The Legend of Thomas Telford

Understanding the Bathtub Curve

The distinction between a civil and military engineer is a recent one that was first attributed to Thomas Telford, the Colossus of Roads. The man that initially built out Great Britain’s road infrastructure in the 18th century. Without Telford having linked up Great Britain, by connecting its roads, it would have been impossible for James Watt to create the steam engine, without which, the industrial revolution would not have taken place. The important lesson here is that electricity supply depends on reliable transport infrastructure being in place. Roads and Railways that are natural monopolies, are a necessary investment for any country that wants to bring opportunity to its population and that is why in most countries today, their maintenance, supply and expansion remains the responsibility of the state. In locations where they have been privatized, investors quickly realize that there is no return on investing in long term infrastructure and they are either reabsorbed by the state or led to collapse as was tragically the case of South Africa’s Railways. When it comes to infrastructure, it’s absurd to think that there is no case for government control or expansion that is to say, nationalization.

Telford was an impatient figure, had little tolerance for error, mathematicians, or structural engineers who would fine tune their cross sections, because their clients told them to “save costs”. Had he lived today he probably would have chased environmentalists and their lawyers of his building sites for deliberately delaying the projects, as he knew that it would result in people not having clean food or drinking water.

Telford knew he could do it, because he had the respect of the workers on his side. He was not afraid to get his boots dirty and jump in with them. Telford also instinctively knew about the law of entropy and decay, that eventually all structures, roads, dams, bridges and even nuclear power stations, eventually would come to an end. Which is why if you don’t maintain them , extend their life time or plan for their replacement, it will be a costly societal mistake.

Fatigue

The fatigue mechanism is easy to understand. Structural Engineers know that all building materials suffer from cycle stress failure as it is subjected to up and down loads throughout their life. We try and push failure in the future is by adding a safety factor. But eventually the margin runs out as cycle failure sets in as the mean stress approaches with time.

The law of entropy is the limiting factor before any structure snaps.

Large projects engineers often use the Bathtub curve to try and predict fatigue failure. Understanding the Bathtub Curve is key for anyone interested in infrastructure, as the problems in the design of any project is only picked up towards the latter end the curve, which is why the famous saying goes that “doctors bury their mistakes, but if you don’t listen to old and wise civil engineers, then their mistakes will bury you”.