Thread replies: 10
Thread images: 2
Thread images: 2
File: micro-lam.jpg (73KB, 800x600px) Image search:
[Google]
73KB, 800x600px
I am building a warehouse/garage thing. The roof is 1/2" OSB over 20' 2x8s 12 OC supported by three micro-lam beams and two ledger boards consisting of doubled 2x12s carriage bolted to a masonry wall.
The micro-lam beams are three 2x12 beams put together with 5.5" nails and construction adhesive, with carriage bolts when they connect to the posts.
The longest beam is 35' and has a worrying amount of sag, when walking on the roof it is very noticeable. I have a temporary post in the middle of it, but I really want to avoid having a post in the middle of the building.
The ceiling will be ribbed steel, which will add rigidity, but not much strength.
My plan is to jack up the beam, build 36" triangular support members where the beam meets the column, and attach 15' steel plates to either side of the beam in the middle of it with some big screws. I would likely have to fabricate the plates, but I can do it. Do you think this would be sufficient to stiffen the beam?
The roof is on a 1/12 pitch and will be rubber. I am in Michigan so snow load is a concern.
TL;DR How can I stiffen an assembled mico-lam beam without using a column?
Pic-related, but not my exact building, can take pics tomorrow.
>>
>>1133178
>The roof is on a 1/12 pitch and will be rubber. I am in Michigan so snow load is a concern.
You done goofed, son.
>>
File: Untitled.png (11KB, 835x504px) Image search:
[Google]
11KB, 835x504px
>>1133187
It fronts Woodward (major road) and they restricted me to 15' frontage with a 30" parapet wall, so to keep my ceilings high that's what I did. It will drain water just fine, but snow will be there for months. I am spraying hydrocarbons into the atmosphere as we speak to keep the snow away.
>>
What kind of hurricane ties are you using? Perhaps bigger ones would help?
>>
>>1133178
Tie it to the roof truss framing above. Just did it for my dad's garage and I live in the same area as you.
Also am engineer
>>
>>1133231
There aren't any trusses. Theyre attached with hurricane ties, how else would you attach them? Scabs from the beam to the joyce?
The beam is supporting the roof structure, attaching then together more won't take any load off the beam I think..
>>
Well I built some triangular supports, might still do the steel plates as well if I can source them for not $2000
>>
>>1133239
Well quite frankly you have too long of an unbraced span which is what is causing the sag. Many times the sag is only detrimental to your concern of a failure, and not anywhere near an actual failure.
Can I have a detailed description of the sizes youre dealing with? How long is the beam what is the sizing, what are the span between the walls surrounding it. What is it entirely supporting?
>>
>>1134199
It was within the manufacturers for a micro-lam beam. Maybe glulam would have been better.
>35ft long
>composed of three 2x12 micro-lam beams
>secured together with glue, 5.5" nails, and carriage bolts at the post intersection.
>posts are 6"x6"
>the other beams are shorter, and 19' away, or a CMU wall supports the roof, also 19' away
>roof is 2x8s 12" OC and. 5" PAN
I measured the deflection of the beam, it is 1.25" at its worst over the 35' span. Microlam doesn't come with a crown like glulam, but I thought it would be ok.
>>
>>1134345
You about a half inch under the recommended "allowable deflection", so really you should be good if you don't notice anything change within a year or two.
I would be concerned about it buckling say towards the front of the garage and failing in that direction rather than from the sag if that makes sense.
Thread posts: 10
Thread images: 2
Thread images: 2