Wall head detail

[MIStructE_IRE]

I have a 3 storey RC frame, flat slab on columns, with infill masonry partition walls. The walls are non load bearing. The frame will be completed first and then the walls built within.

The architect wants the top of the walls grouted tight to the slab for fire/sound proofing reasons.

On one hand, my view is that these walls are non load bearing and should have a deflection head. On the other hand, I’m thinking even if they were grouted tight to underside of slab, the relative stiffness of everything kicks in and the structure still works as designed anyway. All dead load deflection will have taken place by the time the walls are built.

I can’t say I’m overly concerned either way.. Should I be?! As usual, the preferred structural detail will be met with great resistance!

 

[EZBuilding]

In my areas of practice, it is common practice for the exterior non-load bearing masonry walls to be placed after the slab has been placed and shoring has been dropped. Sleeves in the slabs are placed to allow for reinforcement and grouting of the masonry walls below. This is often provided at interior partition walls as well.

I agree that there could be some live load and superimposed dead load transfers to these masonry walls - but it is not something that has proven to be an issue. In consideration of the fire, sound and waterproofing concerns of an alternate detail - it seems like it's the holistically preferred choice.

 

[driftLimiter]

Don't want to overload that masonry in anyway because you know the Arch will come back squaking.

I don't know your layout, but I am imagining a scenario where high stiffness of the wall causes some discontinuity in your system and might be a source for cracks to start. Sure after the cracks relax then you have the load paths you designed for but those infill walls might get punished.

Also displacement compatibility with the frame for lateral loads, I don't think this top of wall detail effects it much but it could change the dynamic behavior of your building.

 

[GC_Hopi]

Masonry infill walls are starting to get a lot more attention in the code, TMS 402 now has Appendix B, “Design of Masonry Infill”. Take a look at these references. Link Link

 

[Retrograde]

Hilti make a fire resistant acoustic mastic sealant that could be used (CP 606). Other suppliers have similar products.

 

[dik]

If no gap, you might want to add a little -ve reinforcing in the middle stip area because there will be a -ve moment developed. Plain concrete may do the trick.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[mgmc]

Leave it down 25mm or so and fill gap with mineral wool, this ticks thermal and acoustics. If its fire resistant (infill walls usually are not unless you have an inset balcony or right up close to a boundary line) you can just put in a steel angle to the inside or rely on the mineral wool entirely if you can find a product with the testing.

Why masonry though.. SFS I would think is far easier/cheaper in this day and age, at least in the UK.

 

[rowingengineer]

What about horizontal load, will this be an issue? Most of the issues I have seen have been the walls acting as poxy shear walls until something goes wrong.