservative and they base it on a minimal deflection (1/240 of span on this particular table). Depending on how I was going to finish the inside of the barn, I would probably go ahead and go with 4-2x12s and let it stick out a little bit. Either way, I wouldn't lose sleep over a lack of strength in this header.
So to the OP, I think you've been given a myriad of advice, all worth exactly what you've paid for it. Good luck with whatever you choose and take care.
SO given all of that, IF it was your barn and you had 24" of height to work with for a header, you would still choose to stack them up side by side? With 4 stacked beside eachother the "total load" based on 791# each is just a tad over 3000# capacity. Or only half of what I need.
Taking a 2x12 and placing it beside the first doubles the capacity.
TAking a 2x12 and placing it UNDER the first, (thus creating a 2x24), you get 8x's the srength.
Really, a 2x12 with a 2x12 under it is enough to hold the 6000#. The 2' strip of plywood holding them together is just an added bonus. Only concern now would be the horizontal strength. A 2" thick beam over 16' dont offer much of that. But a simple 2x6 or 2x8 laid flat across the top (and/or botom) of the header should suffice.
