Wood Frame Shear Wall Hold Down at Masonry Wall 4

[KootK]

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.

 

[jayrod12]

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.

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.

 

[EZBuilding]

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.

 

[KootK]

Thanks for your help 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.

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.

 

[KootK]

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.

 

[jayrod12]

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?

 

[KootK]

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.

 

[XR250]

How much tension load?

 

[BSVBD]

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!

 

[jayrod12]

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.

 

[jdgengineer]

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)

 

[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.

 

[KootK]

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.

Is the masonry wall fully grouted?

It can be.

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?

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.

 

[BSVBD]

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

 

[jdgengineer]

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.

 

[jayrod12]

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.

 

[KootK]

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.

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.

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?

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.

 

[jayrod12]

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.

 

[KootK]

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.

 

[msquared48]

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)