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The bridge across Avon Gorge

Thu 12 Nov 2020 by mskala Tags used: ,

The question has come up of building a bridge across the Avon Gorge. Davies, who manages the funds, says the project must be abandoned because it is technically impossible. Isambard, the engineer, says it can be done.

Clifton Suspension Bridge

Davies says that the stones of the bridge would lack the necessary compression strength. Isambard carefully explains that tensile strength is more relevant than compression in a suspension bridge of the type contemplated, and the current state of the art in wrought-iron chains and similar bridge components, provides more than enough of both.

Davies says the bridge's weight would require a central support tower, which would interfere with navigation on the river below. Isambard sketches his calculations of the forces involved and how they can be transferred to the ends of the bridge without a central tower.

Davies says that wind-driven vortex shedding would set up a resonant vibration in the roadbed that would lead to premature catastrophic failure. Isambard talks about nonlinear differential equations until Davies cuts him off, saying, "That's not the point!"

Davies says that if the Earth's gravity should suddenly reverse polarity, the whole bridge would float off into the aether, and then where would we be? Isambard cannot quite believe his ears, and falters "Um... gravity just doesn't work like that."

What the Hell is going on here?

Davies has some other reason - not technical possibility of building the bridge, at all - for vetoing the bridge project. He may consciously know what his reason is and just not want to discuss it, but it's also quite possible that he is not consciously aware of the reason and he only consciously knows that the bridge must not be built even if it can be built. Either way, each of his technical objections is for him not only a reason the bridge can't be built, but also a reason that the discussion must end.

At this point Davies thinks Isambard is either stupid or malicious, repeatedly trying to continue the discussion after Davies made it abundently clear that the discussion had to end.

Isambard's entire job is to solve technical problems. Davies is in fact paying him a lot of money for that service. When presented with an obstacle like weak building materials, it is both his obligation and a matter of personal honour that he must evaluate whether the obstacle exists in the first place, if so whether it is surmountable, and to find a way over it if the obstacle and the way over it both exist. When his employer presents him with a technical issue, that's an order to address the issue, and to not walk away from the discussion until the matter is settled.

At this point Isambard thinks Davies may be both stupid and insane. Davies gave Isambard a series of orders that made less and less sense, and then got angrier and angrier the better Isambard did his job of obeying those orders, solving the problems, and especially, continuing the discussion.

It's likely that the employment relationship will end, either by Davies firing Isambard or Isambard quitting, after even one episode of this script. If not the first time, it will happen after the second or third repetition.

I've seen it happen many times, both as a participant and an uninvolved observer, and I think it's quite familiar to anyone who has worked in a technical discipline.


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