Top of Steel vs Deck Bearing
Top of Steel vs Deck Bearing
(OP)
My firm has used "Top of Steel" elevations noted along side the beam designation for years. Once the project goes out I try to ask the detailers and the contractor about our drawings and what we could do better. I have heard from detailers that "Deck Bearing" elevations would be helpful, particularly on more complicated roofs. I'm wondering if it's worth switching? My boss who has worked for large firms (100+ employees) says that that they used Deck Bearing when he was just getting into the field. Perhaps a switch to "Top of Beam"? Would Deck Bearing be confusing for the contractor? Just looking for other opinions. Thanks






RE: Top of Steel vs Deck Bearing
RE: Top of Steel vs Deck Bearing
RE: Top of Steel vs Deck Bearing
Also you may have a situation with a sloped beam, or a sloped deck bearing on a bent plate, where you may need to call out multiple TOS.
RE: Top of Steel vs Deck Bearing
The problem with Top of Steel (TOS) is that if you use a joist system with 2 1/2" seats, and you label TOS on the plans, you run the risk of confusion over whether the top of steel is the north-south bearing steel or the east-west top of joist steel. Remember that in joists, some beams are 2 1/2" lower than their orthogonal beam cousins.
The use of BMD creates a consistent definition of the plane of the roof deck and steel fabricators can easily detail the steel to be correct in creating the elevations you need.
RE: Top of Steel vs Deck Bearing
Sorry for hijacking, but I think it is on the same page as original question.
RE: Top of Steel vs Deck Bearing
RE: Top of Steel vs Deck Bearing
Also use JST BRG = joist bearing elevation, as necessary, for when joists are bearing on or connected to a CMU or concrete wall. With odd geometries and slopes, sometimes also supply the joist seat depth or say "sloped joist seat".
Haven't been doing much steel design lately, but elevations were one of the more annoying aspects of doing structural drawings. I'd rather design the steel and connections and have somebody else coordinate all that dimensional stuff- which in fact, many a good structural CAD tech can work most of that out with the architect.
RE: Top of Steel vs Deck Bearing
If the beam slopes, then you have to use TOS at each end of the beam - again you can probably do it on each beam individually to avoid confusion.
Usually we have a 1/4"/ft. sloped roof and we like to delineate the elevations on the main grid lines. This is where the confusion comes in if you use TOS.
If the TOS is labeled on the grid line - and refers to beams on the grid line, then that would work - but there are also perpendicular beams that would be 2 1/2" higher and
we always feared that confusion would result from that - especially in unique areas with a lot of jogs in the roof layout, re-entrant corners, etc.
RE: Top of Steel vs Deck Bearing
On other projects, top of steel is the most appropriate. Either way we need to give the detailer all the info.
RE: Top of Steel vs Deck Bearing
1) I like that TOS makes shop drawings easy to check. I've always understood TOS to essentially mean "top of non-joist steel".
2) I feel that u/s of deck reduces my liability somewhat. If I've failed to consider something in a complex situation, the steel detailer should still at least know where the steel has to get to at the end of the day.
3) The main reason that I use underside of deck now is that it seems to yield a better coordination review from the architects that I work with. They seem to think in terms of top of deck. Underside of deck's a pretty short leap from there.
RE: Top of Steel vs Deck Bearing
KootK: {Item 3} Interestingly, what sparked my question was getting an email from an architect reading me the Riot Act for showing Deck Bearing. In his opinion I was providing "meaningless information" which he "cannot use" and would only serve to "confuse the detailer and contractor".
So for his projects I'll have to stick with TOS/TOB.
Thanks again.
RE: Top of Steel vs Deck Bearing
If you want to keep it in a general note UNO on the plan set, just state the top of steel for both the W sections and the steel joists. BOD is OK too, and more generalized still, and even applicable to the swimsuit issue.
Mike McCann
MMC Engineering
RE: Top of Steel vs Deck Bearing
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin