Stud rails too high

[said the noob]

Hello everyone,

I had recently reviewed a slab and mentioned in my site report that the stud rails were too high and may stick out of the slab however the contractor never followed up with it and now the heads have no cover, it’s literally flush with the top of slab,

I still think the stud rails still performs it’s job but problem now is they typically sandblast and apply traffic coating,

This is where we probably need to talk to a materials consultant and get a proper product applied over the heads to prevent corrosion,

Am I correct in thinking It is still still stucturally acceptable? The studs still do their job In preventing punching shear as the studs can still develope. The top mat cover was OK at the time 40mm top cover for parking slab,


Tia

 

[KootK]

I would agree that the studs can still serve their structural function. I'd recommend giving some consideration to fire protection of the studs however. This may be ok as you're generally worried about protection from fire below the slab but I'd still want AHJ approval on that.

 

[KootK]

Actually, there may be some impact to structural performance. Assuming that the studs were right sized to begin with, that would mean that the bottom of the studs are now also too high, correct? In that case, your effective depth for both shear and flexure may be somewhat reduced. I don't think that most engineers would consider these impacts to be consequential. In my past dealings with the stud rail engineers, they've been pretty liberal with this kind of thing as well.

 

[said the noob]

Hi kootk the stud rails were just fabricated too tall for a different slab thickness else where, just wrong rails used.

Thanks for the reply.

 

[cliff234]

You did not ask this, but,...you said that this is a parking deck. ACI recommends that parking slabs have at least 1 1/2" of top cover over reinforcing steel, and epoxy coated reinforcing steel (depending on where the structure is located) to prevent corrosion. Your studrails have no cover, and I am guessing are not epoxy coated. The traffic bearing membrane will provide some protection, but in the long run the studrails will start to corrode. Are there floor drains near the studrails? If so, there will probably be puddles near some of the drains.

 

[KootK]

ACI recommends that parking slabs have at least 1 1/2" of top cover over reinforcing steel, and epoxy coated reinforcing steel

Could you direct me to that provision cliff? That may be useful for a little reno that I'll be doing in the new year.

 

[cliff234]

KookK,

ACI 318-11 Section 7.7.6 discusses additional cover in corrosive environments (and they actually recommend 2" cover - but we use 1 1/2" with epoxy coated reinforcing steel). ACI 362 (Guide for the Design of Durable Parking Structures), Table 3.1 also lists recommended cover for various durability zones. And for parking structures we usually specify a corrosion inhibiting admixture in the slab (DCI or similar product)

 

[said the noob]

No immediate drain near the area of concern,

We had provided 40mm to top of reinforcing for all our jobs without epoxy coating for the reinforcing,

Material engineer reviews our mix designs for parkade levels prior to construction commencing, I am almost certain there is no dci in it. Will have to check though.