Grout Under Sliding Connection 1

[canwesteng]

I am thinking about grouting piers to ensure equal elevations, then using chemical anchors and a Teflon pad to achieve a sliding connection. It's not clear to me if this is something reasonable to construct. I think typically the column is placed then grouted, so somehow the pad would have to be attached to the steel at that point, unless I'm missing something. Any suggestions on a better way to do this?

 

[dhengr]

Canwesteng:
Why don’t you show us a sketch of what you think you have in mind at the moment. This should include all loads, forces, tentative member sizes, dimensions of the structure, etc., so we can better understand what you are really trying to do. You have to know what info. is important to solving the problem and to generate a meaningful discussion. I’d bond the Teflon to a bearing pl. and grout and anchor bolt that to the pier (elevation control and positioning). Then put a slide pl. (surface) on the col. base pl. and fix the col. base pl. to the bearing pl., and guide its motion at the same time, with some appropriate detailing. You need to be careful that a detail like this doesn’t fill up with crap, and become inoperable. You also have to brace the col. to take these loads and motions. Any uplift just adds to the problem.

 

[canwesteng]

I tried to be pretty general in my first post. It's a W10 beam sitting on a pier with a long pre eng building on it, ballpark about 10mm of thermal shrinkage from install to wintertime. The idea of a bearing plate with Teflon on it grouted to elevation seems similar to what I'd like to do. As I only want sliding in one direction (much less shrinkage in the other one) I don't think it needs the guides you've mentioned.

 

[a2mfk]

I would think you would have a base plate with leveler nuts, get your elevation dialed in, fill the gap with grout, then put the teflon pad on top of the plate.

 

[dhengr]

Canwesteng:
But, being general and misleading or incomplete, is no good for anyone. You gotta give all the needed info. to really start to solve the problem, to the best of your knowledge. Some of you guys have a way of making your questions so damn general that nobody can make a meaningful judgement about what you are trying to do, or the magnitude of things. It was a column, now it’s a W10, which you better have web stiffeners on at the bearing pl., so it can’t roll over. What are the various loads, vert., along the beam and perpendicular to the beam, and from what? What’s atop the W10, show a sketch? You probably have to guide the movement, or it can move any which way, and you may not want that. You need to cover and protect the slide surfaces so they don’t get full of junk over the years, and you have to cover any slotted holes for the same reason. If the slotted holes fill with rust or some such, they will bind-up. In terms of bracing and thermal movement, why is this bldg. different than any other long steel bldg.? What’s really going on at this bearing pier? We don’t normally provide sliding bearings.

 

[canwesteng]

I'm aware that I'll need web stiffeners. The slots should be able to be covered with washers without problem, they 3/8" each way. It's a long modular building, so while typically a long steel building would be designed for thermal contraction in the connections and not at the base, this is just welded frames that will shrink as a whole unit IMO.