Dr. S. Shyam Sunder

Lead Investigator

Deputy Director, Building and Fire Resea

National Institute of Standards and T

U.S. Department of Commer

NIST Response to the World Trade Ce

Federal Building and Fire Safety Inv

of 

the World Trade Center Disas

Consideration of Public Commen

Final Report on the Collapse of the WTC 

September 12, 2005
Nature of Changes Nature of Changes

 Multiple additions and wording changes to emph

clarify aspects

 Numerous editorial changes Added one primary finding Modified six recommendations (3 amendments,  Clarified the back-up text for several of the recom

including definition of tall buildings used in the re

 Greatly enhanced index of topic

s covered in the 
Unchanged Recommendations Unchanged Recommendations

 Group 1: Increased Structural Integrity

1. Prevention of progressive collapse and failure an

systems

2. Estimation of wind loads and their effects on tall 3. Allowable tall building sway
Unchanged and Amended Recomm

Unchanged and Amended Recomm

 Group 2: Enhanced Fire Endurance of Structure

4. Fire resistance rating requirements and construc5. Fire resistance testing of building components an

test data to quantify untested building componena national facility for studying and testing the comassemblies, and systems under realistic fire cond

6. In-service performance requirements and inspec

sprayed fire resistive materials

7. “Structural frame” approach
Unchanged or Amended Recomme

Unchanged or Amended Recomme

 Group 3: New Methods for Fire Resistance Des

8. Burnout without partial or global (total) structural 

uncontrolled building fires

9. Performance-based design and retrofit of structu10. New fire-resistive coating materials, systems, an11. Evaluation of high performance structural materia

expected in building fires
Unchanged and Amended Recomm

Unchanged and Amended Recomm

 Group 4: Improved Active Fire Protection

12. Performance and redundancy of active fire protect

accommodate the greater risks associated with ta

13. Advanced fire alarm and communications systems 

continuous, reliable, and accurate information on lmanage the evacuation process; all communicatiofor the pre-installed dedicated firefighter telephone need to be designed and installed to have the samand increase survivability above that specified in p

14. Advanced emergency fire/control panels with more 

from the active fire protection systems to provide t

15. Improved transmission to emergency responders, 

storage, of information from building monitoring sy
Unchanged and Amended Recomm

Unchanged and Amended Recomm

 Group 5: Improved Building Evacuation

16. Public education and training campaigns to impro

occupants’ preparedness for evacuation

17. Tall building design for timely full building emerge

occupants; stairwell capacity and stair discharge be adequate to accommodate counterflow due to by responders. 

18. Design of occupant-friendly evacuation paths tha

functionality in foreseeable emergencies

19. Planning for communications of accurate emerge

building occupants

20. Evaluation of alternative evacuation technologies 

occupants equal opportunity for evacuation and temergency response access
Unchanged Recommendations Unchanged Recommendations

 Group 6: Improved Emergency Response

21. Fire-protected and structurally hardened ele22. Effective emergency communic

ations syste

emergencies

23. Enhanced gathering, processing, and delive

information to emergency responders

24. Effective and uninterrupted operation of the 

control system for large-scale building emer
Unchanged Recommendations Unchanged Recommendations

 Group 7: Improved Procedures and Practices

25. Provision of code-equivalent level of safety and c

designed and as-built safety by nongovernmentagovernmental entities

26. Egress and sprinkler requirements for existing bu27. Retention and off-site storage of design, construc

and modification documents over the entire life oavailability of relevant building information to resemergencies

28. Design professional responsibility for innovative 

structural and fire safety systems
Unchanged and Amended Recomm

Unchanged and Amended Recomm

 Group 8: Continuing Education and Training

29. Professional cross training of fire protection 

architects, and structural engineers; upgradregulatory and fire service personnel

30. Training in computational fire dynamics and 

analysis
Definition of Tall Buildings Definition of Tall Buildings

 From:

 Buildings over 20 stori

es in height: NIST has found that th

on emergency responders of climbing 20 or more stori

es m

conduct effective and timely firefig

hting and rescue operat

emergencies without f

unctioning elevators. Better knowle

impacts through research could refine the definition of tall 

 To:

 NIST has found that the physiologi

cal impacts on emergen

climbing numerous (e.

g., 20 or more) stories makes it diffic

and timel

y firefighting and rescue operations i

n building em

functioning elevators. Considerati

on and better knowledge 

ladder height, physiological factors involving emergency reoccupants, use of worki

ng elevators, and i

nstall

ation and u

elevators could refine the currently used definition of tall bmultiple threshold levels.
Clarification to Findings Clarification to Findings

Inserted a clarification into the Executive Summ(Outcome of the Investigation):

NIST found no corroborating evidence for ahypotheses suggesting that the WTC towerdown by controlled demolition using explosprior to September 11, 2001. NIST also did evidence that missiles were fired at or hit thInstead, photos and videos from several anshowed that the collapse initiated at the fire floors and that the collapse progressed from floors downward, until the dust clouds obsc
Publication of Reports on the WTC 

Publication of Reports on the WTC 

 43 reports to be downloadable from the N

site by late September or early October 2

 43 reports to be available on two CDs in O Limited number of hard copies of NIST NC

available in October, 2005
Planned Schedule for WTC 7 Repo

Planned Schedule for WTC 7 Repo

 January 2006

Completion of tec

 March 2006 Draft reports for r April 2006 Draft reports to N May 2006 Reports for public  June 2006 Publication