AS1418 Hoisting application group 1

[yihshawn]

In AS1418 Cl 4.5.3.3 there is a table categorizing hoisting application group for cranes (H1 to H4). One of the properties is the fundamental natural frequency of structure (vertical plane)- see table below.

However the standard do not discuss much about this "vertical plane fundamental natural frequency".

Do anyone know the proper definition of this term and how to find it?

 

[Joe591]

I take it that the natural frequency of the structure would have to be determined and then compared to the table. The same structure can have multiple natural frequencies. I think the natural frequency in the vertical plane would have to do with the up and down sway of the boom. Somebody would have to determine what that is. the natural frequency would also change depending on how much load is being lifted. It is not a simple topic. There is probably a industry standard for how the natural frequency should be calculated. Maybe the manufacturer of the crane would be able to help. Presumably they would have had to calculate this or test for it at some point during there design or testing phase.

 

[PersonalProfile]

I cannot directly assist, however I observe that table was apparently extracted from a superseded version of AS 1418, refer following summary of latest:

https://emergentgroup.com.au/cranerequirement/

 

[Tmoose]

First bending mode of a simply supported beam is the upper image here -

https://cdn.comsol.com/cyclopedia/eigenfrequency-analysis/Eigenmodes-of-simply-supported-beam.jpg

I picture the crane probably is supported at the ends on two rails, and those rails are supported by columns every now and then.
As the crane runs along those rails the vertical rail stiffness varies upon how close they are to a post.

As a result the crane's first bending mode ( and all bending modes) look more like shown in the attached " mode shape vs bearing stiffnes .png".

Note The actual natural frequencies are significantly numerically lower than the natural frequencies calculated for ( mythical ) rigid supports.