Wood Shear Wall on hollowcore plank.

[jocey30]

I am reviewing an apartment building. It is 3 stories with a basement.
Hollow core planks are the grade level, supporting 3 floors of load above.
The lateral system is wood shear wall (in the interior and perforated wall on the exterior), that bears on hollow-core plans (8" and 12").
The EOR has specified a line load for DL, LL and hold downs at the ends of wood shear wall to hollow core.
(1)Wouldn't he/she also need to specify a shear a load for the wind loads that are transferred?
I would think so.
(2)So the hollow core would have to be checked for shear capacity for the line shear coming from the wall above, right?
What is everyone's thoughts?

 

[msquared48]

The hollow core should not be a problem for lateral shear. The shear load transfers, as well as any uplift loads, should be specified by the EOR and details provided for attachment.

I would worry more about installing any hold downs needed that will have to be embedded in the planks and how that is going to work with the PS tendons. The tendons are usually low in the planks, so after-set or epoxy anchor bolts should be able to be installed, but some cells may need to be grouted more than normal to achieve this.

Mike McCann, PE, SE (WA)

 

[KootK]

Some additional thoughts:

1) In addition to the shear wall tie down force, the shear wall compression chord force should also be communicated for design somehow.

2) Shear ought not be a problem for topped planks themselves but, if the wall shear loads aren't shown, the shear demand a the plank / bearing connections certainly should be.

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.

 

[jocey30]

Thanks Mike and KootK

1. The shear load transfer was not specified. I would think that needs to be specified and designed for, because of the presence of hollow space. Reduced shear capacity compared to a solid slab.
2. Yes, the cores are grouted and the prestressing strand is at the bottom. The bolts do not extend all the way to the bottom. So that is not a problem.

KootK, these planks are not topped. Usually in a totally precast building, the topping takes the (diaphragm)shear. What I'm dealing with is not the diaphragm shear, it is still a plf shear from shear walls on 3 floors. I thinks it would be a simple calculation of shear capacity of concrete (8" hollowcore - hollow space) vs required. Would you agree?

 

[KootK]

I'm dealing with is not the diaphragm shear, it is still a plf shear from shear walls on 3 floors. I thinks it would be a simple calculation of shear capacity of concrete (8" hollowcore - hollow space) vs required. Would you agree?

I don't agree. Something's gone off the rails here. The shear in a shear wall that is due to wind and earthquake loads represents a horizontal plf force applied to the precast floor plate. And that force would be resisted by in-plane precast shear in the plank/topping.

The shear that you seem to be concerned with is the the vertical shear across the planks. That shear would be a function of the vertical acting gravity loads supported by planks which has been specified by the EOR.

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]

I agree with KootK on that.

Mike McCann, PE, SE (WA)