impact load

[casasf]

I am working on a foundation design for an evaporator. The compressor VERTICAL loading at the supports are +/- 74 kips. The duration of the load is 10 ms. What is the recommended load combination we can use? any references?
Appreciate your response.

 

[TRAK.Structural]

Is this a true "impact" load where there is some sort of collision or dynamic action that produces impact? Is this load being produced as a result of wind/seismic lateral loads that are resisted by a vertical force couple from support legs? More information (and a sketch would be great) is needed here to help answer your question.

 

[GregLocock]

100 Hz? That's a bit exciting. Pun intended.

 

[hawkaz]

Is it motor driven, or reciprocating/power driven?

See ASCE7-16 4.6.3

 

[SWComposites]

mount the equipment on vibration isolators and then don't worry about it for the foundation.

 

[ANE91]

Lots of questions.

You should run a dynamic analysis. Model the 10ms pulse duration as a square wave. You’d also need to know the frequency of the forcing function (which is not 1/10ms). Depending on the mass of your foundation, the 74k reaction can increase non-negligibly. Sounds like a 1-DOF situation. The analysis should be fairly easy to run by hand. Grab the Chopra book for a refresher.

I don’t know what an evaporator does, beyond that “it evaporates.” With more knowledge of the equipment, you might decide that a sinusoidal pulse is more appropriate than a square pulse.

You could also make life very complicated and do an actual impact analysis whereby you define a deflection and figure stresses from there. I only suggest this because you used the word “impact,” which I don’t actually think you have.