What is structural technology? What comes to mind when you hear the word “structure”?

1. U3j - L1 April 27, 2011 DRILL • What is structural technology? • What comes to mind when you hear the word “structure”?

2. U3j - L1 CORE TECHNOLOGIES Structural Technology • The technology of putting mechanical parts and materials together to create supports, containers, shelters, connectors, and functional shapes. • Example applications: • Legs on a chair, • City water tower, • Swimming pool, • Roadways and Bridges, • Bicycle spokes • Airplane wing, • Satellite antenna disc.

3. U3j - L1 Structural Technology Structural engineers are responsible for structural integrity. • Structural failures do not occur very often, but when they do, we hear about it: • Tacoma Narrows bridge (1940) • Challenger Space Shuttle (1986) • Columbia Space Shuttle (2003) • Chernobyl Nuclear Reactor (1986) • 2007 Missouri bridge collapse • As late as 1870’s and 1880’s, 25 bridges a year collapsed on the American roadways. • Many people can be killed when engineered structures fail.

4. U3j - L1 Structural Technology Almost everything is a structure of some kind: Humans Plants Animals Houses Vehicles Tables Bottles

5. U3j - L1 The “First Modern Engineer” • Galileo Galilei (1564 – 1642) • The “Father of Modern Physics” • The “Father of Modern Science” • Research into the strengths of materials • Prior to Galileo, the size and shape of most structures was determined by the traditions and rules of highly skilled craftsmen.

6. U3j - L1 Structural Technology • Structural designs advanced by trial and error until modern engineers were able to anticipate the characteristics of new buildings, bridges, and other structures. • Engineers apply science and mathematics to the problem of designing safe structures. • Many engineering principles are based on common sense.

7. U3j - L1 Structural Technology • Newton’s 3 Laws of Motion: • Inertia: objects at rest stay at rest; • objects in motion stay in motion • F = ma: Force equals mass times acceleration • Action/Reaction: for every action there is an equal and opposite reaction

8. U3j - L1 Structural Technology • Another way to look at it: • How much do you weigh? • You are pushing down on the earth that amount of force. • The earth is pushing up on you with an equal amount. • What would happen if the earth were pushing up with more force? • Less force?

9. U3j – L1 Strength of Materials • Strength of a construction material is the capacity to support loads by resisting the 4 structural forces. • Strength depends on materials’: • Type • Size • Shape • Placement

10. U3j - L1 Structural Forces • Four types of force exert stress on building materials: • Compression – push; tends to flatten/buckle • Tension – pull; tends to stretch • Shear – slide; material fractures • Torsion – twist; twist out of shape or fracture

11. U3j - L1 Structural Forces Tension

12. U3j - L1 Structural Forces Compression

13. U3j - L1 Structural Forces Torsion

14. U3j - L1 Structural Forces Shear

15. U3j - L1 Structural Forces Compression Tension

16. U3j - L1 Strength of Materials • Is bending one of the structural forces? • Deflection – bending that results from both tension and compression acting on a member at the same time. • Vertical • Horizontal COMPRESSION TENSION COMPRESSION TENSION

17. U3j - L1 Strength of Materials • No deflection

18. U3j - L1 Structural Forces • A structure must contend with two types of loads: • Dead Loads: permanent loads that do not change. • The weight of building materials and permanently installed components: • Lumber, brick, glass, nails, steel beams, concrete • Live Loads: the weight of all moveable objects, such as people and furniture in a house, vehicles on a bridge. • Includes weight of snow, ice, dead leaves, and force of winds. • The total weight or mass of all live and dead loads is the Total Load.

19. U3j - L1 Structural Forces • A building supports the following loads in the middle of winter: • 10,000 lbs of lumber • 1000 lbs. of snow and ice • 40,000 lbs of brick • 300 lbs of wind • 600 lbs of glass • 200 lbs of nails • Calculate the Live Load. • Calculate the Dead Load. Live Load: 1000 lbs. + 300 lbs. 1,300 lbs. Dead Load: 10,000 lbs. 40,000 lbs. 600 lbs. + 200 lbs. 50,800 lbs.

20. U3j - L1 Structural Forces • Live Load = 1,300 lbs. • Dead Load = 50,800 lbs. • Calculate the Total Load: • Total Load = Live + Dead Load • = 1,300 lbs. + 50,800 lbs. • Total Load = 52,100 lbs.

21. U3j - L1 Classwork • Pick four pieces of technology that have a structure. • For each structure, describe if the members of the structure are designed for compression, tension, torsion, or shear or some combination of the four.