Bonding steel plate to concrete

[hokie66]

Would be interested in advice on adhesive bonding of steel to concrete without any clamping force. The steel plate will be loaded in direct shear parallel to the concrete face. Some epoxy suppliers list values for bond strength, but I don't know exactly what they mean, or what factors should be applied to this stress. What would fail first, the concrete?

 

[40818]

I would be worried if i had to rely on a bond between the plate and the concrete. I would suppose the outcome would depend on the loading magnitude, but i would have thought the make-up of the concrete wouldn't give the best surface for a decent adhesive bond.

The bond strength is the allowable value for the bond itself. Think of it in 3 separate pieces, the steel conncectedto the goo connected to the concrete. The bond strenght is the allowable of the bond to transfer the load across itself. If your applied load is greater than the quoted allowable then you have a problem. But i would have thought you might struggle anyway, and if you intend to use adhesive, i would contact specialist suppliers as your use seems a bit leftfield of the norm.
I'm aero so i might be uninformed though....

 

[corrosionman]

hokie66
After 35 years experience of adhesives I,d run 100 miles before relying on a bond between steel plate and concrete, but tell us more of the intended application and maybe I will comment less adversely.
Regards CM

 

[hokie66]

CM,

I am not intending to use this solution, but just looking for any arguments I can use against it. In fact, not my job, but have been asked to comment on it.

I think 100 miles is about the right distance.

The application proposed is essentially to bond plate reinforcing to the surface of concrete elements which have inadequate strength.

 

[bridgebuster]

There are fiber wraps that can be used to provide additional strength for concrete members. One manufacturer is R J Watson. If you go this route, the concrete has to be in good condition - no spalls, scalling, delaminations etc.

I've seen epoxy and stainless steel shims used successfully as a filler material on deteriorated steel girders, to provide a level bearing surface between two steel members.

I agree with the others about not relying on bond strength. Let's assume the steel plate can be bonded; it would only carry live load and any newly placed superimposed dead load unless the member is relieved of all dead load prior to installation of the plates.

 

[stanweld]

Adhesive bonds are quite weak under shear loads and are normally not recommended for this service. Adhesive bond strength is usually cited as tensile strength.

 

[corrosionman]

hockie66
Every year Edinburg University organise a Conference on Repair and Strengthening of Structures using Resins and Carbon Fibre, Etc.
There is plenty Experience in this field - lots of Technical Papers are presented - - Instead of a steel plate, a CF Patch will have great strength but some flexibility so that the only forces on the patch are direct shear. I attended this Conference a couple of times - - but nobody yet produced any real information on the important matter of long time shear strength tests, and the difference between results from the research lab and results from the real world, out on site, possibly in winter. Maybe this is an option for you to consider.
Regards CM

 

[Dinosaur]

My argument against this sort of application of an adhesive to steel plate would include the following:

Do we know it will perform in wet weather?

Do we know that temperature extremes, such as 0 deg F to 120 deg F, will not cause a loss of strength/ductility?

Do we know that the materials expand and contract together. If not, can we predict the stress due to temperature changes? Will that exceed our comfort levels?

Is this a ductile material? Will there be noticable displacement before failure to redistribute load and provide warning?

Will this adhesive last the expected life of the structure?

Good Luck!

 

[civilperson]

Use 60 psi for bonding strength for smooth steel bonded to exposed aggregate, (cleaned of laitance and dust), concrete in both shear and in tension. Divide by some Factor of Safety that lets you sleep at night and then use Hilti RE500 Epoxy Adhesive anchor for a cost savings compared to only adhesive.