Crane impact factor

[JRGse]

When designing runway beams, brackets, etc. what would be the more appropriate vertical impact factor to use for a radio-controlled crane, 10% (pendant-operated crane) or 25% (cab-operated crane)?
I cannot find this info in AISC, ASCE, etc. but my thoughts are that since a person does not need to walk with the crane, the 25% impact factor would be more appropriate.

Thanks for the input.

 

[ToadJones]

According to good ole' AISE tech report 13 you should use 25% with radio operated.

 

[ToadJones]

the reason being, operators get kind of foolish when then can operate the crane from afar via a radio

 

[ToadJones]

Also, page 49 of AISC DG 7:
"Cab operated or remotely operated" = 25%
Radio = Remotely

 

[JRGse]

thanks

 

[FLCraneBuilder]

Wow - this one caught me off guard. Review of Tech 13 confirms Toad's statement (and I also agree with his foolish operator's thought)

A couple other notes though:
1. Approximately 40% of the hoists sold these days use VFD motor controls which provides very soft starts & stops of hosit motion - hence reducing verical impact. We will allow a beam closer the edge when we know VFD hoists are being used.
2. We tradionally try to keep our delfections down to about 80% of allowable. Mostly due to customer perception concerns. Very often, a next size deeper beam will have the same weight (cost) and still be OK in the other charecteristics.
3. For the Crane's girder design, CMAA directs that we increase the impact factor when hoist speed increases:

15% minimum
.5% per fpm of rated hoist speed, but not exceed 50% unless magnet of bucket duty.

Interesting how this is so different from Tech 13

Note that impact is not used when running deflection checks.

 

[vandede427]

seems like we talk about this topic at least once a week.