1. PROTECTING PEOPLE AND BUILDINGS FROM TERRORISM National Academy of Sciences 2001 The recommendations in this report, originally addressed to the prudent and potentially targeted, have now assumed compelling urgency for us all. There is a host of nonintrusive changes in construction techniques, materials, and building management practices that will result in the least harm to architecture and cost, and provide the greatest good for protection.

2. The Root of The Problem Offset Resistance SOLUTIONS

3. Two Extreme Views within Engineering The NeoComp View Blast and Impact are Topics for Specialized Computation and Specialized Experts The Conservative View Blast and Impact can be handled effectively by improving details

4. Murrah Federal Building Oklahoma City 19 April 1995

8. G20 Transverse Reinforcement Spacing 16 in.

10. El Nogal Building Bogota, Colombia 7 February 2003

13. ( kip KE kip 00.10.20.30.4 0 100 200 300 400 Displacement, in. PE  ) in    Bogota, El Nogal

14. The Facts Murrah Bldg Column Fails BOGOTA Demand OKLAHOMA Demand El Nogal Column Survives

15. Murrah Bldg Column Fails BOGOTA Demand OKLAHOMA Demand El Nogal Column Survives Fails Computed

16. Dominant Difference Murrah Bldg Column Fails BOGOTA Demand OKLAHOMA Demand El Nogal Column Survives Fails Transverse Reinf. Ratio 0.25 % 1.8 % Transverse Reinforcement Required by Colombian Code for Earthquake Resistant Design 36 by 20 in. 40 by 40 in.

17. The Pentagon

20. Before Impact (Engines dropped outside) Before impact. Note fuel distr. in wings

21. Column cuts into cockpit

22. Right wing cut near end Wing tip is cut by column

24. Wing fuel destroying columns. Column in fuselage intact. Right wing shredded. Columns fail.

25. Column in fuselage torn. Buckle near rudder. Fuel in fuselage damages columns Buckle in fuselage

26. Wings and fuselage shredded. Airplane shredded

29. WTC Impact Simulation Oscar Ardila Ingo Brachmann Christoph Hoffmann Ayhan Irfanoglu Voicu Popovic Santiago Pujol Paul Rosen

30. Problem Set-Up Boeing 767-200 (AA11) WTC Floors (89-110) Mass 767  83 t (183 kips) Mass Fuel  30 t (67 kips) Mass 767  83 t (183 kips) Mass Fuel  30 t (67 kips) Mass Impact  113 t (250 kips) Mass Slab per Floor  907 t (50 psf) v impact  200 m/sec (450 mph) v impact  200 m/sec (450 mph)

31. Boeing 767 – Overall Dimensions 48.5 m 47.6 m 15.8 m 4.7 m (interior)

32. Mass-Distribution – Boeing 767-200

33. Materials Materialf y (ksi)  u (%) Steel42-10040 WTC Materialf y (ksi)  u (%) Aluminum5512 Titanium12512 Boeing 767

37. The Comp-Intensive Perspective

38. Level Purdue Simulation 18 Story 991 Story 981 Story 9716 Story 9614 Story 9517 Story 943 Summary of Computed Damage in Core Columns

39. 12 fractured (story 95)Kajima Corp., Impact Analysis 1 severed; 2 heavily damaged (story 96)NIST, Less Severe Impact Analysis 6 severed; 3 heavily damaged (story 95)NIST, More Severe Impact Analysis 3 severed; 4 heavily damaged (story 96) 3 severed; 1 heavily damaged (story 95) NIST, Base Case Impact Analysis 23WAI, Impact Analysis 4-12MIT, Impact Analysis Number of Core Columns Damaged (maximum in a story) Investigating Team

40. Number of Core Columns "Damaged“ in One Story 0 5 10 15 20 25 123456789

41. Light Perspective

44. ECCENTRICALLY LOADED COLUMN

45. Total Eccentricity

46. Moment kip*ft Mid-Height Deflection, in. RESISTANCE

47. Moment kip*ft Mid-Height Deflection, in. Moment Demand at Mid-Height

48. Moment kip*ft Mid-Height Deflection, in. Resistance Demand Equilibrium

49. Moment kip*ft Mid-Height Deflection, in. Reduced Resistance

50. Moment kip*ft Mid-Height Deflection, in. Resistance Demand

51. One Story Two Stories

52. Speculation If all core columns had survived, but all the insulation had been lost The core would have collapsed when the column temperature exceeded ~700 degrees C

53. Speculation If insulation had not been lost The core would not have had a total collapse even if the maximum number of columns calculated to have been damaged had been lost.

54. Speculation It is true that there all sorts of combinations in between those two extreme views. So far there is no indication that any one can be proven or falsified categorically by calculation.

55. What should we conclude? Detail Toughness Insulation