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Wood Frame Shear Wall Hold Down at Masonry Wall
4

Wood Frame Shear Wall Hold Down at Masonry Wall

Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
I've got some wood shear walls coming down on parallel masonry basement walls. I have the following questions:

1) What are some good tie-down connector options for this scenario?

2) Is there anything unusual to be worried about with masonry? I kinda have this picture in my head of the tie down yanking the upper courses of the block away from the rest.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Quote (KootK)

1) What are some good tie-down connector options for this scenario?
I think the connector itself would be no different than a concrete wall. I.E. simpson strong-tie hold-downs with a anchor bolt. Alternatively you could just design a bent plate situation.

Quote (KootK)

2) Is there anything unusual to be worried about with masonry? I kinda have this picture in my head of the tie down yanking the upper courses of the block away from the rest.
Existing masonry or new? If existing then your concern would be definitely justified. If new, then grout and reinforce the cores with the hold-down anchors, and perhaps one each side of that one. A long anchor bolt would slso help, the issue would be room in the core. You could thread the top of the reinforcing i guess and use that as your anchor bolt.

But that's just me spit-balling.

Option: Blocking the chord out to match the wall width, and then long coil straps with concrete screws into the masonry wall. Likely a bit messy but it has the advantage of grabbing multiple courses of blocks.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

I would opt for a tie beam at the top of the masonry wall. This would allow for the connection to occur to a uniform concrete beam and you don't have to get fancy coordinating attachments to filled masonry cells. Hooked masonry dowels into the tie beam should allow for development of the tension, and shear loads into the reinforced masonry wall.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
Thanks for your help jayrod.

Quote (jayrod)

I think the connector itself would be no different than a concrete wall.

I guess that my main concern was the presence of the face shells. The face shells would mean that some of the embed solutions would be infeasible. Although, I suppose that there really isn't much difference in an anchor bolt scenario so long as one takes account of the material properties and proximity to edges etc.

Quote (jayrod)

Existing masonry or new? If existing then your concern would be definitely justified.

It's new but my odds of getting anything fancy done are pretty remote. I misspoke with regard to the basement wall. It's more accurately masonry grade beams.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)

Quote (EZ)

I would opt for a tie beam at the top of the masonry wall.

You mean an all concrete grade beam as opposed to a masonry bond beam, right? I'd love that but I won't be able to negotiate it here.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

I think that would then lend itself to my alternative option possibly being feasible, if you can negotiate wood wall thickness above.

What kind of masonry grade beam thickness are we talking? 8" or 10" blocks?

What's the size of the wall above? would there be any openness to matching the beam thickness?

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
It'll be 8" block and six inch studs. Little openness to changing those things I'm afraid.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

How much tension load?

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

If this is all new construction, how deep can you go with your anchor rod?

Can your anchor rod splice to a footing dowel?

How deep is you masonry "grade beam" - I don't know that I've ever seen a "masonry" grade beam.

Is there a concrete footing?

Do you have a detail? You usually do!

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Quote (KootK)

Little openness to changing those things I'm afraid.
Naturally, I'm really hoping someone chimes in with a grand solution. I've got a real outside the box type solution I can sketch up for you if you provide me with the cross section details.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Is the masonry wall fully grouted? Thankfully, fully grouted walls are extremely common in my area. We would cast in typical anchor bolt or use side-mounted steel strap (Simpson Strong-Tie makes a few)

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Could you hook the tie down into the bottom course of masonry, and have the bottom course of the masonry be a bond beam? This could help engage more of the grade beam than just the core the tie down passes through.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)

Quote (jayrod12)

I've got a real outside the box type solution I can sketch up for you if you provide me with the cross section details.

Like I'd say no to that. Hit me. Detail below. Outside of stud = outside of block.

Quote (jd)

Is the masonry wall fully grouted?

It can be.

Quote (jd)

use side-mounted steel strap (Simpson Strong-Tie makes a few)

Side mounted as in attached to the side of the block rather than embedded into it?



Quote (Shotzie)

Could you hook the tie down into the bottom course of masonry, and have the bottom course of the masonry be a bond beam? This could help engage more of the grade beam than just the core the tie down passes through.

I could. I'll just make the whole darn thing a bond beam.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Is that adequate roll-over blocking for that floor truss... wait... am I in the wrong post?

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Yes, the side mounted strap would be installed on the face of the masonry. This can only work if the masonry has finish installed over it so the strap and screws are not exposed to the weather. MSTAM OR MSTCM straps are both rated for install with titen screws into the face of the masonry. This would require the cells to be grouted obviously.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Less abstract detailing than I originally thought but look at this



Also, check out the PB holddown from Simpson Strong-tie, might be exactly what you're looking for in a sense.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)

Quote (XR250)

How much tension load?

Don't quite know yet. Relatively small. I was hoping to get a handle on the detail and a rough capacity and then work backwards from there to determine how many panels I want.

Quote (BVSD)

Is that adequate roll-over blocking for that floor truss... wait... am I in the wrong post?

LOL. As long as they actually sheath between the sill plate and wall bottom plate.

Quote (jayrod)

Less abstract detailing than I originally thought but look at this

Thanks so much. My only concern is what jd mentioned: do the straps need to stay inside of the building envelope?

Quote (jayrod)

Also, check out the PB holddown from Simpson Strong-tie, might be exactly what you're looking for in a sense.

My chords are going to land nicely upon trusses. I wonder if I could use a similar approach to tie down the trusses.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Are they not finishing the outside of the gradebeam with some form of insulation/parging etc?

If this for warm or cold climate? If cold, I assume they'd be doing something to slow the heat loss through the masonry. Insulated floors never work as intended, you really should be heating the crawlspace.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
You may in fact be right jayrod. I'll check on that.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

The straps do not need to stay inside of the building envelope, but will need to be covered with concrete or some other material to prevent ground contact. If you would feel better structurally, use one strap on each side of the wall with thru bolts - MSTI 60's or similar with the bolt holes filled. Less chance of the block face to spall out.

I would restrict the concrete strength to 2000 psi unless you can specify better...

Mike McCann, PE, SE (WA)


RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Quote (Kootk)

Don't quite know yet. Relatively small. I was hoping to get a handle on the detail and a rough capacity and then work backwards from there to determine how many panels I want.

I have been running into this monthly on my residential jobs now that they are cracking down on lateral stability in our area. Also, 75% of our foundations are 8" CMU.
As has been suggested, I run the rod all the way into the footing. I give them the option of not grouting the cells that contain the rod. This gives them some flexibility in the rod while framing. I usually show a double band in the area of the shearwall so the chord compression loads can easily span over the un-grouted cell column.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
Thanks for all the help gentlemen.

Quote (jayrod)

Are they not finishing the outside of the gradebeam with some form of insulation/parging etc?

Yes, yes they are.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
@BVSD: I apologize. In the flurry of responses, I missed on of yours and failed to answer a few of your questions.

Quote (BVSD)

Can your anchor rod splice to a footing dowel?

Probably. Currently, I'm digging XR's idea of running the anchor rod all the way down.

Quote (BVSD)

How deep is you masonry "grade beam" - I don't know that I've ever seen a "masonry" grade beam.

Poor terminology on my part. Let's call it a stem wall.

Quote (BVSD)

Is there a concrete footing?

There is. 16"W X 12"H

Quote (BVSD)

Do you have a detail? You usually do!

Yeah, I'm a sketch-a-holic. It's funny. I seem to have oodles of time to post sketches in other peoples threads. Then, when it's my thread, I'm in a hurry for an answer and I just go bare bones. I posted a partial above. If you feel that anything is missing from your mental picture, let me know.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Kootk,

One thing worth noting. if you bring your threaded rod into the stem wall and through the top grade beam so you are transferring tension loads into the rebar... make sure you put 90-degree bent bars from the vertical cells into the bond beam. try to only use one bar per cell this way at the laps you only have 2 bar diameters. I've done this numerous times and it works... as far as numbers and construct ability but only for residential so i have never inspected it during construction, TBD.

If you are using straps, you also should consider this. it will keep the bond beam from pulling off due to inadequate laps.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)
Thanks for the tip Eric. I'm gearing up to do a lot of these so coming up with a good preferred detail is key. The design of the foundation is actually not within my scope which makes things a bit awkward. I'm going to be detailing the tar out the stem wall locally but then handing off the design to someone else. Ah well...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Oh lord. Delegated foundation design? Are you designing "mobile" structures?

You could just give them the expected tensile load at each location and let them figure it out. Show an intended connection but otherwise stay hands off and cover the details in CYA statements about coordinating connection details. Is this project north or south of the 49?

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

(OP)

Quote (jayrod12)

Oh lord. Delegated foundation design? Are you designing "mobile" structures?

Close. Pre-fab.

Quote (jayrod12)

Is this project north or south of the 49?

South.

Quote (jayrod12)

You could just give them the expected tensile load at each location and let them figure it out.

Honestly, I'm not sure that there really will be great competence at that end. If I ask them to figure it out, I suspect that they'll either screw it up or just come back and ask me to figure it out later.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wood Frame Shear Wall Hold Down at Masonry Wall

Understood. And south of the border you want to tread carefully in terms of letting someone else figure it out anyway. Much better to over detail down there. We're a touch spoiled up here that's for sure.

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