Henry Petroski's
Interrelationship of Success and Failure
in Mechanical and Structural Engineering Design

Henry Petroski is a prolific author and major contributor to engineering design philosophy and in setting out the nature of mechanical and structural engineering.


In his first book [Petroski, 1985], he notes that engineering is a human endeavor and as such is subject to the same fallibilitys. His theory sets out why structural problems occur, when designing a structure that has not existed before.

He notes that engineering is a hypothesis. Engineers strive to design so that there is no failure.  To do this, engineers follow sound conventions and standards. When designs of structures move past what has worked well in the past, there will be a small residual probability of failure that only time can uncover. Failures need not be catastrophic because designs can ensure that early signs of failure are caught. The theory notes that there is an ebb and flow in design innovativeness. After a failure, standards and conventions are re-examined to incorporate the lessons so that the event will not happen again and that designs become more conservative. Over time, as more structures are designed using a new feature or technique, a greater confidence arises again.

The theory recommends that instead of having a list of what could fail, engineers should focus on what needs to be done to prevent structural failures i.e. communications and organisation, inspection, good quality design, structural drawings, selection of good designers, timely dissemination of technical data.

Henry Petroski notes that experience is the greatest tool: "The well prepared engineer can and does build beyond experience without hubris as surely as a well trained pole vaulter goes after a new record"


Henry Petroski

To Engineer is Human - The Role of Failure in Successful Design
St. Martin's Press/New York, 1985
ISBN 0-312-8060-9