re: load bearing angle iron load question

[gramps]

I am not an engineer, but have knowledge on the building sciences side so please be patient with me.

I have an old home that uses imbedded beams inside concrete block to support the first floor only. The basement is being insulated. I know that when you insulate the rim joists, the exterior side of the joist becomes colder, increasing condensation potential and rot. I am dealing with this situation by intentionally passively heating the joists with metal bars, which has been proven to help, but not foolproof.

What I want to do is to add angle iron under the joists which is bolted to the block wall. What this does is support the joists to the interior of the cold spot. For your interest, see page 30 in this document for a picture.

expt_mtg_mass_masonry.pdf


The joists are 2"x8" 12" O/C" spanning 13' with a 3/4" wood floor, 3/4" plywood subfloor and 3/4" cross panel floor. Due to an issue with the current subfloor and slab, i can't use metal columns underneath.

I wanted to know what size of angle iron to use to bolt against the concrete wall, and what size sleeve anchors are recommended for concrete block.

thanks for your help
-g

[Kelly_Bramble]

Several thought come to mind...

First, sealing the wood will prevent rotting due to water developed condensation.

Second, not having any information on loading requirements I would suggest any steel angle that is sufficiently large enough to accomodate the anchor bolts and the joist. Or, for simplicity larger is better...

See Structural Steel Shapes or Structural Steel Shapes #2 and Structural Shapes Menu

The anchor bolts will likely not be larger than 3/4" and I would consider a steel backing plate for bearing area.

[gramps]

I would suggest any steel angle that is sufficiently large enough to accomodate the anchor bolts and the joist. Or, for simplicity larger is better...


The anchor bolts will likely not be larger than 3/4" and I would consider a steel backing plate for bearing area.

I don't know how to read the charts you posted. I have tried to wrap my head around it, but i cant.

when you say anchor bolts are likely not larger than 3/4" do you mean thickness or length?

[Kelly_Bramble]

I don't know how to read the charts you posted. I have tried to wrap my head around it, but i cant.

when you say anchor bolts are likely not larger than 3/4" do you mean thickness or length?

I meant 3/4" diameter. The max loading of a 3/4" grade 5 bolt in single shear can be calculated:

Average Shear Equations

Shear Stress ave = F/A

Grade 5 bolt Tensile strength = 120,000 psi
Area = .3340 in^2

120,000 psi x .3340 in^2 = 40,080 lbs per bolt.

Two 3/4" bolts installed properly are good for about 80,000 lbs single shear each.

[gramps]

I meant 3/4" diameter. The max loading of a 3/4" grade 5 bolt in single shear can be calculated:

Shear Stress ave = F/A

Grade 5 bolt Tensile strength = 120,000 psi
Area = .3340 in^2

120,000 psi x .3340 in^2 = 40,080 lbs per bolt.

Two 3/4" bolts installed properly are good for about 80,000 lbs single shear each.

Okay, but at what length? and correct me if i am wrong, but concrete anchors need to be used only in concrete? I thought sleeve anchors were the best choice for block. Then again, i don't have much experience myself with concrete and fastening systems.

[Kelly_Bramble]

Okay, but at what length? and correct me if i am wrong, but concrete anchors need to be used only in concrete? I thought sleeve anchors were the best choice for block. Then again, i don't have much experience myself with concrete and fastening systems.

I think you should first pick which concrete anchor you want to use. I would consider Hilti concrete anchors. Hilti and others provide documentation on the proper installation (depth, size, grouting) for each concrete anchor size.

See: ASSET_DOC_LOC_30_APC_RAW.pdf


See pages 4 - 6 "Minimum Embedment"