Steel stair stringer 1

[IUD]

I am doing a design of a steel stringer . there is two PFC supporting precast concrete treads. According to code requirement i used 4kpa live load on tread.so point load on stringer say 1.5KN. my question is do we need to consider a situation where all the treads are full of 4kpa . so in stringer each and every point which connects to tread having point loads . is that correct or which way need to think? if anyone post an idea that would be helpful.

 

[DETstru]

Yes, you place the distributed load on the full horizontal projection of the stair.

 

[MotorCity]

Whats "PFC"?

 

[Ingenuity]

Whats "PFC"?

Parallel Flange Channel.

 

[thaidavid40]

Re: PFCs - other than rolling and cooling distortions, are there any channels whose legs aren't parallel to each other? Isn't PFC a redundant term?

Thaidavid

 

[DETstru]

http://www.tubecon.co.za/en/technical-info/tubecon-wiki/channels-taper-flange-parallel-flange.html

The channels we use in the US (typically) have tapered flanges. Not sure if anyone uses PFC's here or how extensively they're used worldwide.

 

[XR250]

I thought MC channels had straight flanges? I spec them regularly in the US. MC6x18's are real handy to attach shearwall straps to at the base of a metal stud wall.

 

[DETstru]

Yes, that's correct.

Maybe I'm mistaken that MC's are not used often. I hardly use them but others can chime in or say otherwise.

 

[Ron]

I routinely use MC 10's and 12's for stair stringers.

 

[hokie66]

Much of the world now uses parallel flange channels for the large ones, and tapered flange channels for the little ones.

 

[Ingenuity]

Much of the world now uses parallel flange channels for the large ones, and tapered flange channels for the little ones.

Like much of the world uses the metric system...except the US

 

[P1ENG]

Like much of the world uses the metric system...except the US

The rest of the world's loss. Who wouldn't want to use a unit of slugs?! I'm just glad we don't have to do a lot of mass calculations because lbm and lbf starts opening up problems.

Edit: Oh yeah, I meant to also say something relative to OP's question. In the US, we need to design the entire horizontal projection with 100 psf [4.8 kPa]. Each tread also has to be designed for a single point load of some magnitude (can't think of it right now; I'm thinking either 300 lbs [1.33 kN] or 1000 lbs [4.45 kN]). That point load is applied at center for bending check and at the end for shear check.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[Bagman2524]

The concentrated design load is 300 lbs. All the treads need to be assumed to have 100 psf on them to account for the stair to be full of people using it due to evacuation or whatever else might cause people to pile into the stairway all at once.

Nearly all men can stand adversity, but if you want to test a man's character, give him power. Abraham Lincoln

 

[IUD]

Thanks for all your comments and ideas.

Further I need to clarify something. I need to design a base plate for newel post in this stair . as per the attached sketch i use 4 bolts for the connection. is it require this newel post exactly be in middle or any arrangement as per my sketch is ok?

 

[IUD]

Also I am using a 75mm pocket in foundation to put this base plate . and use non shrinking grout below the base plate and on top of the base plate to hide the base plate. further is there any issue if we put another layer of concrete to cover the non shrinking grout on top of the base plate?

 

[Bagman2524]

Not sure of UK or European requirements but there are no requirements for newel post locations in IBC. They merely need to be able to support the design loads. And keep openings in the Guard to 4 inches or less. The Architect might not like the look if it's unsymmetrical.