Elephant Enclosures 3

[Civ-StructEIT]

I have an odd question for everyone. Has anyone every designed an elephant enclosure? I currently have a project, where they asked us to re-design an elephant enclosure.

The only parameters that I have are that there are Concrete Filled Steel Posts, spaced at 10'-0" O.C., with (4EA) 3/4" diameter galvanized steel cables equally spaced along the posts.
Does anyone know of any design criteria resources to use for Elephant enclosures? I am having trouble finding any engineering resources for this one.

Thanks!

 

[IRstuff]

The challenge is determining the D in F = W/D, which is often a question. Typically, answers come back with making some use of strain or spring constant in the material being hit

TTFN (ta ta for now)
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[MotorCity]

RWW0002 - the impact force will always depend on the acceleration (or deceleration in the case of an object being stopped). The deceleration occurs when the moving elephant is stopped by the barrier. The change in his speed from 20 mph to 0 mph when he hits the wall is the (negative) acceleration. The real question is the duration of impact or how long does it take for the elephant to come to a complete stop (probably fractions of a second).

 

[RWW0002]

Motor - I agree. That is why I mention slowdown distance. But F=MA as mentioned by Bill makes it sound like the force exerted would be a function of the Elephant's mass and acceleration(ability) prior to impact. I apologize if I am misinterpreting your comment Bill. I only commented because this way of thought (always defaulting to F=MA) was a common mistake made by physics students for this type of problem from back in my paper-grading days.

The force should be something like (1/2MV^2)/D where D is the slowdown distance. See IRstuff post above.

 

[Archie264]

One approach to that, per IRstuff, MotorCity and RWW0002, is to do it iteratatively. That is, assume an initial d, set energy = work and solve for F. I.e.,:

Given:
E=.5mv^2
W=Fd

1. Assume an initial d, set E=W and solve for F (and watch your units)
2. Apply that F to the proposed structural system and see what deflection it yields.
3. With that knowledge refine Step 1 and repeat Step 2.
4. Repeat to the level of accuracy desired.

I've had folks tell me this is not the correct approach but it's better than asking the elephants.

 

[SwinnyGG]

I have used the following workflow to design a couple of barriers for very odd applications- I think this would get you there.

1) determine KE to be absorbed by the barrier

-You have this, since you have elephant mass and speed​

2) Make some conservative assumptions about which part of the barrier will be engaged by an impact

-example: if an elephant runs into your barrier at full speed, how many of the horizontal cables will be engaged in stopping said elephant?​

3) Determine maximum strain which can be absorbed by the engaged portion(s) of the barrier before your failure criterion is reached (elastic or ultimate limits, etc)

The result of step 3 give you the D in F=W/D; you can then determine what the various forces are, and you're on your way.

Some of these parameters need to be factored, depending on your approach and how you build in safety factor.

This process is, of course, iterative; but it's one way to get there.

 

[WARose]

On this thread, I gave some info on impact loading (including a formula from Blodgett):

http://www.eng-tips.com/viewthread.cfm?qid=431133

 

[Archie264]

LT(jg)KRI,

I think we were semaphoring our messages from adjacent ships simultaneously. Hopefully the fleet admiral won't mind.

 

[SwinnyGG]

Two posts which, for all intents and purposes, promote the same method of problem solving with the exact same time stamp.

Never seen that one before- but if anything, it serves to verify the the approach is sound ha ha.

One Internet high five for you, sir.

 

[Archie264]

And a return high five to you, sir!

 

[racookpe1978]

Getting in this a bit late, but can't you take advantage of the fact that an average elephant is smarter than the average truck. (I will resist the temptation to compare the average truck intelligence to the average *ss political party intelligence ...)

Even an enraged elephant will "bend and break things" (like its head and shoulders) and so each subsequent charge will be less than the first. Consider running lighter weight horizontal round tube steel between the 10 inch dia verticals. Each horizontal is built in an opened "U" shape so it will deflect at each hit, but the deflection absorbs the energy by buckling and yielding and bending further and further "out" (away from the corral) with each hit.

But the elephant will be hitting the hard steel horizontal each time. And the deflection of the sacrificial horizontal will require replacement, but keep the animal in. (Make the horizontals closer to the ground closer together to restrain the smaller calves and females.)

If you run the cable inside the horizontal tube steel between each vertical, through the vertical, out through the next horizontal, into the next vertical, out from that vertical into the next horizontal, you'll tie the whole fence together so the force is eventually spread out between 4 or 5 verticals, and all of the intermediate horizontals are also bending and yielding. Back it up with an alarm and intervention system so the fence doesn't have to stand continuous asault all night, but only for 5-15 minutes until an attendent/vet administers the "sleepy shot".

 

[Bill A.]

This is more what the client has in mind.

 

[racookpe1978]

Now, the other thing you can do to minimize the "collision velocity" (which for kinetic energy is Mass x v^2) you can put some simple barriers perpendicular to the longest straight run towards the final elephant barrier. Not a complete barrier, just something high enough so the running elephant has a shorter distance to accelerate, less final velocity before collision.

With that picture, you can see the thing has more than 150 straight shot at the fence.

 

[kingnero]

Had a RFQ yrs ago for a buffalo enclosure. design criteria that were given was weight and velocity of the animals. Each post should withstand a bull of a certain mass, running into it at speed. Don't remember the inbetween parts nor distance. Didn't got it, so can't help you further.

---

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[EngineeringEric]

In those photos, the first thing that comes to my mind is the elephant pulling the fence in. How much force can an elephant pull?
According to the internet "They can carry a vast weight but are very heavy. They can pull up to 9 tons - 1.7 times their normal body weight."

http://www.telegraph.co.uk/news/ear...d-by-their-power-to-weight-ratio.html?image=7

Therefore, i say design it to handle that force. The pushing power is probably equal, i wouldn't think stopping it from running into the fence is possible... plus with that 18,000# it would probably hurt the elephant if it tried.

 

[Archie264]

I don't know if they can get a running start and "punch" the wall with both front legs like my dog does with unsuspecting visitors but I wouldn't put it past them.

 

[IRstuff]

They're pretty smart; I ran across an article that said that one particular bull elephant in Africa managed to break out of his enclosure 451 times.

TTFN (ta ta for now)
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[MotorCity]

I agree, elephants are intelligent.....they mourn their dead. I don't think any intelligent animal would charge full speed into an inanimate object. That would be like an architect running full speed, face first into a block wall....er, wait. ok bad example

 

[drawoh]

They're pretty smart; I ran across an article that said that one particular bull elephant in Africa managed to break out of his enclosure 451 times.

Did he smash his way out or was there a latch he figured out? Park Rangers in North American like to claim that there is an overlap between the stupidest tourists and the smartest bears.

Running headlong into an inanimate object is a good idea if you want out, you weigh seven tons, and the object has not been properly engineered to withstand impacts.

--
JHG

 

[EdStainless]

There is an official zoological park association that has design guidelines for animal enclosures, I presume that you need to be a member to get the information.
I helped with design of a Bison pen some years ago, I believe that we ended up with 10" "I" beams driven 10' into the ground (and extending 10' above) on 36" spacing, with heavy wall 2.875 drill pipe welded horizontally every 24". Bulls would charge it at full speed, and the fence would flex a bit. If you were walking by it would scare you pretty good. Not very aesthetic, but worked.

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[Forensic74]

I actually designed one of these cable/post elephant enclosures in the midwest. The zookeepers were highly annoying to work with. On one hand they touted how the elephants could take a 6x6 steel tube and turn it into a pretzel, and then turn around and complain that the concrete filled post sizes and spaces we came up with were too stout.

My design has been in place for over 10 years and i havent yet read anything in the news about an elephant rampage!