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UEET 601

UEET 601. Learning by anticipation and participation. Earthquake: Tremor effects on man-made structures. Guitar Body Vibration. Assume a Guitar String. Guitar Body Vibration. Assume a Guitar String. Guitar Vibration. Similar to a free structure beam If we anchor the beam

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UEET 601

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  1. UEET 601

  2. Learning by anticipation and participation

  3. Earthquake: Tremor effects on man-made structures

  4. Guitar Body Vibration

  5. Assume a Guitar String

  6. Guitar Body Vibration

  7. Assume a Guitar String

  8. Guitar Vibration • Similar to a free structure beam • If we anchor the beam • Big guitar string

  9. Vibration Basics

  10. Tension of the string • Mass of the string • Length of string

  11. Assume any String • How can we reduce the vibration of string?

  12. Vibration Surface

  13. Vibration Beam

  14. Vibration Damping • Decrease vibration energy • Size of radiating surface • Mass • Absorption of energy

  15. A1 A2 A3 A4 Rigid Surface Area AT Rigid Construction: Increase Mass

  16. Energy Absorption: Damping • Opposite reaction

  17. Assume any Building • How can we reduce the impact of an earthquake on a building?

  18. Taipei 101 building • Damping • 730 Tons

  19. Transamerica Pyramid • Build on Rollers • Why would rollers be effective?

  20. Home Fire Hazards

  21. Physics of Fire • Fire rectangle • Flash point • Lowest temperature to ignite • LEL vs. UEL • Lowest concentration in air for ignition • Fuel Rich Ignition Source Fuel Oxygen/Air Chain reaction (free radicals)

  22. Make a Landslide

  23. Physics of Surfaces Slippery?

  24. Surfaces and the Coefficient of Friction • Friction results when one body contacts another • Frictional force is tangent to the contact surface that resists motion • No motion; static friction • Motion: kinetic friction

  25. Friction Formula • F = uN • Where F = Force (lbs) u = Coefficient of friction N = the force acting on the normal (perpendicular) to the surface

  26. Friction Formula: Example 1 • On a horizontal surface the normal force (N) is equal to the weight of the object N = 200 lbs 200 lbs

  27. 200 lbs Example 2How much force is required to move a 200 lbs box if the coefficient of friction is 0.75? • Recall F = uN F = 0.75 x 200 lbs F = 150 lbs

  28. Friction Formula (continued) • On a incline plane, the normal force (N) is equal to the weight of the object times the cosine of the angle with respect to the horizontal 200 lbs

  29. Example 3:Assume a 200 pound box rests on an incline plane of 20o. What is the resultant normal force?

  30. 200 lbs A = 20 O • N = W x Cosine A • = 200 LBS X Cosine 20 O = 200 LBS X 0.94 • = 188 lbs

  31. Example 5How much force is required to move a 200 lbs box up an incline plane of 20o if the coefficient of friction is 0.75?

  32. Recall F = uN and N = W x Cosine A • F = u x W x Cosine A • F= 0.75 x 200 LBS X 0.94 • F = 141 lbs 200 lbs A = 20 O

  33. Example 6 How much force is required to move the box down the same incline plane?

  34. 200 lbs A= 20 O • Gravity is acting in the downward direction • G = w sin A = 200 sin 20 O = 68.4 lbs

  35. 200 lbs A= 20 O Recall • F = 141 to move box • G = 68.4 • Net = F – G • Net = 141 – 68.4 = 72.6 lbs

  36. Issues to consider in the Hardening of Targets

  37. Supply/Return: Normal Operation Supply/Return: Pressurized Stairwell

  38. Ventilation

  39. Equilibrium recall Buildup at equilibrium

  40. Time to Equilibrium Recall Rearrange 1 Rearrange 2

  41. Recall Solve for t C = 0 at t = 0

  42. Recall Recall at Equilibrium Substitute

  43. Substituting and solving • Q = Air changes per hour design i.e., 4 for comfort • At 4 AC/hr • Q = 4V/hr • Q = V/15 min.

  44. Time to Equilibrium Solving

  45. Purging (G=0): • Vdc = G dt - QCdtbecomes • Vdc = - QCdt

  46. Purging (continued)

  47. Purging (continued)

  48. Purging Example • Assume there was a chemical release in a building • Building engineer states that the ventilation rate on full exhaust is 4 air changes per hour • Air changes per hour design i.e., 6, or 4 or 2 for comfort

  49. Purging Example • We want to purge to eliminate 99% of the toxic agent, or

  50. Purging Example

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