Cambering of Steel Joists 2

[abusementpark]

I noticed that the Steel Joist Institute requires all steel joists to have a certain amount of camber depending on the top chord length. Do ever specify any deviations from this requirement?

I checked my company's standard specifications and found that they do not allow cambering of joists. However, I am not sure if this has always been enforced. I can see a situation where cambering could cause issues with the deck installation if you have two adjacent joists with significantly different span lengths.

What is your standard practice? Do you allow the cambering? Are there ever installation problems if you do?

 

[OHIOMatt]

We deviate from standard camber on nearly every project for the deck installation reason. If we have a bearing wall running parralell to the roof joists, we reduce the camber to 0 for joists within 3' of the wall. For joists between 3' and say 6' we allow 1/2 standard camber.

 

[abusementpark]

OHIOMatt - What about on long span joists (LH series) or joist girders? Do you allow camber for those type of situations?

 

[OHIOMatt]

For LH joists, we basically use the same rule as noted above. For girders, we typically go with standard camber. please keep in mind that this is for roof design. Floor design is a little different.

 

[abusementpark]

That makes sense. Right now, I'm looking at some roof joist girders with 100' spans. It seems like camber would be helpful on something like that. Thanks a lot.

 

[SteelPE]

On a project I just finished the design of a few weeks ago we ran into the same situation. I have some joists that are 125 feet long. We specified the joist next to the wall receive 1/2 the SJI camber in order to facilitate the attachment of the decking to a nearby masonry wall/structural steel.