The Margin of Safety: teacher key

How Buildings Stand Up, grade 12 edition, written for 12th grade and up. No engineer can promise a tower will beat every wind. Read how margins of safety, a bamboo-inspired tube, careful concrete and one honest phone call shaped the tall buildings of today.

Read the book. Print this page for the key.

Questions and answers

1. What can engineers give a structure, since they cannot be sure it will resist every load?
   • Large enough margins of safety (answer)
   • A perfect guarantee
   • More windows
2. Why was the first skyscraper argued over?
   • Oriel Chambers already had an iron frame and glass curtain wall (answer)
   • No one kept records
   • It fell down
3. In what year did the public learn of the Citicorp repair, according to The New Yorker?
   • 1995 (answer)
   • 1977
   • 1965
4. What does the disagreement over the building code show?
   • Accounts can differ even about well-known events (answer)
   • The tower was never built
   • Code rules never change
5. As used here, what does 'turbulent' wind mean?
   • Steady and smooth
   • Cold and dry
   • Swirling and uneven (answer)

Words

• cantilever: fixed-end beam
• outriggers: core-to-wall arms
• turbulent: swirling, uneven
• ethics: right conduct