Factor of Safety for Overturning - Foundation Design 1

[oengineer]

I am working on designing a foundation for a jib crane. [highlight #FCE94F]The jib crane is 16 ft tall with a 24 ft cantilever arm. The maximum lifting capacity of the crane is 3 tons.[/highlight]


From CRSI Design Handbook 2008, it mentions to use a Factor of Safety (FOS) of 2.0 for Overturning, see image:

A FOS of 2.0 is also mentioned in Principles of Foundation Engineering, 8th Edition by Braja M. Das:

However, it seems PIP mentions the use of FOS = 1.5 or 1.2 for overturning, see images:

The only explanation to these various FOS I could find is mentioned in the Foundation and Anchor Design Guide for Metal Building System by Alexander Newman:

For my particular situation, what would be the appropriate FOS for overturning to use for a jib crane foundation based on the crane description I provided above?

I am inclined to use FOS[sub]overturning[/sub]=2.0, but I would like to have justification for my design which ever route I go.

Comments/suggestions are appreciated.

 

[BAretired]

Unless the crane motor cuts out when the load exceeds rated capacity, a FoS of 2.0 may not be enough. If an operator attempts to lift something exceeding the rated capacity, it would help to know the maximum lifting capacity of the crane.

BA

 

[HTURKAK]

Minimum F.S. 1.5 mentioned in ( PIP STC01015 Structural Design Criteria ) . The snap is below..

-The vertical weight of the jib crane will be included ..If the vendor provided the overturning moment & vertical weight of the jib crane , If the OT moment provided is based on capacity , plus a hoist & trolley allowance , add and an impact allowance (1.25) and wind effect. Vendor could not know if the installation is indoor or not and the wind load applicable at a specific case.

- If the criteria is F.S. > 1.5 , you may choose the dimensions of the ftg so that F.S. say 2.155 > 1.5 . ( still almost everybody look that the criteria is F.S. > 1.5 . (this clue is my personnel opinion ..)..

- Section 12 is for seismic design and clause ( 12.13.4 Reduction of Foundation Overturning ) is for the structures designed with (Section 12.8) .. and the jib crane is essentially inverted pendulum.. Moreover, the lifted load is not included for horizontal seismic load effects.

- I screened your previous responds and suggest you to ask the supervision of senior structural engineer..