Faying Surfaces 1

[Hammer335i]

I am engineering a galvanized or powder coated steel car port parking canopy product that uses a pinned frame system to support a lightweight deck. I would like each connection to be a single 1/2" thru-bolt, but my colleague is arguing that due to the lack of redundancy, he would prefer either two thru bolts (double the hardware cost and install time, relatively difficult to fabricate and install due to angles of the columns) or change to a slip-critical connection (so that in the event the connection fails, there is redundancy in that the bolt will still carry the loads).

I am in favor of the slip-critical connection, but I have no idea how to detail the faying surfaces or how to explain how to fay (?) the surfaces to the fabricator or installer.

Does anyone know where I can find information on how to prepare the surfaces for this connection? Can this be done prior to galvanization or powder coating? Do I have to strip off the protective coating if faying is done prior? If so, are we not concerned about the steel corroding in the fayed areas?

Thanks!!!!!


Paul

 

[hydtools]

I believe 'faying surfaces' only describes surfaces which come into contact in the assembled joint. Flat face to flat face, e.g.

What does faying mean to you that you are asking the question?

Ted

 

[Hammer335i]

In reading the AISC manual, I am given to understand that slip critical bolted joints have faying (fayed) surfaces and that special care must be taken to keep the surfaces rough, with mu=0.5 or so. I have read that galvanization tends to creep from these tensioned connections. Maybe I am reading too far into it, but I thought that the surfaces were to be prepared in such a way that they generate more friction.

I have no experience with them and I am looking for any information I can find on how to detail them and how to instruct the fabricators and/or installers on how to prepare them in the field.

 

[Hammer335i]

Any help would be greatly appreciated!

 

[hydtools]

I'm no Structural. However is some machines I've designed instructions were given to mask, not paint, or mechanically remove the coating on the joint surfaces that are to come together, the faying surfaces. Paint on the mating, faying surfaces would creep and allow the joint to slip.

Ted

 

[MiketheEngineer]

A pinned frame - all around? You won't have to worry about bolts - it will fall over under it's own weight??

 

[Hammer335i]

Just to clarify, I am looking for help on how to prepare the faying surfaces. Do they need to be roughed up? if so with what kind of tool? Are there any techniques that you've used to prepare them, or are they simply just not painted/coated and/or have any coatings removed?

Also, for all those out there that actually care, there is a moment connection at the foundation, so the bolts that hold the roof deck up would be pinned and the system wont fall down.

 

[flight7]

The RCSC Specification for Structural Joints has a pretty good description of faying surface preparation. Check the commentary of section 3.2.2. The spec is free at boltcouncil.org

 

[hokie66]

Here is one reference. Others can be easily found by googling. In addition to wire brushing as described, the surface can be prepared by brush blasting. Powder coated surfaces are not acceptable for slip critical bolting.

I fail to see why you need a pinned connection to be slip critical.

 

[hokie66]

Sorry, forgot the attachment.

http://www.modernsteel.com/steelinterchange_details.php?id=436

 

[Hammer335i]

Thanks for the best response with actual help! Just so you know - I did use google, but I found a lot technical data, not relevant to the actual preparation of the surfaces.