Engineering questions - steel laminate beams

[Billrog]

Any kind of T&G decking will add to the rigidity the most critical thing for strength regardless of what is used for joist is that their kept vertical with proper bracing. Steel I beams also require the proper stamp to meet the span and load specs. I like using them because I can buy them for 1/2 the price of engineered wood or wood product beams & they don't come with a 2 or 3" built in cant. I've built a no. of beams up to 28' with 2x 10's and plywood in between none have ever sagged after over 30 yrs. Some times were restricted to building codes regardless.

 

[Rustyiron]

WCD 5 - Heavy Timber Construction
Not exactly what you need but it might be helpfull.

 

[Jim Timber]

they don't come with a 2 or 3" built in cant.

The cant I'm talking about is the technical term for the log when it's been squared off on the mill.

 

[dstig1]

Doing a composite beam with wood and steel is possible, but you aren't thinking about it in the most effective way. I went through this exercise a number of years ago. I'm an engineer, but one of my good friends is a structural engineer that deals in this stuff. So i know what he's talking about, and it makes perfect sense, it's just not directly in my background. With that said: you don't want the steel stacked up vertically between 2x12's. You want it on the flat, above and below the 2x12's. People often have a misconception of how an I-beam works. It isn't the vertical web that gives it the real power - it is the 2 flanges set wide apart. If you add steel - well secured with many screws or bolts to the top and bottom, it will behave much more like an I-beam. The real big weakness of wood in structural applications is compression. Wood will generally fail in compression much sooner than it will in tension, so playing into that, you can gain a lot with some properly positioned steel in a composite beam to improve the compressive strength.

Other thoughts... When I designed my house, I had long span issues too. Spanning 28' free was the longest section. In the floor, I did it with I-beams as they were the most cost effective. For the main roof span, I used a Glulam, as they look nice when finished, and they will engineer and build them to whatever you need. I understand your desire to use what is on site, but this may be a case where you want to spend the money for something like that. I called it The Big Beam, and it runs 28' total and about 2' tall. Here is a shot of it finished (below). No clue what the actual cost was, but it was between $1-2k. This was from Structural Wood Products in White Bear Lake. They will deal with individuals, but it isn't their favorite thing to do. Give them a call. They can at give you some general bearings on what you might be looking at, which will give you more data to think about. Even at this stage of your project it would be worth a call after the backlog from holiday vacations clears out in a few days. They are getting into the busy season getting ready for Spring construction starts, so I wouldn't wait too long.

Good luck with your project, and feel free to PM me, if you think I can help.
-Dave

 

[Jim Timber]

I appreciate that generous offer!

If the engineering says it ain't happening, then I'll concede defeat and go with a steel beam and hide it. At least with that, I have proven tools to work with for determining load and deflection. I still need to get some books on timber framing so I can make sure the rest of my structure is sound. I've been a fan of the style for several years, but haven't worried about learning the in's-out's so much since the prospects seemed so distant. Now it looks very good that I'll be working towards getting started this spring and the ambush on my gray matter has hit full swing.

This one's not like when I built my shop. I went to the pro desk and said "this is what I want" and they plugged it all into their system and spit out a set of prints. I took those prints to the city and they charged me a fortune to mark where my sill plate anchors needed to be, and specified I needed sheer wall construction because my doors were so close to the corners (it was like $750 for the plan review), $1100 later I had a building permit. 7 days after that I had a slab, and 28 days from that I was putting up my walls. It's been 8.5 years and that building has done very well but it's in the wrong spot, and it's too small. Now I want to raise the bar.

 

[PILOON]

Once did a major renovation that called for a 30' 12" steel I beam to span an open area with wood joists to go to an outside wall.
Owners did not wish to see that steel beam so I had to be hidden in the floor.
Wood 12" 'I' joists spanned from the steel to that outside wall and were 12" apart. (joists were 2 x 3's top and bottom with ply webbing.)
The fun started as to how to attach the trusses to the Steel beam and at the outer wall which was old 2 x 4 construction.

We stuffed the steel I beam with 2 x 12 wood and used special joist hangers and at the outside 2 x 4 wall we doubled up with 2 x 6's and headed with 2 x 12's and used joist hangers again.

That was one crazy and costly renovation project that really should have been a teardown but due to many factors such as waterfront, bylaws and acquired rights, just had to be.
Existing structure was 2 ft from one side line, backed to a cliff and closer to the waterfront than newer setbacks permitted.
Teardown was no no as under renovation rules more than 50% of the structure had to be retained.
In fact we practically rebuilt from the inside out always retaining the outside cladding.
To make matters worst no heavy equipment could get near and everything needed to be hand carried including that steel I beam.
Scaffolding all had to be made up with wood with many setups canter-levered thru window openings.

Basic structure ended up 3 stories high tucked into a cliff with main entrance on the 2nd floor.

Fortunately no safety inspectors visited our site while working as for sure there could have been issues from time to time. The only incident was one worker while walking backwards on the ground, tripped and landed his butt on a cement post.

 

[Jim Timber]

I was a little shocked when I asked about my building permit at the new property and they said there were no inspections. I was instantly relieved in that I could do pretty much whatever I wanted, but then the fact that no one was inspecting people who weren't interested in the buildings outliving their entire family (like I am) scared the crap out of me at the same instant. We have inspections for the electrical (the state requires that), and plumbing if you want a CoO (needed for insurance underwriters anyway), and the site needs to be approved for avoidance of wetlands and proper setbacks - other than that, you're on your own! :cool2:

That new found liberation of not spending 3 weeks arguing with the building officials about why my 840sf building couldn't share a common wall with my existing house unless it was reduced to 460sf (I left out that part of the story in the previous post) was a big sigh of relief. We're also limited to 10,000sf on a single building without an exemption. :confused2:, and 35' tall within 900' of the lake. My house site is about 1000' from the lake, and that's a good thing because I'm hoping to do a 3rd story tower level tall enough to see over the trees (there's a hill, so we don't need to go up 70' to do it :laughing: ) and view the sunsets on the horizon.

Likewise, since no one's going to be checking my prints, I'm going to rely on other people's math to make sure what I conjure up is sound. I'll do the calcs myself too, but if I do something that's not normally done, those designs will be double checked.

My wife and in-laws went through what should've been a tear-down on their cabin because of setbacks and grandfathering. What they ended up with is a cluster-eff because their contractor was (and remains to this day) incompetent. It happened a few years before I entered the picture, so the damage was done when I learned of it. That doesn't keep me from shaking my head every time I have to reach around an open door to hit a light switch because they couldn't bother to run wiring in two separate walls. Or how the crawlspace access (where the water softener is) is dead center under the middle of a 12x28' 3' tall deck (which was on the prints from day one). There's all kinds of little flaws in that cabin like that, and the glaring one where he used 3 season porch doors on the lake and predominant wind side of the outside wall - so we have water coming in behind a threshold with a vertical weatherseal surface on the outside towards the weather. :thumbdown: I'm near certain there's rot in the floor under those doors and they're not even 14 years old.

Anyway... Back to stuff we can benefit from:

Here's the episode with the I-beam and how they did it.

 

[dstig1]

Well I got news for you - the inspectors do very little checking. Probably if you are in St Paul or Mpls they go nuts (mostly as they are looking for ways to screw you), but outside that, they sure don't seem to. When I built my shop (first part of the project) the inspector showed up for rebar inspection. He said "where's the rebar at the top of the slab?" I said this is exactly the plan I submitted, and you approved. He then spent a few minutes on the phone with his assistant trying to sort that out. Of course I was right, but I said, we can easily add that at this point - would you like me to? So we did for a couple hundred bucks. I talked with the concrete guys and they said it was a good idea, so why not? No need to fight over a good idea. But then this is something that should have been caught on "plan inspection" right? It was pretty clear that "plan inspection" mostly amounted to verifying the check cleared and checking off anything the state would come down on him for. There were a couple other incidents that verified this. I question the need for these people with this level of effort. You want to do real work, then we'll talk. If you are looking for free money, then I have another attitude about it...

Per your timber frame... Go to the Mpls home show coming up in Feb/March at the convention center. There are one or two timber framers there. I bet discussions with them would give you a very good idea of what you can/cannot do. I have found a coupe of them to be very helpful. We did not go with timber frame in the end, but it was a big part of the research.

 

[Jim Timber]

I had two people in Fridley I had to deal with - one is a moron and the other was the building official (we became and remain friends from my shop project and the discussions leading up to it). The official was (still is) constantly worried the inspector under him was going to get him fired for making bad calls. In fact, the underling shut me down for 2.5 hours the day my second two walls were to be raised because one of the (two) neighbors who had issue with my shop's construction had called complaining that my walls were already over the top of my house and the trusses weren't even up yet (which was patently false). Since my roof lines didn't match by a foot (not a code requirement for accessory structures), they did have the city planner come out with the interns they had for the summer and see if my building would meet the code (I was 3.5" too tall, but didn't know it until the energy trusses went up - they didn't use energy trusses when I had the plans printed and no one caught it). So after they said I was kosher when I told them the siding, trim, and even roof style was going to match the house, but the facia boards and gutters would be off a foot; I was back in action getting ready for the wall raising party. I found out the roof peak lines didn't meet when I had all my trusses up and was curious if my math was really that good. When I shot the laser off and it didn't hit I was puzzled - that's when I found out the bottom chord on energy trusses are thicker (for the insulation) than the standard ones they used on my prints. No one at the city's ever been told about that one, and it really was a goof. I happen to appreciate my 11'3" ceiling height though, since it gives me space for my 15" I-beam on the bridge beam of my crane and an 8' hook height under it.

I'm not building down here again. I'm building in Crow Wing county about 15 miles SE of Brainerd. I've already dealt with the wetlands issues, I know all about the RLZ stipulations, and the whole kit-n-caboodle. I'll be well outside anything that could hinder my wildest dreams besides my wallet and the tax implications of having too cool of stuff on the property. :laughing: The shop will look like a monitor barn outside. Nothing too fancy. Inside it'll have 5/8" sheetrock for fire protection and a goodly amount of insulation - just like the one down here in the metro.

 

[EddieWalker]

I just had another thought after reading your posts about wanting to make the upstairs area a living area. I walked away from a job recently where somebody cut out 4 floor joists on an old house 60 years ago for drain lines on a 18 foot span. They are all 2x12's that go about half way, then there is no more then two inches of wood left where they where cut. Oddly, the sag isn't very much and if it wasn't for a leaking toilet upstairs, probably would have gone on like that forever.

What I figure happened is the wall upstairs acted as a truss. It's right off to where they cut everything out of the floor, and it has solid ship lap on both sides of it. That wall is so stiff that it's holding up the floor below it!!!

Is there a way that you could engineer your walls upstairs to act as trusses to hold up your flooring?