Stripping press foundation loads 1

[tvar]

I am a civil engineer looking at a 300 ton stripping press foundation that has failed twice before and is failing again. The client gave us the wt. of the press as 45 tons but no other additional loading. They designed the press themselves. It looks like the foundation and the two previous repairs were based on the 45 ton dead or static load only. I believe there are two other factors causing the problem the dynamic load when the press is operating and fatigue. The press has about 4500 cycles per week, I believe the foundation would have failed immediately if this wasn't a factor. Now my question, is there a way to estimate what the dynamic load for the press during operation? Is it a pecentage of the dead load of the machine or the capacity? Thanks

 

[BigH]

Why not go back to the manufacturer of the press and find out? They should have this information. Is your foundation at least 3x to even 5x the dead weight mass of teh press? These are typical "old rule of thumb" sizings for foundations. You might want to look in Richart Hall and Woods text on Soil Dynamics or Barkan's book for design of machine foundations - also Arya (Spelling??).

 

[budt]

Is this an Anode Stripping Press? There is one locally that has such a high shock level, when it strips some of the anodes, that you can hear it almost a block away and can feel it on your feet 30-60 feet away.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[hokie66]

It may help if you can you describe the type foundation and how it failed. Fatigue is not usually a factor in reinforced concrete design.

 

[tvar]

To answer the 3 responses:
The owner designed the press and doesn't have any loads other than the dead wt. of the machine. (45 tons) Foundation is under sized for the rule of thumb. It has been operating for about 30 years. The pier that failed has failed twice before and been repaired by others.
It is an anode stripping press. I am going to use twice the static load for the dynamic load, so the total load would be 45 ton static plus 90 ton dynamic.
I believe that fatigue may be a problem. There are 4500 cycles/week with the last repair made in 2003. I think the pier would have shown signs of distress sooner if it wasn't a "fatigue" problem. They only had 3/4" hooked anchor bolts which typically aren't used if there is tension. I think they should have used larger headed anchos bolts that were pre-tensioned to alleviate any type of rebound from the press cycles.

 

[hokie66]

When you say a pier failed, that could mean several things. When structural engineers talk about piers, we normally mean bored piles, but I am just guessing that you are talking about a short column or plinth which sits on a footing. If that is the case, then you are not actually saying this was a foundation failure, but rather a failure of one structural element. A better description of the failure would help.