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Curious as to the actual use of this memebr?

Curious as to the actual use of this memebr?

Curious as to the actual use of this memebr?

(OP)
I have had a debate with other engineers in our office about the function of this member. See attached sketch. I am talking about the red member I have labeled "splice"

Can anybody elaborate?

Thanks


RE: Curious as to the actual use of this memebr?

1st of all... 8" x 16” oak beam!! Wow.
Perhaps someone felt a need for a tension resisting connection beam to beam, if I'm understanding your drawing correctly.

RE: Curious as to the actual use of this memebr?

If the beam was designed as a continuous member, the splice would be necessary to resist the negative moment over the column.

/I also echo Triangled's comment about the seemingly excessive nature of the beam material.

RE: Curious as to the actual use of this memebr?

(OP)
It is an old industrial building with another floor above, tunred into offices and mixed use. It is three spans. Two outside walls (masonry), and two composite columns.

A few of these "splice" members are broken at the nail locations.

I am thinking that they were installed to resist longitudinal movement of the beam away from each other? Basically, to tie them together, but with little or no moment resistance.

RE: Curious as to the actual use of this memebr?

Well, they are wood splices over a steel plate at a break in the main wooden horizontal beam. OK, sort of makes sense - if you assume the steel plate needs to be supplemented by a splice across it to carry vertical loads. Certainly it will not - as pointed out above - carry moment loads.

or, it did "try" to carry moment loads at some earlier lifetime of the wooden building, and the splices failed utterly at their nailed joints.

So: Leave the splices as-is, but clean them up and get rid of the nails! They are splitting the wood beam right where the load is the most (over the steel plate at the column) and they are splitting the wood splices. Bolt through the wood splices and the wood beam and clamp the joint tightly together. Epoxy or glue it? Not sure if that will help unless you can clamp the glue and split ends all together while drying.

Is every one of the steel plates in good shape? Not bent, not rusted, not distorted or itself splitting or slipping? They are what is holding up the second floor.

RE: Curious as to the actual use of this memebr?

I hate to tell you this but as shown that (those?) 2x12's are inadequate to do much of anything other than possibly provide a bit of tension capacity, depending on how it's connected. It (they) certainly will not provide enough capacity to convert those simply-supported beams into a continuous beam.

Is this an existing condition or a proposed retrofit?

RE: Curious as to the actual use of this memebr?

(OP)
Existing condition. I consider it simply supported beam/column configuration.

I was assuming it was only there for tension purposes longitudinal to the beam.

Steel plates are in good shape. Looks to be a recent (within the last 40-50 years) renovation where the wood "keystone" was replaced with a grout/concrete one, the columns used to be wood, and cast iron plates replaced for steel.




RE: Curious as to the actual use of this memebr?

Not knowing anything else about the structure, the beam might be acting as a chord or collector element. Keystone/grout block for compression due to the beams not butting up tightly and wood 2x splice for tension along the beam line.

RE: Curious as to the actual use of this memebr?

All modern wood framing uses Simpson strap ties to tie beams together. Plus, wood shrinks a bit axially. With such massive beams, the tension force induced into the ties could be very large.

Typically, for normal wood construction (SFR), I use Simpson CS18 x 2'-6", both sides.

RE: Curious as to the actual use of this memebr?

(OP)
This is an old building where the owner was (I assume) trying to maintain the original look.

RE: Curious as to the actual use of this memebr?

From the picture, I would say the 2x12's are meerly being used to support the planks until the new keystone dried. Then just left in place rather than being removed.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

RE: Curious as to the actual use of this memebr?

(OP)
The planks were there on original build using the wooden "keystone". I will try and find an image of the original setup.

RE: Curious as to the actual use of this memebr?

If the 2 x 12's don't actually tie the beams together, what else does? Is this in a seismic region?

The "antique look" could be attained if you use specially detailed straps of at least 3/16" thickness, and paint them some color other than silver. Use lag screws rather than nails.

RE: Curious as to the actual use of this memebr?

(OP)
No, not is a seismic region.

RE: Curious as to the actual use of this memebr?

Old - that's the key. This is typical in old mill construction. I've attached a picture from a old book I have (the original bookplate says 11/1/13, 100 years ago!) called The Architect and Builder's PocketBook, and if you look hard, you can see at each beam connection over the columns, there is a strap shown.

RE: Curious as to the actual use of this memebr?

(OP)
Bingo! Exactly what we have going on here.

Is that the name of the book the image is from? The Architect and Builders Pocketbook?

Thanks

RE: Curious as to the actual use of this memebr?

yep, sure is. I bought it in a used book store in Boston about 14 years ago.

RE: Curious as to the actual use of this memebr?

I have also seen vertical round metal dowels welded to the oak beam bearing plates to act as horizontal tension/lateral constraint ties.

You might want to do a scan on the bottom of those beams from the side. If those dowels are present as I suspect, you may not have as much of a problem as you think.

Mike McCann
MMC Engineering

RE: Curious as to the actual use of this memebr?

(OP)
Thanks guys. I was just suggesting we could perform the same function if we had a steel pin or dowel.

Much appreciate all of the help.

RE: Curious as to the actual use of this memebr?

wow. nice book sita.

RE: Curious as to the actual use of this memebr?

I have a ton of those old books. They're great for figuring out the structural system in an old building, and even better because they give explanations about what the original designers were thinking. Sometimes husband gives them to me for our anniversary!

RE: Curious as to the actual use of this memebr?

This is a splice to transfer out-of-plane wall loads so that you have a continuous cross-tie.

Even the old farts new they should do this before it became a code requirement. I think the problem was they didn't design the splice for enough load!

RE: Curious as to the actual use of this memebr?

(OP)
When you say "enough load" are you referring to pure tension longitudinally along the length of the beam?

Can you elaborate on the “out-of-plane wall loads” a bit?

I was thinking it was purely to tie the beams to each other?

Thanks again for the help.

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