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31 May 2016

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Jenny

This incident reminds me of the bridge failure in Minneapolis a few years ago. Until the flaw in design tragically showed itself, the bridge was thought to be safe.

Meredith

I like your insights. I just chaperoned a zoo field trip with a special ed class of 15 children ages 3-5, half of whom have delays developing impulse control. Guess what? We weren't even told to hold their hands. Why? This is part of learning how to operate in the world, practicing the skills they have learned in a slightly-less-controlled setting. There is more risk in non-familial adults touching children than there is in walking an arms length away in a zoo, which is widely considered to be a safe place designed for children.

bearing

Jenny, I know too little about the zoo enclosure and too much about the Mpls bridge to draw that analogy yet.

In the case of the I-35W Mississippi bridge, the gusset plates that failed had been undersized relative to the standards of the time -- it was an overlooked error, but a true error. Also, years of inspections failed to bring it to light, apparently with some degree of negligence. The bridge didn't fall for many years because of the many redundant safety factors that are built in, but over the years those were compromised as the bridge carried heavier loads -- and was finally compromised by the construction project that was underway at the time of the collapse.

The years that went by without a breach in the gorilla exhibit in Cincinnati can probably be attributed in part to the series of redundant barriers, but it's worth pointing out that the barriers are largely psychological ones. A fence, easily scaled or penetrated. Some shrubbery. A steep drop down to the animal area, which is only a barrier if you are afraid of falling. Probably some signs saying "Don't." The control of parents and chaperones over children and of adults over themselves.

I don't know whether those barriers were designed in accord with accepted standards of practice (I am not sure what the standard-setting body is, but I suspect it is the AZA). I don't know whether the barriers were regularly inspected to see if they were in good repair, whether they were regularly considered to see if they had fallen behind current standards of practice, whether any new circumstances had come up that "increased the load" in a predictable way on any of them (are mixed crowds more distracted and unruly than they were in 1978? is this bridge carrying more traffic than its designers expected?)

In short, there was real negligence involved in the I-35W collapse, at least if the investigation outcome is to be believed. It may well be that there is in the zoo enclosure design, but we won't know that for a while.

Christy P.

Here's a perspective I haven't noticed yet in the conversation (although I have read little about this incident since it happened when I was off grid), why didn't any other adult attempt to retrieve the child in the time between scaling the fence and going over the edge? Are we so afraid of Someone being upset that we interacted inappropriately with his/her child that we (collective adults and older children) are willing to stand by when a young child is putting himself at risk? I will say that I've been that person. I've snagged a child that I didn't birth (because I just can't say, a child who is not mine here - the point is that they are ALL ours) from running across a parking lot while the mother loaded groceries in the car. I've helped a little guy down who climbed too high at the playground while his oblivious parent clicked on a device. Sometimes that behavior, what I considered a kindness for the child, has gone poorly for me. The parent, likely embarrassed, spoke roughly to me about keeping my hands off the child. I can take it. I saw a need and acted according to my values. This world is fast and exciting and screaming for kids to explore it, but many aspects are just not safe for free exploration. Drivers can't see them. Things that are clearly fences to adults because of context look like playground structures to kids. Kids can't see over edge-planted shrubbery to notice the drop and moat below. If I were looking to assign fault it would be to every competent person near that exhibit who saw the boy heading for trouble and did nothing.

bearing

You know, you're right, Christy. I haven't seen anybody mention whether there was time for bystanders to notice and react.

Jenny

I would definitely rely on your understanding of the bridge collapse rather than mine. My father talked and worried about it a lot, but that's not to say I fully understood what he was talking about. I thought the plates were thought, at the time of construction, to be sufficient, but I could be misremembering what he said.

It was my impression from that one Facebook post that when the crowd tried to react to him after he crossed the shrubs, but before he dropped into the moat, the boy responded by basically jumping.

Christy P.

A comment about design -- why aren't there more raised viewing areas or integrated stepstools in places theoretically designed for children?

bearing

Yeah -- it would have to be better to have a designed "climb up and see better" spot than to have people lifting their kids above the rails to see.

The Minnesota Zoo has numerous benches and step-up curbs near the glass in glassed-in enclosures. It's a nice touch. I don't wind up lifting kids much at all (not counting the youngest in the back carrier). I can't remember if that's so near the open-air enclosures.

Jenny

I asked Daddy about the bridge failure last night. You are right about the plates being undersized.

His words: They missed the obvious that a third year engineering student could have caught.

But this was the part I was remembering and got confused with the plates. The bridge design had no redundancy. If the primary load path failed, the bridge failed.

The collapse triggered a flurry of inspections of bridges with the same design and non-redundant designs have fallen out of favor.

Anyway, I've gone far afield of gorillas and toddlers.

bearing

He's right -- I shouldn't have said "redundancies" but "safety factors."

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