Steps in structural slab
Steps in structural slab
(OP)
Hi,
Please see the attached sketch and comment on acceptability of the rebar details at step location. All suggestions are wellcome. I need to know if someone has practically done any other detail for large spans and for steps larger than slab thickness.
Please see the attached sketch and comment on acceptability of the rebar details at step location. All suggestions are wellcome. I need to know if someone has practically done any other detail for large spans and for steps larger than slab thickness.






RE: Steps in structural slab
RE: Steps in structural slab
If stress reversals are possible, from patterned or vehicle loading I would also try to lap top steel to top steel in a similar fashion.
GJC
RE: Steps in structural slab
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab
RE: Steps in structural slab
See attached sketch.
RE: Steps in structural slab
RE: Steps in structural slab
RE: Steps in structural slab
What if you have 6" sawtooth stairs for say 15' span.
RE: Steps in structural slab
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab
RE: Steps in structural slab
I'd be interested in seeing that detail.
I can't see how it can be done. Or perhaps only when you have a very long transition, ie. a shallow slope.
RE: Steps in structural slab
I think you misunderstood paddingtongreen. He is talking about typical stair slab framing in answer to canstructural's post.
RE: Steps in structural slab
RE: Steps in structural slab
Mike McCann
MMC Engineering
RE: Steps in structural slab
Yes, you're correct. I missed the embedded question.
Attached shows how not to reinforce stairs.
RE: Steps in structural slab
Or, literally turn the step itself into a concrete beam with the slab spanning to the top, and to the bottom of the beam.
Mike McCann
MMC Engineering
RE: Steps in structural slab
apsix,
I think the sketch you attached is for information only, it can't be built like that. You need closed hoops or other rebar arrangement for continuity.
See sawtooth stair design chart as attached.
RE: Steps in structural slab
can you please inform us on what the plan looks like becuase in the transverse direcetion that step is going to behave like a beam.
As already has been posted you will need continuity of the bottom reinforcement.
RE: Steps in structural slab
RE: Steps in structural slab
In short, I would put a support under the step and work out the moments and reactions, then I would remove the support and load the step with a load, the magnitude of the reaction I just removed. Then I would add the results of the two cases. All this on paper, of course.
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab
That step is about 50 ft long, so no possibility of treating it as a beam and no possibility of column too in that line. It's architectural requiement here, i already fight for this early to avoid this situation.
Thanks.
RE: Steps in structural slab
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab
There is nothing there to support that step. All galzed curtain walls below with deflection track.
RE: Steps in structural slab
I wouldn't build a sawtooth stair like that without continuous support at the sides.
As to your slab fold, I have seen a lots of them built with a detail similar to your Option 2, without any problems to my knowledge. However, research has shown that these joints are not as efficient as the straight slab, particularly for the opening joints, which in your case would be the lefthand part. European practice dictates the use of 'hairpin' bars, and Nilsson in 1972 conducted tests showing about 80% efficiency with that arrangement. Further tests showed that 100% efficiency could be obtained with transverse stirrups and tension diagonals.
RE: Steps in structural slab
RE: Steps in structural slab
Run the important pieces of reinf'g. stl. past the reentrant (inside) corners and embed and develop them in at the far face, and around a bar running parallel to the step. Maybe add a few extra pieces of reinf'g. stl. over the adjacent col./bm. lines to beef them up a bit (some two way slab action) and allow the slab to cantilever, somewhat, to the up turned or down turned discontinuity. Good luck on your stepped slab. If you don't mind too strenuously, I would like to steal your thread for a moment.
Paddingtongreen:
Boy, you must be an old guy, like me. You actually know what moment distribution is and how to do those calcs.? Maybe that's how we gained some intuitive understanding of how structures really work, deflect and react. Not that we always got it right on the first try though. Some of the younger engineers don't have that same intuition, as early in their careers, because the computer doesn't require that same thought process. Of course, with the computer we can change a few sizes and variables and rerun it in less time than it took us to readjust our slide rules.
Hokkie66:
In another thread, you mentioned that Prof. Richard Barker, drummed your early concrete design into your head during several college courses. I took my first concrete design course from him in about fall or winter of 1963, but that spring he left the Univ. of Minn., and apparently went directly to Virginia Tech. He was really a good teacher and a nice guy, I had some contact with him a couple of times after he left here. I don't think he was a full Prof. here, and the course I took from him was an elementary conc. design course for architecture students. That's what I thought I wanted to do with my life until I took his course and similar elementary courses in steel and timber. Seemed that I was better at and liked structures more than arch'r. I never could figure out how the make it canti. 300' without some structure, but that's what our arch. profs. wanted in our arch. designs.
RE: Steps in structural slab
Yes, UM's loss was VaTech's gain. I took my first course taught by him in 1964, so your memory would be correct.
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RE: Steps in structural slab
Anyways what your concerns are? No supports are allowed at sides of steps to make a beam spanning 50ft.
dhengr,
Attached sketch for what you meant, somtimes interpreting words are dangerous.
RE: Steps in structural slab
I did not suggest making the slab fold a beam. That was someone else. My comment about sawtooth stairs was just that I wouldn't do it. You introduced the idea of sawtooth stairs to the discussion, and there is no logical reason to build sawtooth stairs spanning parallel to the flight.
RE: Steps in structural slab
RE: Steps in structural slab
RE: Steps in structural slab
RE: Steps in structural slab
Let's make this a new starting point and offer some improvements on this for canstructural.
It's funny, I "speak" English English and American English; I just came from an English site and kept on using English spelling when I got here.
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab
I forgot the diagonal bars, I usually add #5@12" at re-entrant corners in tension, always provided there is room.
That would be #16@300, but if "canstructural" indicates Canada, it would be 15M@300
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab
RE: Steps in structural slab
Anyway, one "Z" bar can be used instead of two "L" bars if the joint is eliminated.
Just thinking about it, the fast track guys I worked with would have set the rebar for the lower slab and the dowels for the step and would be finishing off the rebar in the upper slab while the concrete was placed in the lower slab.
Okay rant over.
BTW, hokie66, you spelled programme English style after I went on about switching back and forth.
Timing has a lot to do with the outcome of a rain dance.
RE: Steps in structural slab