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.

The Root of The Problem Offset Resistance SOLUTIONS

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

Murrah Federal Building Oklahoma City 19 April 1995

G20 Transverse Reinforcement Spacing 16 in.

El Nogal Building Bogota, Colombia 7 February 2003

( kip KE kip Displacement, in. PE  ) in    Bogota, El Nogal

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

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

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.

The Pentagon

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

Column cuts into cockpit

Right wing cut near end Wing tip is cut by column

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

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

Wings and fuselage shredded. Airplane shredded

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

Problem Set-Up Boeing (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)

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

Mass-Distribution – Boeing

Materials Materialf y (ksi)  u (%) Steel WTC Materialf y (ksi)  u (%) Aluminum5512 Titanium12512 Boeing 767

The Comp-Intensive Perspective

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

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

Number of Core Columns "Damaged“ in One Story

Light Perspective

ECCENTRICALLY LOADED COLUMN

Total Eccentricity

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

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

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

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

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

One Story Two Stories

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

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.

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.

What should we conclude? Detail Toughness Insulation