Staircase

Start at the bottom and work your way up.

Consult your local safety standards for requirements as to step size (width, depth, rise, tread, overlap, angle of rise) and maximum height between platforms.

Because of the 270deg restriction, you have only 11.25m horizontally to work with, which will reduce to about 10.25m because of the platform. This makes your rise/tread proportion equal to 15/10.25, which may be steeper (55.7deg) than locally allowable.

Maybe you can consider an alternating-tread design, if permissible.

Good analytical response. I this the op hosed up on the diameter units thou.

I don't understand your 2nd sentence. Can you translate?

I hosed up on that too... :-)

Replace 'this' with 'think'

Your calculations does not have details, it's just numbers. If it had details it would at least have units.

That would be a tall thin tank, though of course not impossibly so. Tanks are usually made to a specified dia, not circum. Not 15m dia by any chance?

API 650, 620 and 653 are silent about staircase. But you can get information in
OSHA Doc. 3124-12R 2003
"Working on and around stairways and ladders is hazardous. Stairways and ladders are major sources of injuries and fatalities among construction workers for example, and many of the injuries are serious enough to require time off the job. OSHA rules apply to all stairways and ladders used in construction, alteration, repair, painting, decorating and demolition of worksites covered by OSHA's construction safety and health standards".
WP

That's a good example of tackling bona fide design issues with pure drivel. So like a bureaucracy.

JeJe you're so funny. You have something to share?

See post 3, which actually gives valid information. Then shut up.

I get bored, maybe a coffee and watch something on TV........

WP

Detailed Calculation

What?

He's having a laugh IMHO

Who is having laugh? I prepared one excel sheet based on this question.And Just changed couple of values, and posted it for peer review.Got one off-topic rating.Genuine spare part is still in my hard disk and the mathematiks used to solve this issue is very simple.

Sanweld, add some more information as to what these numbers mean. We don't read minds

OK but from the information in #13 there's no way we can tell what your calculating. Also a lot of spurious accuracy! But on a more general point, as often happens we've heard no more from the OP, although several posters have tried to help. I wouldn't mind an answer to basic query in #4.

Or coordinates to something spectacular

Are the stairs on the inside or the outside of the alleged tank? Do they start at the top or the bottom?

Why would you come to the forum and ask a question with no basis in reality?

Hopefully it is just homework, and you have no real position in the construction of such stairs!

Google "homework help".

Hire a journeyman welder or carpenter...the magic number might be near 17 if you do your calculations in inches, it depends on how comfortable you want to be when ascending or descending...or you might want to turn part of it into a "ladder".

This is a very old post I have only just joint the site so I don't know if this will be read previous posts have been a little aggressive.

Your given little info but assuming that the stairs are on the outside of the tank, calculate you path as the circumference not the shell and stand off the stringers from the shell far enough to get the horizontal dimension for the angle required.

The design is still in your court I believe that to be a solution.

That approach could be successful. My earlier quickie calcs were based on the o.d. of the tank, but using the o.d. of the stairs could reduce the slope enough to be OSHA-acceptable. (Or acceptable to local standards).

Quote "how i complete staircase for this tank within 270deg angle with 1 platform."

Get some steel and a welder. Start 17M away in an easterly direction and put the first platform at 7.5M high and build 2M towards tank. Make first staircase up to landing from 32M away and then make second staircase from landing to top of tank.

I am assuming you want to go to the top of the tank. If not, ignore my post.

Maybe you want to go around the outside of the tank for the first half then put the platform through the tank wall to join to the second half inside the tank. Or is it the other way round?

Seriously 'though;-

Once you have defined what you want you will be better placed to work it out for yourself. Get a piece of paper 15cm by 15cm and roll it into a tank shape, mark on it want you want and that might help you as well.

Jim

You have almost everything you need to make the calculations yourself. This a really good homework brain teaser. My answer is call the tank builder and ask them to install it. Give them the dimensions and listen to them laugh at the ridiculousness of the specifications. Try this instead:

Here is a scale model of the tank. LOL!! The dimensions do not make sense?

1. 15m Circumference = 15.6 ft. diameter = 187" Dia.
2. 15m height = 49 feet = 590".
3. The staircase specifications are 3/4 the way around the tank = 270 deg.
4. A typical step is approx. 8" in height and 12" in depth = 8" rise with a 12 " run.
5. These are rough measurements and I'm rounding to make this easier.
6. 590 / 8 = 73 steps.
7. 187 * 3.1416 = 587".
8. (587 / 4) = 146.75" * 3 = 440" on the circumference or 270 deg.
9. Assume a 36" platform 1/2 way up the tank at 24'.
10. 440" - 36" = 404" total length to install stairs.
11. 404" / 73 = 5" for your stair tread next to the tank and 7.125" away from the tank.

Here is a drawing of your stairs.

This design becomes more of a ladder step rather than a standard sized step.

I love nothing more than doing some student's home work assignment.

So, who really benefits from this interaction?

I don't think it's the student

I hope he doesn't use my numbers because my rounding puts the top step floating a few inches above the top of the tank being suspended by a Skyhook designed and built by LynDor® Industries (pictured below). I also like to throw a few other numbers in too just to mess with them. I figured that if I'm given a theoretical problem, I will give a theoretical answer. In Theory, a student should do their own homework, I assume!

I mentioned the 'magic' number 17" in an earlier response, i.e. 1 tread and 1 riser added together, it's the average persons comfortable stride when ascending. Also...this value should remain constant through out the run, if it varies by as little as 1/4 inch it can introduce a trip hazard as your mind gauges the step on the first few, and if it changes, you will stumble. A framing square and a couple of clamps makes layout simple, once you've calculated the 'rise' for the 'run'.

The OSHA "magic number" is 17.5 rather than 17. It is given as a permitted formula, but not mandated.

When I was a building Contractor in California, one of my specialties was custom decks with built in tables, benches, roof coverings and of course stairs. Yes the magic number is 17.5". however, I was building these custom decks for the client that owned the home and would design for their height and weight at the time of installation. I found that when you have a longer "run" on an exterior deck, especially around a pool, the larger step provides a much more comfortable position to stand on when your feet are bare or wet. You want to be able to support the entire foot, not just the "ball".

In my town there is some dumb contractor that builds 7.5 x 7.5 (or even smaller) Munchkin stairs. There may be some merit to oddball custom sizes, but if the building is sold, the stairs may be all but unusable for anyone else.

"Tread" alone means the net run, or horizontal pitch. "Tread width" includes overlap (or nosing) of adjacent treads. As you mention, larger tread widths are especially helpful in wet conditions.

I haven't researched history of it, but I'll bet the 17" was increased to 17.5" sometime in the last 50 years due to the increase in average height. (I joined Local 1243 as a journeyman millwright in 1969 and if I recall correctly at that time 17" was recommended.)

Try this Android App.

https://play.google.com/store/apps/details?id=appinventor.ai_davivalcesp.StairCalculatorCAD