Seismic load on Overhead Travelling Crane 4

[mte12]

Does anyone have experience with seismic load on an overhead travelling crane.
This is for design of supporting steelwork, not the crane itself.
It is complicated to understand.

Specifically, are there any design prescriptions that have made their way to codes/standards.
- Magnitude of loads.
- Is the hoisted loads considered?
- What if it's a low duty crane, can load be discounted altogether?
Etc.

 

[DoubleStud]

Typically the crane company supplies the loads. They will give you the reactions and moment at each column.

 

[MotorCity]

Doublestud - the crane company does not compute and provide the seismic load. The EOR does that based on the project location and the crane operating loads provided by the crane supplier.
I have never had a crane supply provide the reactions and moment at a column, but maybe you work with a different type of crane supplier with those capabilities?

mte12 - Unless the crane is operating continuously, we typically do not include the weight of the hoisted load in the seismic load. Even then, there is a period where the crane has no hoisted load (between setting and picking a load).
For low duty, just assume the weight of the crane itself contributes to the seismic load

 

[SandwichEngine]

I've been told that you never have to consider the lifted load because it will act as a damper if a seismic event hits while the crane is lifting a load. You would consider the weight of the crane itself and the crane beams.

 

[GC_Hopi]

My experience is that the seismic loading is given by the crane manufacturer and I just reviewed a shop drawing where that was done.

I believe ASCE has language that you dont consider the lifted load for the reasons mentioned by SandwichEngine.

 

[mte12]

Thanks to all for the input.
I have read about the hoisted object not been included, but also saw this paper which infers that for given scenarios the seismic load transferred to the supporting structure, in the lateral direction, is increased by the presence of the hoisted object.

I don't have an issue with not considering the hoisted object for a low duty crane, however often see minimum requirements in codes/standards. That's one of the main concerns.

 

[HTURKAK]

I will suggets you to look AISC DESIGN GUIDE 7..
The following para. is copy and paste from the same..

( 13.6 Seismic Loads Although cranes do not induce seismic loads to a structure, the crane weight should be considered in seismic load determination. The seismic mass of cranes and trolleys that lift a suspended load need include only the empty weight of the equipment. The designer should carefully evaluate the location of the cranes within the building in the seismic analysis.....)


I would like to remind also that some codes take into account some portion of hoisted load for vertical seismic effects ..

















Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

 

[mte12]

Thanks HTURKAK, this is very useful to know.