Ladder design example per AISC

[Nitesh Sadashiva]

Hello all,

Can anyone help me with the ladder design example? AISC design guide 34 gives information on the stair and handrail design but not on ladders. I couldn't find any reference for ladder design and its connections. Usually I do connection design. I haven't done any miscellaneous steel design earlier. Now fabricator want me to design the ladder and submit the calculation for EOR.

 

[WinelandV]

Being the fabricator's EOR is such a fun time...

So, yes, you don't find examples, b/c ladders are typically a standard off-the-shelf design.

As for actually designing a steel ladder, what I do is assume a 300# load on the ladder, but not acting at the midline of the ladder - I assume 30" off of the centerline b/c OSHA requires all head-knockers/interferences to be a minimum of 30" from the ladder. So, I'd put the 300# on a single rung and add about 250# for the force due to the moment couple (M = 300# * 2.5ft = 780 ft-lbs; 750 / 3ft = 250# --> the 3' is the assumed distance between hand and foot). check your rung for the vector sum: ~ 400#. Assume the rung is simply supported for the bending check, even though you're going to have the fabricator weld all-around each end.

To design the side rails, you get a nice compression + moment design. If you want to be super-conservative, assume that all the load is on one rail. I assume the rungs will brace the weak axis, but that the strong axis will likely be the distance between the platforms (unless there are brackets tying it back to the wall at a given spacing - however, I imagine you have a ladder not a wall, which is what is prompting the request for calculations). Obviously, the compressive load is the 300# plus the self weight of the ladder/rail, as well as the 300#*2.5' moment. Unless you're using a funky shape for the rails, you're going to be using F11 of the AISC 360, and will likely be in the Lateral-Torsional Buckling portion.

Hope this helps, and good luck!

 

[david339933]

ANSI ASC A14.3-2008 (R2018)

 

[dauwerda]

PIP (Process Industry Practices) publishes both a design guide and typical details for fixed ladders.
PIP STE05501 Fixed Ladders Design Guide
PIP STF05501 Fixed Ladders Fabrication Details

The most current revisions were released in July of 2018 to align with the recent changes to OSHA requirements.

 

[dik]

I have a criteria that I use and ask the EOR to confirm, and put the onus on him.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[SJBombero]

When fabricators ask for a design, I prefer to have them detail it about 50% first and then I justify their design. Especially if you don't have standard details ready. They have most likely done built something similar before and know how they want to do it. If you just design it the way that's most efficient for you, they will likely come back with change request to realign the design closer to their standard.