Success and failure in engineering

Failure is a central idea in engineering. In fact, one definition of engineering might be that it is the avoidance of failure. When a device, machine, or structure is designed by an engineer, every way in which it might credibly fail must be anticipated to ensure that it is designed to function properly. The engineer ensures that these and other failures do not occur by analyzing the design on paper, and the objective of the analysis is to calculate the intensity of forces in the structure and compare them with limiting values that define failure. In a suspension bridge, for example, the total force on the main cable depends upon the geometry and material of the bridge and the traffic it must carry. The force that the cable must resist determines how large the cable must be if a certain type of steel wire is used. There also is strong evidence in the historical record that engineers and their antecedents in the crafts and trades have always pushed the envelope until failures have occurred, giving the advance of technology somewhat of an epicyclic character.