Need some assistance with an I-Beam

[LS1MonteSS]

Hello from Alabama,

I'm building my own 30'X48' Garage (Man Cave as the wife puts it)..
I'm doing mine using the post and beam construction method. Post being 6x6 (actual size being 5.5X5.5). Beams being 6x8 (5.5x7.25). Post will be spaced 12' O.C. along the 48' length for a total 10 post. Each post will rest on a 12"x12"x 14" tall concrete pier and those will rest on footers that are 2'x2'x9.250". Of course they will have the usual rebar reinforcement added to them..

I want to add a second floor to this garage.. Using I-beams seems to be the most economical way to go considering the projected span of 28'-6.5" and I will need 3 for my garage. The beams will be supported by brackets off the 6x6 post and use an additional 2"x2"x.250" haunch brace on each end that is 54" long. Could probably be shorter..
I wanted to keep the beam to a max height of 18" and still maintain a beam to floor height of 10' of clearance.
Before I added the haunch braces into the design I had figured I would need a W18X50 that had a calculated deflection of .15" for a span of 29' with a center point load of 4000lbs. My next choice (staying in the 18" or less height range) was a W16x50 with a calculated deflection of .17" for a span of 29' with a center point load of 4000lbs. Both beams had the least deflection for the 29' span.
The haunch bracing is tied to the beam 3' away from the post and the other end of the haunch brace ties back into the post 2'-9" below the beam.

I don't know how to add the haunch bracing placement into the design so I can see how it effects the over all weight bearing of the beam. But I do know that adding the haunch bracing has an effect that aids in narrowing the unsupported span. Almost like adding a post under the beam which helps aid the weight bearing capability of the beam.. This could in turn narrow the height of beam I need to carry the second floor load.

I know I will get hammered with comments like, "Go see an engineer!".. but I thought I would ask all the same.

Thx,

Kevin
Retired Army Construction Engineer

 

[DekeT]

I'll start with questions. Why are you using a point load for calculating your beams instead of distributed loading? Or did you already figure the beam for per foot loading and then just add the point load later?

 

[Architorture]

I have an approximately 28' span in my basement with 18" wide flanges...they are spaced much more closely than 12'.

when you start to approach 30' in span with a live load being supported the biggest issue is maintaining stiffness in the structure so it doesn't get all bouncy when you are walking around. The bare minimum will result in a bouncy structure.

I used to work in a very economically built office building with 30x30 bays...I sat just about in the middle of a bay and could tell who was walking down the aisle between the cubicles based upon their gait which I could easily feel transmitted through the floor

I would outright discount the W16 and carefully consider the W18s depending on the loading you are expecting.

 

[carcajou]

First of all my shop is 30x50, similar to your project. You need more posts than that if they are going to support the load of the I beams too. I would go 8" oc max. esp with the 2nd floor, likely 6' oc.
I used a 14" I beam on 6x6 steel posts, same span in my shop for an overhead hoist. There is no way 3 of these beams would support a 2nd floor without deflection. Also if you plan on a overhead door in the end(s) this also will require extra bracing.
This is from actual experience, i will leave the engineering to those that know the math.

 

[LS1MonteSS]

DekeT,
I have figured the loading both ways so I could see the deflection with the beam loaded both ways. The data for the distributed loading is as follows:
W16x50; load distributed (ppf) 480, calculated deflection (inches) .4 (13/32)
W18x50; load distributed (ppf) 480, calculated deflection (inches) .33 (21/64)

If there is some other information you need just let me know. I created a spread sheet while I was doing all this to assist in narrowing down my choices..

 

[LS1MonteSS]

First of all my shop is 30x50, similar to your project. You need more posts than that if they are going to support the load of the I beams too. I would go 8" oc max. esp with the 2nd floor, likely 6' oc.
I used a 14" I beam on 6x6 steel posts, same span in my shop for an overhead hoist. There is no way 3 of these beams would support a 2nd floor without deflection. Also if you plan on a overhead door in the end(s) this also will require extra bracing.
This is from actual experience, i will leave the engineering to those that know the math.

carcajou,

Thx for the reply.. I'm thinking your shop only has garage doors on the ends and not along the 50' length. I had considered narrowing the space between the beams but that starts to limiting your garage door options or the space you have between each door. I need 3 (9x8) doors for my project.

Everything has deflection, what is acceptable is the question.
Using 2x10 floor joist spaced 16" O.C.. I could stretch the spacing to 24" O.C. but the floor would have a little more deflection unless I use two layers of 3/4" decking. 2x10's 16"O.C. can easily span the 12'. back that with glued and screwed 3/4" decking should make for a strong floor.

 

[LS1MonteSS]

I have an approximately 28' span in my basement with 18" wide flanges...they are spaced much more closely than 12'.

when you start to approach 30' in span with a live load being supported the biggest issue is maintaining stiffness in the structure so it doesn't get all bouncy when you are walking around. The bare minimum will result in a bouncy structure.

I used to work in a very economically built office building with 30x30 bays...I sat just about in the middle of a bay and could tell who was walking down the aisle between the cubicles based upon their gait which I could easily feel transmitted through the floor

I would outright discount the W16 and carefully consider the W18s depending on the loading you are expecting.

Thx for the reply Architorture...
I would imagine that they spaced the beams closer together to account for the additional load of the number of work spaces above each 30x30 bay. Figure in the weight of each cubical structures which weigh more than most people think, chairs, PC systems, Printers, copy machines, filing cabinets, and add in all the people that are working over that 30x30 bay. The weight adds up quickly. Add one thing in that same space that the engineer didn't consider and like yourself you notice the effects.

 

[DekeT]

DekeT,
I have figured the loading both ways so I could see the deflection with the beam loaded both ways. The data for the distributed loading is as follows:
W16x50; load distributed (ppf) 480, calculated deflection (inches) .4 (13/32)
W18x50; load distributed (ppf) 480, calculated deflection (inches) .33 (21/64)

If there is some other information you need just let me know. I created a spread sheet while I was doing all this to assist in narrowing down my choices..

What is the split on your live and dead load weights? The deflections you calculated, if for live loads, will yield a very stiff floor.

I think you are going to run into a height problem because over the top of the beams you will need subflooring for the plywood. That's another 8 inches, but maybe I am seeing it wrong.

Personally I would skip the steel beams. You can easily span the width using high strength BCI joists (commercial made wood I-beams) on a 16-19.2 inch centers to get a L/480 deflection. No steel, less overall depth, ready for nailing plywood, insulation, knockouts for electrical.

Oops, I forgot to mention you would need sufficient lam beams between the 6x6s to carry the floor load. But this is a place to use the haunches on the wall to brace instead off into the open space. And your load carrying depth is attached to the wall and not in your open space.

I suggest going to a good lumberyard and getting some info on different kinds of building materials available on the market. I-joists, vlams, gluelams, etc.

 

[brownbagg]

are those 6x6 going be big enough

 

[carcajou]

are those 6x6 going be big enough

Not on 12' centers IMO.

 

[LS1MonteSS]

What is the split on your live and dead load weights? The deflections you calculated, if for live loads, will yield a very stiff floor.

I think you are going to run into a height problem because over the top of the beams you will need subflooring for the plywood. That's another 8 inches, but maybe I am seeing it wrong.

Personally I would skip the steel beams. You can easily span the width using high strength BCI joists (commercial made wood I-beams) on a 16-19.2 inch centers to get a L/480 deflection. No steel, less overall depth, ready for nailing plywood, insulation, knockouts for electrical.

Oops, I forgot to mention you would need sufficient lam beams between the 6x6s to carry the floor load. But this is a place to use the haunches on the wall to brace instead off into the open space. And your load carrying depth is attached to the wall and not in your open space.

I suggest going to a good lumberyard and getting some info on different kinds of building materials available on the market. I-joists, vlams, gluelams, etc.

Most of the inputs only call for applied loads like I used for "uniform load" (I used 480 which is really high and could be backed off to 100 or even 40 and still be safe) and "point" (I used 4000).
There are two allowable deflections used in the program.. L/240 (Commonly associated as a combined live+dead load) and is a constant 1.45" (> 1.37") and the other is L/360 (Commonly associated as the max. permissible live load deflection) at a constant of 0.97".

The 2x10 floor joist will be fastened to brackets welded along both sides of the beams vertical web member. With the 2x10's notched at the top so they are flush with the top flange of the beam.. Not resting on top.

LAM's always run taller for spans like this. That is why I was going with the steel beams. I also considered the I-Joist and did call on those and the person on the other end of the phone bulked when I mentioned I needed to free span 30 with both ends resting on 3.5". so the free spam would actually be 29'-5". I was promptly told 28' was about the max they could go.. I know different..

 

[LS1MonteSS]

are those 6x6 going be big enough

Still in the planning stages so that could be increased to 8x8 if needed..

 

[LS1MonteSS]

Not on 12' centers IMO.

any closer and additional beams will be needed. beams to span the door openings which in turn will be to support a beam.

If I totally did a 180 and stick framed the building additional post or built up studs or post would be needed and still some kind of beam would have to span the door openings to support the beams that would make up the second floor.

 

[DekeT]

What side(eave or gable) are you planning for your big doors?

 

[LS1MonteSS]

What side(eave or gable) are you planning for your big doors?

eave side