Petroski Notes
Not ready yet!
Random bits about the book "To Forgive Design" 2012 by Henry Petroski, and related ideas.
Book Notes
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Reliability and failure in chip design
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Abusing statistical distributions
Nicholas Taleb's book "The Black Swan".
Bart Kosko's book "Noise".
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Vintage Tektronix oscilloscopes
In the 50's through the 70's, Tektronix designed oscilloscopes to last a very long time. Some have, and are displayed at the Vintage Tek museum, between Beaverton and Portland. Normal museum hours are Friday and Saturday, but I imagine that special hours could be arranged for visiting dignitaries.
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Robert Courland's "Concrete Planet"
I would love to see a review by a concrete engineer - this seemed a little "selective". Book notes here
Cathodic protection of rebar
Concrete Planet makes much of the rusting of rebar in old concrete structures, and the trillions of dollars that may be necessary to replace thousands of them in the near future. I don't know how real the problem is. If it indeed a serious problem, we ought to be looking for ways to slow or stop this decay.
Rebar iron won't oxidize nearly as fast if it is biased cathodically. Too much voltage, and the electrode will emit hydrogen, which can embrittle the iron. Without knowing the voltage drop through the concrete, it is difficult to bias the iron properly.
A proposed invention
I'm releasing this idea into the public domain. If it makes sense, please use it to protect America's aging reinforced concrete, saving lives and tax dollars. Perhaps a joint project between the CE and ME departments at Duke could get some papers out of it. I can imagine this turning into a little circuit board with a solar cell, a battery, and a small integrated circuit with a simple bluetooth radio transceiver for status logging and bias calibration, mass produced and added by the millions to reinforced concrete structures.
If you live in a place like Oregon with lots of rain and humidity, and have cheap telephone jacks with inadequate gold plating, you've listened to anodic oxidation of copper - it makes a hissing noise, which I presume are the little electrochemical events of copper ions oxidizing, adding up to electrical noise.
I presume the current drawn from a cathodic bias circuit at too low a voltage will make a similar noise. If the current is detected with a "virtual ground" amplifier, the capacitance of a few hundred feet of rebar can be nulled, and the wideband noise measured.
I also presume that hydrogen generation is a higher energy phenomena, and has a different noise spectrum. So proper bias on a rebar electrode will be between the "copper oxidation hiss" and the "hydrogen hiss". It would be instructive to digitize the electronic spectrum of a piece of rebar in concrete as a function of voltage, and see if these hisses can indeed be distinguished, and a bias point chosen for the optimum tradeoff between hydrogen and oxidation, perhaps even slowly varying the voltage to alternate between the phenomena, reducing the briefly oxidized iron.
I do not know how well this would work for really large expanses of tied rebar - chances are there will be DC voltage gradients across the structure, so some portions of the electrode will be oxidizing while others will be reducing. While this technique might still help prolong the lifetime of existing reinforced concrete, it will probably work best on rebar electrodes carefully designed to match areas of similar ambient electrical potential and long term water infiltration and pH changes. So new designs will eventually get finite element electric field analysis, as well as mechanical analysis.
It may also be possible to find patches of damaged rebar by using large electrode plates on the surface of the structure to change the electric fields, and look at spectrum changes. Perhaps external patch electrodes could be added to parts of an existing structure's surface to remediate or stop damage. Ugly, but not as ugly as a bridge collapsed into a river.