1 / 14

Why Structures Fail

Why Structures Fail. An Introduction to engineering analysis . Building a Tower. Each team will design a tower made of balsa sticks Each team will do a structural analysis of their tower to predict where it will fail Each tower will under go ‘destructive testing’.

barb
Download Presentation

Why Structures Fail

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Why Structures Fail An Introduction to engineering analysis

  2. Building a Tower • Each team will design a tower made of balsa sticks • Each team will do a structural analysis of their tower to predict where it will fail • Each tower will under go ‘destructive testing’

  3. The Language of Engineers Mass Position Velocity Acceleration Force Pressure Stress Deformation System Failure

  4. Mass • A measure of how much matter an object is made of • Does not change with environment Metric Unit: ? English Unit: Pounds (lb or lbm) Grams (g) Weight: (in pounds force) 200 lbf 90 kg 200 lbm 90 kg 200 lbm Weight: 33 lbf

  5. Position Metric Unit: Meters (m) English Unit: Feet (ft) • Position fully defines an object’s location in space (X, Y, Z) = (.2 m, .5 m, .6 m) (X, Y, Z) = (1 m, .3 m, .4 m) Y Z (X, Y, Z) = (.5 m, .1 m, .2 m) X

  6. Velocity • Velocity describes the rate of change of an object’s position 30 m/s Metric Unit: Meters per second (m/s) English Unit: Feet per second (ft/s) • Includes both a magnitude and direction 30 m/s 10 m/s • Can also be expressed as a ‘vector’ • (x,y) = (3 m/s, 4 m/s) 4 m/s 3 m/s

  7. Acceleration • Acceleration describes the rate of change of an object’s velocity Metric Unit: m/s/s (m/s2) English Unit: ft/s2 V = 10 m/s a = 0 m/s2 V = 10 m/s 1 sec 0 sec 2 sec 3 sec 4 sec 5 sec 0m 10m 50m 20m 30m 40m 0 sec 3 sec 1 sec 2 sec V = 10 m/s V = ? 16 m/s a = 2 m/s2

  8. Force • Any influence that causes an object to change speed, direction, or shape • Force = mass * acceleration F = m*a m = 90 kg a = 9.81 m/s2 m*a = 883 N Metric Unit: Newton (N) English Unit: Pounds Force (lbf) a = 5 m/s2 F = 500 N 100 kg

  9. Pressure • When a force is exerted over a defined area • Pressure = Force / Area P = F / A Metric Unit: Pascals (Pa) English Unit: Pounds per square inch (PSI) Force = 500 lbf 24 inches 24 inches Area = 24 in x 24 in = 576 in2 P = 500 lbs / 576 in2 = .87 PSI

  10. Stress • A measure of the internal forces acting on a deformable structure Metric Unit: Pascals (Pa) English Unit: Pounds per square inch (PSI) F = 5000 kg * 9.81 m/s2 = 49050 N F = 883 N 20 m 20 m 20 m * 20 m = 400 m2 Stress = P = 49050 N / 400 m2 = 122 Pascals Stress = P = 883 N / 400 m2 = 2.2 Pascals

  11. Stress • Types of stresses Tension Compression Shear

  12. Deformation • Occurs when the stress in an object exceeds the yield strength of the material 500 kPa Material: Purple Block Yield Strength: 1000 kPa Stressed 1200 kPa kPa = kilo-pascal Or 1000 pascals Deformation!

  13. System Failure • Occurs when the stress in an object exceeds its ultimate strength (Compressive or Tensile) 500 PSI Material: Purple Block Yield Strength: 1000 PSI Ultimate Strength: 2000 PSI Stressed 1200 PSI Deformation 2500 PSI System Failure!

  14. Tower Failure • Next Week: Where will your tower fail? Boom!

More Related