Faying Surface between Painted Galv and Painted steel

[CE520]

I am working on about 100 year truss bridge rehab. over the Erie canal in New York State.

My main concern is the faying surface between the galvanized and painted gusset plates and the painted diagonals.
The gusset plates are to be galvanized and painted with a 2 coat paint system.
The diagonal are to be blast cleaned and 3 coated painted.
I have attached the connection detail for reference. (

http://files.engineering.com/getfil...198-45a5-a5a2-654d504717c9&file=Untitled.png)

All connections are bearing connection - no connections are slip critical

Normally the faying surfaces between the two would have only been 1 coat of paint on it but the owner wants the full system (3 coats) on the faying surfaces.
I do not see the advantage in having a 3 coat system on each member. Engineering wise the only reason i can come up with that with that many layers of paint between each member would reduce the clamping force of the bolt(which does not hold much weight due to the connection being a bearing connection. Also that when the paint compress under the torque of the bolt, i fell that would increase the chance of rust at these locations.

I am looking to apply a single coat of paint on each faying surfaces. This work is to be begin 2/1/18, which if you dont know the average temperature in new york that month is about 30 F. (this work cannot wait to the spring to be painted, either)

Any help would be appreciated.

 

[SlideRuleEra]

1. ...the Owner wants the full system (3 coats) on the faying surfaces.

2. ...the only reason I can come up with that with that many layers of paint between each member would reduce the clamping force of the bolt(which does not hold much weight due to the connection being a bearing connection.

3. ...when the paint compress under the torque of the bolt, I feel that would increase the chance of rust at these locations.

1. Be careful and prepared. Is this a "sophisticated" Owner, with a qualified in-house engineering staff? There is a time and reason to resist Owner requests. IMHO, this is not one of them, discuss your concerns... but be prepared to back off, even if you continue to believe the Owner is wrong.

2. Be prepared to explain how (if it does) clamping force is reduced and how much it is reduced. Also, the consequences of reduced clamping force.

3. Speculation? Any proof from other projects?

http://www.SlideRuleEra.net

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[Once20036]

If it's not a slip critical connection, and it is a bearing type connection, why are you concerned with the clamping force of the bolt or a thousandth of an inch of paint compression?
Is this a durability question more than a structural suitability question?

 

[racookpe1978]

Do you need to "unbolt, open, expose, clean/dustblast, preserve, and rebolt" every joint?

Seems you'd be unable to reliably get to the concealed surface between every piece of steel and steel framing unless you do.

I agree, the compression of the six new paint surfaces (3 on each surface) between the two pieces of steel will create a noticeable flexing but cracking rubber-like goo between the two pieces of steel.