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To Engineer Is Human

Page history last edited by Chris Yeh 13 years, 9 months ago

Notes by JP Adams (www.johnpadams.com)

 

Chapter 1

1.    Engineering failure is measured in two ways: human death toll and materials lost

2.    Human death toll is extremely rare: 25 deaths a year vs. 50,000 car accidents.  Large media attention is given to engineering failures however.

3.    Material cost is high.  Fracture accounts for $100 billion annually.

 

Chapter 2

1.    Engineering progress is similar to growing up.

2.    All structures will fail due to too much use or incorrect use. 

3.    Children test the limits of systems over and over until they learn the intended purpose of structures.

 

Chapter 3

1.    The chief task of an engineer is to determine “how long it will take before cracks or the simple degredation of its materials threaten the structure’s life.”

2.    “…Fatigue is not a precisely predictable event.”

3.    Consequence of failure contributes to consumers expectations of a given device. 

 

Chapter 4

1.    The scientific method (testing hypothesis) is used in engineering development.  At times results can be less than explicit either through trial and error or luck. 

2.    “The fundamental feature of all engineering hypotheses is that they state, implicitly if not explicitly, that a designed structure will not fail if it is used as intended.”

3.    You can arrive at an answer that is qualitatively correct, but quantitatively not absolutely accurate.

 

Chapter 5

1.    Most engineers have a desire to do what has not been done before. 

2.    “As engineering began to apply the scientific method to structural problems, it moved away from purely aesthetic considerations and separated itself from architecture.” 

 

Chapter 6

1.    “Designing a bridge or any other large structure is not unlike planning a trip or a vacation” it involves a series of choices. 

2.    Which innovation leads to a successful design and which to a failure is not completely predictable.  

3.    Conservative engineers copy.  Others innovate. 

 

Chapter 7

1.    You can learn more from studying failure than from studying success.

2.    Minor failures (a crack in cement vs. a bridge collapse) can also be insightful.

 

Chapter 8

1.    The Hyatt Regency skywalks failure in Kansas City was one of the largest engineering disasters of all time: 114 people died.  200 were injured. 

2.    Failure often lies in the details as opposed to large missteps.  DC 10  airplane disaster resulted from replacing of the engine after servicing in a position unanticipated by the designer. 

3.    Studying failures offer different lessons than studying successes.  They are at least as important as successes. 

4.    How do cultures of fear develop?  For example mad rush off the Brooklyn bridge. 

 

Chapter 9

1.    A common metric in engineering is the “factor of safety”

2.    The “Factor of Safety” is calculated by dividing the load required to cause failure by the maximum load expected to act on a structure. 

3.    The “Factor of Safety” must be able to sustain all the adverse conditions occurring simultaneously

 

Chapter 10

1.    50% to 90% of all structure failures are believed to result from crack growth

2.    Often crack development progresses slowly enough that it can be recognized before failure. 

3.    Safety relies on maintenance, both mechanical and human.

 

Chapter 11

1.    The cracked frames of the NYC Grumman manufactured busses is an example of minor cracks growing into systemic problems.  It is also an example of how politics contributes to evaluating structural failure. 

 

Chapter 12

1.    The Crystal Palace, built for the first world’s fair in 1851, was a wild success.

2.    Engineering failure rates have dramatically improved with time.  In the 1850’s 25% of iron railway bridges failed. 

3.    Interesting fact: one of the key benefits to overlapping design and construction is protection against inflation.

 

Chapter 13

1.    The closest definition Petroski gets to defining the correct balance innovation and needless conservatism is: “if an inspired design relies on sound principles and does not try to extend the limits of art or engineering too far too soon, it stands a good chance of joining the canon of success.”

 

Chapter 14

1.    While failure analysis (after the fact forensic analysis) is critical to the improvement of field, its also like Monday morning quarterbacking. 

 

Chapter 15

1.    The virtues of the slide rule were two fold: limitation analysis and estimate analysis.

2.     The questions associated with usage of a new technology were moot when the calculator became cost competitive. 

3.    Other technology (like the CAD system) has a negative impact upon the engineering industry.  Mistakes are more easily made.  These devices need humans to ask the correct questions, to provide the correct scope and to install checking mechanisms.  

 

Chapter 16

1.    Creative writing has a place in analyzing engineering.

 

Chapter 17

1.    Failure proof design doesn’t exist

2.    Innovation involves risk, start by studying past failures

3.    Well prepared engineers build beyond experience without hubris

 

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