Scale Verification according to ISO 14122-4 standard

[Stéphane_YVART]

Hello everyone,

I check a cage ladder that equips a removable maintenance walkway. This ladder is in 2 parts because the lower part must be able to be removed when this footbridge is stored on the ground. The scale is therefore composed of:

• a fixed steel part welded on the gangway with a cage and an access gate
• a removable part which is a commercial aluminium ladder and whose first 2 upper rungs are housed in hooks provided on the fixed part

The objective is therefore to verify:

• The removable aluminium ladder due to its unconventional use (support via the rungs)
• The fixed ladder, especially the part with the support hooks

For load cases, I base myself on the ISO 14122-4 standard but I have a little trouble interpreting the simulated loads presented there; We have:

• An F1 load applied to a rung, over a width of 100mm, which logically corresponds to the load of a user via one of his feet resting on the rung, (standard value 1.5KN)
• An F2 load that seems to model the load of a user holding on to the uprights (standard value 1.5KN); it is a remote load but the area of application is not specified (for my part I considered an area of 100mm at the back of each upright and horizontal of F2 which corresponds to the hands of the user...)

I have a bit of trouble seeing if these solicitations should be applied simultaneously or each separately.
Simultaneously: we apply 2 times the user's load, which is very overloaded for the calculation
Separately: for F1 alone we can consider that the user climbs the ladder near the uprights by holding on to the rungs and neglect F2 but if we apply F2 alone it is equivalent to considering that the user holds on to the uprights but has no foot on a ladder rung...

I don't really know if I'm asking myself too many questions or if I'm completely wrong...

Does anyone have an idea?

In p.j.:

A diagram of the loads applied simultaneously (F1 + F2) on the fixed scale via the 2 lower brackets. Let's take the most unfavorable case with 2 users on the aluminum scale:

A view of the loads applied for the verification of the aluminum ladder this time:

Thank you in advance.

[FRED78]

Hello @Stéphane_YVART
Isn't there a standard that explains how to apply the calculations (eurodode xxx)?

[FRED78]

In your calculation, it seems to me that you have to calculate in several places with the same load. The behavior of a ladder as you press the first rung, or the middle rung, or the last one, the solicitations on the ladder are not the same.
To my humble avi

[Stéphane_YVART]

Hello @FRED78,

To my knowledge there is only the 14122-4.
The load cases are quite explicit but it's especially the fact of having 2 independent load cases that appeals to me.

[m_blt]

Hello @Stéphane_YVART ,

In the absence of knowledge of the 14122-4 standard, I give you my thoughts on the use of the ladder, which can lead to certain observations...

If we consider the balance of the climber alone, the efforts concern only his weight, offset in relation to the plane of the ladder, and the actions on the rungs in contact with the feet and hands. In my illustration, climber and backpack have a weight of 1130 N. Actions on the rungs: 824 N at the level of the foot, and 424 for the hands.
The force on a bar (increased to 1500 N) would correspond to the first load case of the standard.

If we consider the {climber - ladder} assembly, it is the fasteners of the ladder that come into play, especially if it is fixed by hooks at the level of the upper rungs.
For a weight almost identical to that of the first model, the forces on the hooks are significantly greater: 855 and 1575 N.
This case may explain the second simulated load case of the standard...

[FRED78]

@Stéphane_YVART
See the NF E 85-016 standard?
In MP possibly

Provided that the design of your ladder complies with this standard