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Elephant Enclosures

Elephant Enclosures

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.


RE: Elephant Enclosures

I'm going to assume something like this is akin to bollard design. It's more a deterrent. I'm sure if an elephant wanted to destroy whatever it's holding structure is made of, it would.

RE: Elephant Enclosures

Why is it being re-designed? Is there some reason why the current enclosure is not working? I assume you cannot simply replace to match existing. We are talking about huge elephants, right? The 10' post spacing and 4 cables does not look like a very imposing barrier with an elephant standing next to it. Not sure what your cable arrangement or spacing is, but it seems like the elephant could simply put his foot on one or more of the cables and cause the two supporting posts to tilt toward each other. I have seen two different elephant enclosures: a very high barrier wall with a viewing platform near the top of the wall, and a "moat" around the elephant area that is deep enough and wide enough to discourage the elephants from crossing it.

RE: Elephant Enclosures

Have you checked with local zoos?

Woodland Park Zoo in Seattle had a similar enclosure barrier, but the exhibit has been closed as the elephants were transferred to another facility some years ago.

City of Tacoma did too before Cindy died....

Still might have something in their records...

Mike McCann, PE, SE (WA)

RE: Elephant Enclosures

Thank you for the notes everyone.

MotorCity - There are no issues with the current barrier function, but they are developing a new layout for the entire zoo and want to modernize the look a little and think they existing posts and foundations are "way over designed". Of course, this is a common statement from non-engineers, so I am not worried about that. I would just like some type of criteria for what is acceptable for loading, deflection, etc. to develop a good understanding of the final purpose of the enclosure.

Additionally, the top cable will be electrified.

RE: Elephant Enclosures

I cannot assist directly, however, for those "non-engineer" Monday-morning quarter-back types: Several years ago my brother re-constructed an elephant enclosure that had previously failed and caused a serious injury to the keeper. The bollards were ok, as such, but it ripped and overturned the whole footing system (very stout shallow footings). The keeper sustained life-long injuries.

The zoo was Taronga Zoo in Sydney, Australia. My memory is not too clear on the details, but the re-build generally consisted of a huge, thick RC mat foundation.

RE: Elephant Enclosures

I'd like to see the client provide the design criteria to you, even if that means procuring them from another consultant. If people safety is part of this, it's a fair bit of liability for you to assume on something that's really difficult to quantify. I remember a thread a while back where somebody was designing CMU barrier walls within a barn for horse stalls and trying to design them for horse-kick impact loads. That's the only related info that comes to mind.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Elephant Enclosures


That was easy. "horse kick" narrowed the search down in a hurry which, I suppose, is unsurprising. There's even a research paper in there. Not sure elephants actually kick things though. And a raging stamped would seem to be of greater concern.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Elephant Enclosures

Back around 2004, The Texas Transportation Institute did some testing for the State Department on embassy protection barriers. I believe their test load was a 24,000 lb truck at 55 mph, which might be a little overdesigned for this application. I'm bringing it up because they had some architecturally pleasing barricades that may appeal to the zoo.

I recall the test engineer saying it was a big change from their usual work crash testing highway barrier. FHWA is very concerned about occupant protection, but the State Department didn't much care.

RE: Elephant Enclosures

When we have done this in the past we received design loads from the client. I would ask them first.

RE: Elephant Enclosures

RE: Elephant Enclosures

IRstuff: I came across a couple of those references as well with some valuable information. I did come across a reference that mentions a 14,000 lb elephant traveling at 20 mph. I guess I will proceed with checking the loading capacity of the cables and the concrete filled steel tube based on that loading criteria. It appears that overturning of the foundation is going to be a pretty significant issue at that loading...

RE: Elephant Enclosures

Could become a 'scratching' post, too...


RE: Elephant Enclosures

I have the same question from a client. The client was able to show me pictures of a corral under construction. Client thought the fence was 5" Sch. 80 pipe on 24" centers with 2x5 tube at top to keep alignment. Height was 7'.

I considered using a human guardrail as a example and scaling it up. Current US male average is 5'-9" tall and weighs 195#.
A 42" guardrail is 60% of that height and is required to carry a 200# load (100% of weight) in any direction.

Scaling up to an 11' tall elephant at 13,000#, you come to a 6.6' tall rail with a 13,000" load at top.
With a spreader at the top to carry the load over 3 posts at 7' height, that calculates to a 6" Sch. 80, 50 ksi pipe.

Does this sound realistic?

RE: Elephant Enclosures

Bill A.,

What if the elephant wants out? Are regular railings designed to withstand deliberate destruction by humans?


RE: Elephant Enclosures

It still comes back to a lack of data. I am down to calling zoos that have elephant exhibits and asking questions.

RE: Elephant Enclosures

Just a quick update: Due to my lack of confidence in designing what the original post was describing, we have kicked the design back to the Zoo who has hired another structural engineer familiar with zoo design. I have asked to see the design criteria that that they are using for future reference, but have not heard back yet.

I stated a little earlier that I found something indicating that you need to account for the max speed of the elephant running into the enclosure, which is approximately 20 mph depending on the type of elephant. This obviously increases the loading significantly if indeed it needs to be accounted for in that manner.

Bill A - Please keep us updated if you find out any valuable information from contacting the zoos.

RE: Elephant Enclosures

Regarding loads- Yes, Force = Mass x Acceleration, with a differential for time. Back to the no accurate data. How fast can an 13,000# elephant accelerate?
I need to call Rich Purnell in Astrodynamics.

RE: Elephant Enclosures

It has been a long time since I have cracked a physics book, but the way I see it, the impact force should be independent of an elephant's acceleration (unless you are going to limit the traveling speed based on available "speed-up" space). If a 13000# elephant is traveling at 20 mph towards your fence, I don't care if it happens to put on the brakes just before impact (negative acceleration) or is still gaining speed (positive acceleration). The fence will see roughly the same force either way.

If you are looking for traditional physics equations to apply you might look at something like 1/2 M V^2. Also make sure you consider slowdown distance in your analysis.

RE: Elephant Enclosures

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).

RE: Elephant Enclosures

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.

RE: Elephant Enclosures

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.,:


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.

RE: Elephant Enclosures

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.

RE: Elephant Enclosures


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

RE: Elephant Enclosures

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.

RE: Elephant Enclosures

And a return high five to you, sir![wavey3]

RE: Elephant Enclosures

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".

RE: Elephant Enclosures

This is more what the client has in mind.

RE: Elephant Enclosures

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.

RE: Elephant Enclosures

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.


RE: Elephant Enclosures

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."

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.

RE: Elephant Enclosures

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.

RE: Elephant Enclosures

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, wait. ok bad example

RE: Elephant Enclosures

Quote (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.

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.


RE: Elephant Enclosures

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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Elephant Enclosures

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!

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