16' opening Door header: on load bearing wall

[LD1]

I think I forewarned everyone that I would be asking lots of questions about my upcoming bard build.:laughing: This is just another...


I know we touched on this topic in one of the other threads, but would like to focus on JUST the header.

The building is going to be a 40x72 with 16' doors on the eave (load bearing) sides. With 8' OC posts, over the door will be omitting one post. So a 16' span, with a truss smack dab in the middle. All of the span tables and calculators I have came across all deal with distributed loads, and NOT point loads.

Further more, I am having a hard time finding any data on how much strength plywood or OSB add to a mulit-piece beam. I have up to 24" of depth to work with, as the walls will be 14' and the door only needs to be 12' high.

So I am looking for the most cost effective way to get the strength needed. From the reading I have done, several sites mention that adding plywood does NOT add as much strength as people believe.Several sources state that Using 3 2x12's with 2 ripped sections of plywood in between gets 5.5" wide (to match the post), but using an extra 2x12 would be stronger than the plywood. (and 0.5" wider too). Further they go on to say that the plywood is mainly just used to get the beam the same width as the wall.

And from further reading, the modulus of elasticity of several types of plywood all seem to be about the same as SYP lumber. (1.6 million). So that seems to confirm that.

Not really looking to go the route of layering in steel plate, cause that increases difficulty of construction. And if I was going steel, I would just size a beam and be done.

Given the building span, truss spacing, and snowload, I need a 16' header that can support 6000lbs right in the middle. (Thats 30 PSF total load plus 1000# just to be safe). I have got some ideas floating around in my head, I'll sketch them up and post. But looking for ideas as to what others with similar span and loading have in their buildings for a load bearing wall?

 

[LD1]

Here is what I am thinking right now.

option 1:



A 2x8 on top of a 2x12 joined with 1/2" plywood or OSB. Thus making a 2" wide and 18.5" deep beam. Adding a 2x12 behind it to add to lateral stability and overall strength. Doing the 2x12 behind is the reason for the 2x8 being on top...so they overlap.

The resulting 2x18.5" beam figuring the strength (Moment of inertia), using the formula (W x H^3)/12 I get an i^4 of 1055. And for the 2x12 it would be 178.

So the sum of the beam strength would be 1233

Option 2:
Using the more common method of 3 2x12's with 2 layers of plywood result in a 5" x 11.25" beam.



The relative strength of that beam would be 593. Or less than half of what the larger beam is, AND requiring more material, being heavier, and costing more. Only advantage of this is more strength in the y-axis.

Given that I have plenty of height, any reason no to use option 1? Or any better solutions that arent gonna break the bank?

 

[LD1]

Here is the bigger picture to help get a visual.



Again, I have plenty of height (depth of beam) to work with. And with a given amount of material, more strength is gain by depth than width. So my emphasis to go deeper instead of 3 or 4 plies wide to get the same end result.

Also considering adding some knee braces to further reduce the effective span of the header. But this is just for extra measures. I want a beam that the knee braces are not needed for strength, but rather a extra bonus if I decide to add them. Same with the metal siding. IT will add a bit of strength to the beam itself, but leave that be a bonus.

Final question before I wait for some responses........

With the load being right in the middle of the 16' span, how would you section the plywood? Would you use 2 8' lengths with the joint right where the load is? or would you go 4-8-4 and have an extra joint, but being farthest from the load?

 

[radioman]

ONE word .. LVL's . I would be using lvl's that is 18 ft long and get them 5 1/4 thick , i think its rated for 40 psf live load.

 

[boggen]

option 2 is what i have here one 2 buildings.

err i take that back...

two, 2x8's, with a 2x12 on the loof area (main building, then one side is extended out for a roof, use to be for cattle, to get up under for snow/rain and like. and spacing is 14' to 18'
the shed is guessing 40 plus years old. not sure if plywood was even known back then, but in either case the lumber is exposed to the elements. (rain splatter, wind/snow blowing up on it. i doubt plywood would last being outside.

as for the actual doors, they are on the "peaks" the ^ triangle ends. and one i want to say is two 2x8's, with either a 2x10 or 2x12, and the other is possibly two 2x10's, with a couple 2x6's.
both sheds have sliders. (doors slide like a sliding door many folks have on there homes), and the reason for one of the lumber being different size, is for the track.

i am not sure if i would trust plywood out here on this farm, more so over the years, due to all the mice, rats, ra-coons, cats, etc... they get in and pea and poo, then birds getting in some how and making nests.
leave door open by accident or on purpose. and a good wind and everything ends up wet.

===========
with above said, i would more trust plywood say in a home, were things are covered from the elements, and from all the little animals eating,chew, and making a mess of things if and when they do get in. or for say your trusses or like were they are out in the open. but being up next to a side, is acking for dark areas for critters and like to be crawling around.

*shrugs*, no builder by no means, just what i have seen and dealt with here on the farm over the years of what has and has not lasted.

 

[patrick_g]

Don't underestimate the utility of laminating galvanized sheet metal in layers with OSB or plywood. Plenty of through bolts, don't have to be large diameter but relatively close spaced. The idea is to keep the steel flat and when flat is very stiff. That is often done for 16 ft wide overhead door headers say when you have a garage in the side of a two story house and have to have a robust load bearing header. Concrete with ample correctly configured reinforcing steel is a another possibility. Glue lams (laminated beams) can be had in various sizes and can themselves be joined/laminated for greater strength. My 5000 sq ft plus house uses multiple glue lams as ridge beams atop the roof. My walkout basement has the walkout side mostly in glass and supporting two floors above it. The header beam above all the south side glass is steel reinforced concrete and was designed by a PE. Here we are a decade later with opening windows and sliding glass doors (6 footer) still working perfectly.

Best of luck to you however you choose to proceed.

Patrick

 

[LD1]

Trying to avoid the glue-lams or LVL's. Same with layering in steel and having to drill/ bolt etc.


The LVL or multiples required to attain the strength needed, by my figureing, would have to a pair of 16's or pair of 18" depth beams.

That puts the cost of each header ~$200

Option 1 that uses plywood contains $80 in material.

And a simple I-beam that weights ~350# would limit deflection to 1/4" with 6000# load and would cost roughly the same as the LVL's.

So dollar for dollar, I would just go with an I-beam over LVL.

But would prefer to stay with wood for cost reasons.

 

[LD1]

ONE word .. LVL's . I would be using lvl's that is 18 ft long and get them 5 1/4 thick , i think its rated for 40 psf live load.

Having a hard time finding anything that gives their strength in terms of mid-span point loads. EVERYTHING I am finding on anything wood related is in uniformly distributed loads.

And due to cost of LVL's, I would go steel first. See above post.

 

[EddieWalker]

Sometimes it's better to spend the money and get what's designed to do the job. How much do you expect to save engineering and building something yourself? How long time are you willing to put into it versus just popping a glulam up there and being done with it?

3 1/2" x 11 7/8" x 16'9" for $190 is what I'd use.

https://shop.mccoys.com/building-materials/lumber/engineered-lumber-products/laminated-beams/p.1536

Eddie

 

[ray66v]

Not understanding why there is an issue? You are not the first person to put a 16' door in the side of a pole barn.

Mine has a 16' door in the side, with a second floor above it.

I have a wood header, with a 1/2" steel flitch pate in it.

There is no perceivable deflection over the span.

I would never use anything else but steel, for a span like that. Steel is the only thing I have not seen sag.