stair Design
stair Design
(OP)
Hello everyone, I am currently designing a stair with just one stringer HSS shape, with steel plates as tread. Someone told me that when you design a tread, you need to apply the 100 psf and a concentrated load of 300 pounds. I am not sure where to apply the 300 lbs. If someone please could help me. Thanks
RE: stair Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: stair Design
For a typical 44 inch wide tread having an 11-inch effective depth, the load per tread is 336 lbs.
RE: stair Design
RE: stair Design
My interpretation of ASCE 7 for the minimum design of stairs is 100psf OR 300lb point load. They do not need to occur simultaneously. I always check the uniform load and then I check a 300lb point load (4in^2) at the worst location and make sure my design is satisfactory. Hopefully others can confirm.
EIT
RE: stair Design
I wouldn't apply the 300# concurrent with the 100 psf... You might apply the load at the edge of the tread for max effect.
Dik
RE: stair Design
RE: stair Design
Thaidavid
RE: stair Design
RE: stair Design
RE: stair Design
RE: stair Design
My point is that the concentrated load case controls for grating style stairs and don't ignore it. For concrete, I'm sure it's not a problem.
Also, maybe the 300 lb. requirement needs to be changed. We all know guys (and some gals) that push 350 lb. Look at the offensive line for an NFL team. Or a weight watchers meeting. And these people will take the stairs two at a time.
RE: stair Design
RE: stair Design
But to further dnlv's point, the same Table 4-1 of ASCE 7-10 permits uniform load of 40 psf for 1-or-2-family dwellings instead of typical 100 psf. The 300-lb point load still applies.
A gray area might be a part of an apartment/condo complex where the staircase leads to just a small portion of an upstairs area that is only utilized (in general) by 1 or 2 families. I would stick with the 100 psf even for this scenario and avoid the need to have that argument later.