How do you guys deal with movement on long steel lake piers?

Thermal expansion on those long steel runs is a real beast, especially when you've got zero shade. If you're looking at a 100-foot run of steel, you can easily see an inch or more of movement between a cold morning and a baking afternoon. I've seen guys try to weld everything solid, and it usually ends with the pilings leaning or the welds cracking over time. You can't fight physics; that energy has to go somewhere. I usually lean toward using **slip joints** at the major transitions where the walkways branch off. What I do is weld a sleeve onto one section that slides over the main girder with enugh tolerance to move but not rattle. For the decking attachment, oversized bolt holes or "slots" are mandatory. If you're using steel joists, give yourself a good 1/4-inch of play in the bolt holes and use heavy-duty washers. It lets the frame shift without putting that sheer stress on the fasteners.

On the footing side, over-engineering the pilings helps, but only to a point. If the lakebed is sandy, those pilings will eventually start to "walk" if the expansion is pushing them constantly. I've found that driving them deeper into the substrate is better than just making them wider. If you can get down to a more stable layer, the piling acts more like a fixed point, but you still need that flexibility up top in the frame.

Don't forget the finish when you start adding these movement points. If you're using a high-zinc primer or powder coating, those slip joints are going to rub. I usually pack those sleeves with a marine-grade grease to prevent the metal-on-metal grinding from stripping the coating. It's a bit of extra maintanence, but it beats watching your pier turn into a pile of rust in five years beacuse the expansion joints wore through the protection.

I didn't even think about the lake water when you mentioned packing those joints with grease. Does that stuff stay put, or do you have to worry about it leaching out into the water when it gets hot? I'm just getting my feet wet with basic framing, so seeing an inch of movement sounds like a nightmare to plan for. Also, with those all-steel handrails, do they get scorching in the sun while they're expanding? I’d be terrified of someone grabbing a rail and getting burned, or does the lake breeze keep the temp down enugh?

For the handrails, I ussually swap the top section for a composite or Ipe cap. All-steel rails in July will blister your skin. As for the expansion, check out PTFE or UHMW plastic shim plates. You can sandwich them between your girder and the piling bracket. They handle the sliding way better than metal-on-metal and you don't have to worry about grease slicking up the water. Just make sure your bolt torque isn't so high that it locks the whole thing up—I usually use nylon locking nuts left just a hair loose to allow that lateral slide.

I've noticed the color of the steel makes a massive difference in how much it actualy moves. If you're going with a dark powder coat, that frame is going to soak up way more heat than a standard galvanized finish. I actually had a client call me once because their pier was making loud popping sounds at noon—sounded like gunshots. It was just the steel binding against the brackets because the slots weren't long enugh. For those perpendicular branches, maybe try using slotted 'L' brackets at the rim joist. It gives you a few inches of play without having to fabricate a full sleeve for every single connection.