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Small Cantilevered Platform
5

Small Cantilevered Platform

Small Cantilevered Platform

(OP)
I have a small, 6' high cantilevered platform constructed from HSS. It is for a single person and will be designed for a loading of 300lbs. It is cantilevered from the HSS post attachment at the base to concrete, secured using Hilti chemical anchors. The loads are likely capable of being resisted by Tapcon (I'm not too keen on).

In past, when I've designed these, I usually consider a lateral loading of 15% of the vertical loading at the platform level. Is there a code or standard that recommends something else, that anyone is aware of?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

Asce 7 - 1.4.2 minimum lateral force of 0.01Wx.

RE: Small Cantilevered Platform

We don't use the same code however for ULS I use 10% of the vertical loading as per our seismic code.

For serviceability I use 1kN lateral and would prefer to see deflections up to 2mm-3mm. This is my approach for ensuring that people moving around the platform aren't subjected to excessive vibrations. This approach is an amalgamation of my code and personal experience. The AS code allows plenty of wiggle room in serviceability criteria. Customer satisfaction allows less wiggle room and for the sake of 5% extra cost a rigid platform will please the clients.

RE: Small Cantilevered Platform

I don't know if this is applicable in your case, but I might consider an eccentricity due to the person hanging off the side of the platform. So, the 300 lbs load with an eccentricity of an arm's length, or about 3 ft.

RE: Small Cantilevered Platform

(OP)

Quote (Asce 7 - 1.4.2 minimum lateral force of 0.01Wx.)


1% seems awfully low. I use a higher value to minimise any 'wobble' when someone is on the platform.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

(OP)

Quote (So, the 300 lbs load with an eccentricity of an arm's length, or about 3 ft.)


I've considered that for ladders, but not for platforms... sounds like a good idea; I'll work that into a solution.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

(OP)

Quote (We don't use the same code however for ULS I use 10% of the vertical loading as per our seismic code.)


I'll take another gander... 15% may be a little high. Maybe a smaller percentage and/or a minimum load. Are there any other agencies that stipulate a loading?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

Quote (dik)

I'll take another gander... 15% may be a little high. Maybe a smaller percentage and/or a minimum load. Are there any other agencies that stipulate a loading?
Depends what load you are factoring really... I wouldn't object to 15% being too conservative for a small structure. My rule of has been mostly just a rule of thumb. With it being justifiable from the seismic code for small structures in my region.

If I have a 3mx3m structure for personnel access only then my load is 2.5kpa so 22.5kN. 10% of that is 'only' 2.25kN, 15% is 3.4kN neither of which is excessive for ULS lateral. Both I'd suggest are excessive for serviceability loads.

Likewise if it is a structure holding a 10T static vessel then the 10kN lateral is likely an unrealistic figure in normal service conditions but in a seismic event it makes sense to have a lateral capacity similar to that (or even more depending on your seismic circumstances).

I normally find serviceability dominates for small access platforms for lateral loads. One company I worked for replaced their brand new 20mx0.75mx2m(high) aluminium platform because it was "too wobbly" and flimsy. The supplier was quite a reputable access system supplier, while I never checked it I have little doubt it was structurally safe. However the lateral movement of a 0.75m wide, 2m tall frame can readily be unsettling for users. The customer had a brand new high quality facility, the didn't want this wobbly access platform at the front of the facility.

RE: Small Cantilevered Platform

Dik:
I agree that the 1% is too low that is just an example of a codified minimum lateral force. 10-15% range is around where I tend to land on this also.

RE: Small Cantilevered Platform

(OP)
I've decided on using a 15% of vertical load or a fixed value, depending on what is the lesser. Most of the platforms are small about 1.5m x 2m (or less). For large platforms/mezzanines, I use a different approach.

Thanks Gentlemen (binary term for PC).

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

For platforms that small, make sure whatever lateral load you use is enough to cover the guardrail lateral force too. Usually that's not an issue, but if my conversion is right the 1 kN is just enough to cover the guardrail requirements here in the states.

Go Bucks!

RE: Small Cantilevered Platform

(OP)
Already done... thanks for the 'heads up' though... the tractions for applying the load were ignored.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

3
Sorry Dik, slow on the draw here, but ASCE 37 (design loads on structures under construction) wants 50 lb/person (e.g. 20% of the vertical personnel load).

RE: Small Cantilevered Platform

(OP)
Thanks, good to know... What part/article of ASCE 37?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

section 4.4 Dik.

They also say 2% of total vertical load.

RE: Small Cantilevered Platform

(OP)
Thanks... value added...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

Does one anticipate this being used overall as a fall protection anchorage?

There's that ASCE guide for petrochemical facilities, that might have something, but I thought it was for wind load. Yeah, wind/seismic, never mind.

There's that anchorage design one....ASCE Anchorage Design for Petrochemical and Other Industrial Facilities

Does that, what, 300 pound 18" from the face of the column OSHA thing apply?

RE: Small Cantilevered Platform

(OP)
No, but thanks... I hadn't considered this as a loading condition. I've revised the drawing to reflect this for the client to confirm.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Small Cantilevered Platform

(OP)
This was a good thread; I simply wanted to know if there was a standard that I should be using and could specify, rather than arbitrarily picking a load. It was quite informative.

Thanks gentlemen (binary term for PC)

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

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