Crane wind loads; AS1418.1-2002

[apsix]

The previous edition, AS1418.1-1994, specified what wind speed the in-service wind load should be based on. This was typically 20 m/s.

The current AS1418.1-2002 now only requires that the wind force is based on AS1170.2 (now AS/NZS1170.2).

Is there a consensus on how the in-service crane wind load should actually be obtained? I have still been using 20m/s, but the checker is asking awkward questions.

Thanks.

 

[OzEng80]

1170.2 service wind has been revised to 25m/s (in 2005) - speed is unchanged for regions A & W.

Make sure that your design wind speeds are clearly specified on your drawings (pretty unlikely that a crane jockey will be moving stuff around with winds of 90kmh - but better safe than sorry).

Cheers

 

[apsix]

Thanks OE80, but can you reference Clause numbers because I can't find them?

Regards

 

[OzEng80]

aspix

The wind speeds are given in 3.2. If you are referring to the actual reference to 25m/s it is in the 'Guidelines for serviceability limit states' in Appendix C of 1170.0. Note that this is an 'informative' section.

The only reference to 25m/s in 1170.2 I could find is in the preface(p3)which gives a vague reference to a recurrence of 1/25 being used for serviceability limit states (note that this was also a 2005 amendment).

Cheers

 

[apsix]

OE80
I can see that the typical serviceabilty wind speed should be based on a 1/25 annual probability, in the amendments to both parts 0 & 2, but there's no reference to 25 m/s or to crane in-service wind speed that I can find.

Regards

 

[OzEng80]

Apologies apsix

I have been thinking ‘recurrence’ and typing ‘speed’....
Your design wind pressure has to be calculated from the 25 year recurrence and site specific factors - if it is to come from 1170.

I think the only place a specific wind speed specification (like 20 or 25m/s) suitable for design could come from would be the crane operation code (AS1418).

If you have to design it for serviceability loads in accordance with AS1170 you are stuck with the 25 year recurrence.

That said I think that it is unlikely that crane jockeys will be tackling the higher wind speeds this affords them!

I’d either find crane specific operational speeds (and include it in your documentation) or argue that AS1170 speeds are serviceability speeds not ‘in-service’ speeds.

Sorry for the confusion.

Cheers

 

[apsix]

Thanks Oz
As the allowable sway deflection of the portal frame supporting gantry cranes is only 10mm I certainly will be arguing that the 25 yr recurrence interval combined with the crane load is too onerous.

Regards