Design of Foundation for Steel Silo storing wood chips
Design of Foundation for Steel Silo storing wood chips
(OP)
Hi,
I am designing a foundation for 27meter high steel silo, 15m in diameter, full of wood chips (density of green wood chips approx. 350kg/m3). The silo is supported on a braced steel frame structure, 10 meter high on a raft foundation approx. 1.2m deep. I have sized the steel frame and raft based on the wood chip density and wind loads.
However, I was told that the silo and foundations should be designed for the density of water, in the event of fire (deluge system). This would mean that the actual weight would be 3 times more than I assumed in my design.
The ground conditions are reasonable, could get allowable bearing approx. 150 to 180kPa but if I need to assume a silo full of water this could go up to 400kpa. Also the steel tonnage will increase significantly, about twice the tonnage I have now.
I suppose my question is to anybody who has experience in designing silos for wood or similar material. Is this a common approach? Or maybe the silo should have some kind of relief pressure valves?
Thx
Karlos






RE: Design of Foundation for Steel Silo storing wood chips
BA
RE: Design of Foundation for Steel Silo storing wood chips
A couple of questions. "I was told"- is this the customer/owner telling you this is a requirement for their operation? If so, design accordingly. If it's just somebody else in the office speculating, run the idea past the owner/process designer to see if that is a realistic expection.
Do they have enough water available to actually flood the silo if they wanted to?
Is the bottom of the silo and the attached equipment actually sealed where it would hold water if they did start flooding it?
Is it the intent that if they have a fire, flood the silo, that the silo would then still be usable?
By the way, I have read of them keeping piles of coal wet at power plants to reduce the fire hazard. I have heard that bales of green hay in a big stack can generate heat and spontaneously combust. So it wouldn't be unreasonable that they would have a fire hazard there.
RE: Design of Foundation for Steel Silo storing wood chips
You might try filling a bucket with wood chips, weighing it; and then filling the bucket and chips further with water, and weighing it again. These would seam to be the extremes, and it would be unlikely that you could have a silo full of water. The chips still take up the majority of the silo volume, and even when drenched they weigh less than water. I agree with JStephen that the silo would likely drain, or should drain. In case of fire all you want is to saturate the wood chips, not to fill the tank with water.
RE: Design of Foundation for Steel Silo storing wood chips
Someone else on the design team must know what system is to be used.
Sorry, that's not much help is it.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Design of Foundation for Steel Silo storing wood chips
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Design of Foundation for Steel Silo storing wood chips
RE: Design of Foundation for Steel Silo storing wood chips