Petroski uses as his primary subject the Hyatt Regency Walkway which collapsed in Kansas City 31 years ago today, but his insights extend with just as much poignancy to today. They also extend to other engineering examples including reference to the famous Tacoma Narrow Bridge collapse in 1940 (see above). The concepts he identifies are core curriculum for any engineer…
- “Designers often try to build into their structures what are known as alternate load paths to accommodate the rerouted traffic or stress and strain when any one load path becomes unavailable for whatever reason. When alternate load paths cannot take the extra traffic or do not even exist, catastrophic failures can occur.”
- “Since cracks in pipes may not be detected during inspections or tests, and since crack propagation by fatigue cannot be ruled out, [nuclear] reactor designers have devised a safety concept known as the ‘leak-before-break’ criterion against which to test their designs. If a certain type of ductile steel is used for the pipe wall, any crack that develops will grow faster through the wall of the pipe that in any other direction. This ensures that a crack will cause a relatively small but detectable leak well before a dangerously long crack can develop parallel to the weld seam and lead to a catastrophic rupture of the pipe.”
Just as compelling as his embracing failure tactices is his characterisation of the role of engineers in the world as artists as transparently exposed as soloist on stage…
- “No one wants to learn by mistakes, but we cannot learn enough from success to go beyond the state of the art. Contrary to their popular characterization as intellectual conservatives, engineers are really among the avant-garde.”
- “The engineer no less than the poet sees the faults in his creations, and he learns more from his mistakes and those of other than he does from all the masterpieces created by himself and his peers.”
- “The great liability of the engineer compared to men of other professions is that his works are out in the open here all can see them. His acts, step by step, are in hard substance. He cannot bury his mistakes in the grave like doctors. He cannot argue them into thin air or blame the judge like the lawyers. He cannot, like the architects, cover his failures with trees and vines. He cannot, like politicians, screen his shortcomings by blaming his opponents and hope that people will forget. The engineer simply cannot deny that he did it. If his works do not work, he is damned.”
Embrace the failure in any design to avert its cataclysmic downsides.