IBC Impact Loads (Machinery)

[StrucPEng]

This may be a very straight forward question but I want to make sure I am designing for the correct loading one of recent projects. I have a piece of machinery that requires new supports. I have the raw weight of the machine and I am looking to obtain the factored load to design to. I see that the IBC (I am using 2015) 1607.9.2 Notes a 50% increase for reciprocating machinery (which is the case in my situation). I want to make sure that the intention of this is to take the raw weight say 5,000 lbs and increase it by 1.5X = 7,500 lbs, then use that amplified weight in the load combinations to land on a factored design load. Basically my question boils down to the provision for impact loads (1607.9.2) is a factor that is used in tandem with the traditional load combination factors not one that is use in replacement of the load combinations.

Additionally, I assume a piece of machinery which is stationary in its position but has a motion to it (hence the reciprocating machinery factor) would be treated as a live load when applying the load combinations (1.6L).

Thanks for everyones help!

 

[WARose]

Reciprocating (anchored) machinery isn't my idea of the applicable situation for a impact factor. Impact loads are more of a short duration situation. The impact factor probably wouldn't hurt.....but you could get a lot better idea of the transmitted force from a dynamic analysis. (If it is required.)

I'd treat the machine weight as dead load.

 

[StrucPEng]

Thanks for the reply WARose. I should maybe clarify a bit. This machine has a motor driven section that is extended and retracted periodically. This happens maybe 20-25 times in the course of a day, so that was my reasoning for adding the impact load factor as it is not a constant occurrence. I wanted to be covered if (and when)the machine stroke were to max out and abruptly stop.

 

[WARose]

That makes a bit more sense. (Although "periodically" (in my mind) isn't 20-25 times day. )

I get that you want to be covered for this.....but you may have to dig a bit more to be certain of that. I'd contact the manufacturer to know what kind of load is generated when the "machine stroke....max[es]" out. The impact factors in the code won't cover you for all situations (as impact factors can certainly be greater than 50%).

 

[StrucPEng]

I think that is a good idea, I will reach out and see if I can get some more specific loading information from the manufacturer. Thanks for your help!