Well it’s that time of year for academics (at least those on a semester system) when we begin another term of teaching and learning. This Fall I am somewhat officially retired from full-time teaching (if the university had started me sooner it would be official) but I am back teaching my Foundations course.
Towards the end of that course I get into a topic that is relatively new in engineering: Load and Resistance Factor Design (LRFD.) LRFD is a fancy technique that attempts to quantify uncertainty in both the way structures are loaded and how they resist that loading, Loads on civil structures include the dead weight of the structure, what the structure carries (traffic on a bridge, for example) and loads such as earthquake, wind and impact loads. The structure resists it by having material that doesn’t either break or move excessively during use, and that material ultimately includes the soil, rock or what’s in between that supports the structure.
In the past we used something called Allowable Stress Design (ASD,) which involves using factors of safety, a concept familiar to people even outside the engineering profession. Typically the literature states that we have moved from “deterministic” design (ASD) to “probabalistic” design. I don’t agree with that: we’ve always “played the odds” and built into our structures additional material to deal with uncertainties, including what one Australian engineer called a “factor of ignorance.” The difference is how we do the calculations: LRFD is supposed to be a better way of quantifying those uncertainties, although I have one colleague who disagrees with that.
In the course of teaching that, I present the following graphic.
This shows two bell curves (see, I’m already in trouble) of various loads and resistances. The idea is that the ability of a structure to resist loads and stay together/in service is greater than the loads it’s subjected to. Notice two things:
- There is no one load or resistance for a structure. There is a distribution of possible loads, which includes the fact that those loads can vary over time.
- There is always a blue shaded region where the two overlap. That’s the region where the loads can overcome the resistances. There is no way to get rid of this; we can only minimize the region.
The last point is, in the context of our society today, secular blasphemy. Why is this? Because we as Americans have been conditioned to believe that life is supposed to be perfect and without adversity. Failure to achieve this leads to most of the bile we see in the streets and on social media.
Considering the case of COVID-19, although coronaviruses have been with us for a long time, the unique characteristics of this one meant that we went into the pandemic with greater uncertainty. This meant that the “load” bell curve tended to be flatter and broader (if not in reality at least in our perception) than with other diseases. On the other hand those uncertainties extended to the way we resisted the virus, so that curve is flatter and broader too. To put it like the public health officer at our university did, our response was like building the plane while flying it at the same time.
The result of both of these is that the blue shaded overlap region is larger than we’re used to seeing. That meant that bad things happening were inevitable until our knowledge of what we were up against and how we planned to counter this were better known, the curves sharpened (and hopefully further away from each other) and the blue region shrunk. This is not an instantaneous process with any assault like this; it takes time, especially with something that is a moving target (mutations, uncertain interactions with the populations and environment, etc.)
You’d never know that from the rhetoric that comes out of our society. On the one hand we hear that, if we do such and such, the virus will completely go away. On the other we have a prosperity teaching type of denialism which tells us that these adversities are illusory. Neither of these is realistic. We can do things to improve the situation. Sometimes these things are a “breakthrough,” sometimes they are incremental. In football we can either get to the goal with one “Hail Mary” pass or we can grind from one first down to another. Anyone who has watched the game knows that, with well matched teams, the latter is more likely to succeed.
Unrealistic expectations make our society insufferable, and decrease the desire for longer life, which may explain our rising suicide rate. (There is a better way.) They’re also profoundly unscientific, and the remind us that, in spite of the gaudy rhetoric, those who run our society are profoundly unscientific as well. Our adversaries are better prepared in that regard, which doesn’t bode well for the global conflict that is shaping up.
Unhappily living with that reality is, I suppose, the price for teaching secular blasphemy.