Meeting of the National Construction Safety Team Advisory Committee 

December 14, 2006 

Minutes 

Committee Members 

Paul Fitzgerald, Chair 

John Barsom 

Robert Hanson 

Forman Williams 

David Collins (did not attend) 

Kathleen Tierney (did not attend) 

Charles Thornton (did not attend) 

Welcome and Introduction

Mr. Fitzgerald called the meeting to order at 9:00 am. Four members of the NCST 

Advisory Committee (Fitzgerald, Barsom, Hanson and Williams) were present on the 

call, which constituted a quorum. He reminded the Committee that it was an open 

session and that the meeting was being audio web cast to the general public. He also 

noted that two individuals had requested the opportunity to speak to the Committee and 

that those individuals would call in at 10:30 a.m. to address the Committee. Mr. 

Fitzgerald pointed out that the public comment period speakers would be limited to 5 

minutes each as had been the case in previous meetings of the committee. He told the 

speakers registered for the public comment period that their comments should be limited 

to the issue of what they believe the NCST Advisory Committee should be reporting to 

Congress in its 2006 report and to the status of the World Trade Center 7 investigation. 

James Hill, Acting Deputy Director, NIST 

Dr. Hill thanked the members of the Advisory Committee for being present for the 

meeting and welcomed them on behalf of Dr. William Jeffrey, NIST Director. Dr. 

Jeffrey was unable to be present due to travel commitments. Dr. Hill offered to answer 

any questions that the Advisory Committee might have for him or for the NIST Director 

and noted that Dr. Sunder would be updating the Advisory Committee on the status of the 

Investigation of the collapse of World Trade Center 7 (WTC 7). 

Dr. Hill noted that NIST is currently in the FY07 and 08 budgeting process. The current 

outlook is that NIST will be operating under a continuing resolution for an extended 

period of time, possibly through the end of the fiscal year. The current budget situation 

will not affect the ongoing investigation of WTC 7 or the Advisory Committee operation. 
Shyam Sunder, Acting Director, Building and Fire Research Laboratory and WTC 

Lead Investigator 

Since the release of the Final WTC Towers Reports in October 2005, NIST has worked 

vigorously with the standards and codes organizations, including the International Code 

Council (ICC) process and the National Fire Protection Association (NFPA) process, as 

well as the group of building code experts that is working under a NIST contract to the 

National Institute of Building Sciences (NIBS) to formulate code change proposals. A 

large number of code change proposals were submitted by the March 24, 2006 deadline 

for the International Building Code and the initial hearings were held in September 2006. 

This was the initial round of hearings where all stakeholders, including the private sector 

are able to weigh in on code change proposals. The outcome of the code hearings was 

better than expected. The initial expectation was that most of the code change proposals 

would not be approved; however three of the proposals that deal with fireproofing 

requirements were approved. These proposals addressed bond strength, quality control, 

and application of spray-applied fire resistive materials. Also, a proposal for installation 

of firefighter elevators was approved by the assembly. 

In addition, the industry came forward strongly to say that they are going to develop an 

alternative proposal for progressive collapse. There is a very robust industry group, led 

by the National Council of Structural Engineering Associations (NCSEA). This group is 

developing a consensus-based alternative proposal and they have promised to put forward 

an alternative proposal by August 2007, the deadline for submitting proposals for the next 

code cycle. 

There are several other changes that are not only working through the ICC and NFPA 

processes but also through the standards processes of organizations such as the American 

Society of Mechanical Engineers (ASME), the American Society of Civil Engineers 

(ASCE), the American Society for Testing of Materials (ASTM), and a range of other 

organizations. NIST is committed to working with those organizations, and will continue 

to do that over the next few years. 

NIST staff have also been working on analyzing the collapse of WTC 7. NIST has taken 

a number steps and made good progress. NIST re-evaluated their initial approach used 

for this analysis and developed an updated approach that is much more robust. As a 

result of this re-evaluation, NIST re-competed the contracts and has a good group of 

contractors working with the NIST team to conduct this work. 

 

Therese McAllister, Project 6 Co-Leader 

Dr. McAllister briefed the committee on the progress that has been made on analyzing 

why and how the 47-story WTC 7 building collapsed at 5:20 pm on September 11, 2001. 

(Presentation: "WTC 7 Technical Approach and Status Summary", December 12, 2006, 

Therese McAllister, NIST) 

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Dr. Sunder noted that the end product of the WTC 7 investigation will be three reports. 

One will be a companion to the original summary report for the towers (NCSTAR 1). It 

will be written in a narrative format so that it is accessible to a large audience. The 

second will be a detailed technical report, written by NIST staff, along the lines of the 

previous technical reports, with all of the details and assumptions used in the analysis. 

The report will cover all aspects of the investigation of WTC 7. Appendices will include 

the seismic analysis and the review of the Consolidated Edison Substation, preliminary 

structural response analysis, and the hypothetical blast scenarios. The third report will be 

written by ARA on the modeling work they and their subcontractors have performed in 

support of the investigation. 

Q: What is going to be the final result of the analyses and how well are we going to be 

able to defend it? 

A: The state of our analysis at this point is at the same state as where we were with the 

towers in early 2004, at which point we were not even in a position to speculate as to 

whether or not we would have a probable collapse sequence. We are going to bring the 

best science we can to the problem and try to consider “what-if” scenarios. Obviously, 

there might be the leading hypothesis, but we will also try to ask the “devils advocate” 

question as to whether this is a unique solution or one of many that could have given us 

the same answer. At this point it is fair to say that we are not in a position to give an 

assessment of where we might end up in a few months from now. 

C: Maybe the first step is to make a list of what we really know as fact and then what are 

the assumptions that are being made above and beyond those facts. 

A: We have tried to analyze the interviews to generate a timeline of events and we are 

going to do the same thing with the photographs and with any other hard evidence that 

we have. It is an excellent suggestion for us to move forward. 

Q: Will you, like you did for the Towers, put some range of likelihood on the 

assumptions so that you can do a variance in terms of the analysis? 

A: In the case of the Towers, we used a statistical process to understand uncertainty in 

variables and when we get to a point where we believe that we are close enough we will 

try and do that. We will certainly try to quantify uncertainty if we are able to do it in a 

rigorous fashion. 

Q: In your blast analysis, at what time of day did these blasts occur? 

A: Part of what we are evaluating is what could take place, within the realm of designing 

a method to remove these columns, considering the time available and when it would 

have to occur. 

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A: We are doing the blast analysis primarily for completeness. As we have said, we 

have not seen any evidence of controlled demolition or a blast event. As you know we 

put out a fact sheet just a few months ago with regard to the towers where we state that 

any blast material would have to be pre-positioned and triggered to synchronize with the 

collapse of the building. We want to try and see if a hypothetical event, even if such 

improbable events were synchronized to take place, could be discriminated from the 

other more normal events that we think are the primary reasons why the building 

collapsed. 

Q: On slide 13, both of the Damage States have damage above Floor 7 and also on 

Floors 5 and 6. Am I reading the slide correctly? Did I misinterpret what you said? 

A: The table on slide 13, shows possible different scenarios. For example, for Damage 

State 1, one possible scenario would be that the initiating event was caused by fires only 

on Floors 7-13. Another possible scenario would be that fires on Floors 5 and 6, as well 

as 7-13, caused the initiating event. There are six possible scenarios for each Damage 

State because the fireproofing condition is imposed on each of the damage scenarios. 

Since the condition of the fireproofing was not directly observed, we are considering a 

range of fireproofing conditions to understand the role the fireproofing condition plays. 

So, there are a total of 12 scenarios when Damage States 1 and 2 are considered. 

Q: Was it necessary to re-initialize the FDS analysis to account for fires observed from 

outside on different floors? 

A: Once the fire is started in FDS, it keeps going. If we reached a point where the fire 

was behaving differently than the visual evidence, then we would have to take a look at 

restarting or stopping the fire in that location to be consistent. Obviously, the evidence is 

what counts; the simulation has to follow it. 

We are also doing sensitivity analyses to find, within the reasonable range of the 

variables, if there could be things accounting for the visibility or non-visibility of the fire. 

For instance, on some of the floors there are large numbers of interior partitions between 

the core of the building and the exterior face. We need to know how long a fire could be 

hidden on the inside of a series of those partitions before you would see it break through 

and show up on the outside. As we did with the Towers, we varied the fuel load to make 

sure that the progress rate of the fires was consistent. We are pinning all of the 

simulations to those pieces of evidence that we have, such as when were the windows 

broken, where were they broken and so on. 

Q: In the best case run, how many times did you have to stop and restart the FDS 

analysis? 

A: Not more than once per run. 

Q: In one of your slides, you used the phrase “large-span floor bay.” I assume this refers 

to the portion of the building that was over the ConEd substation. Have you been able to 

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determine how the rest of the building might have been tied into this portion of the 

building over the substation and what the connecting strength for lack of a better term, 

might have been with some of those ties? 

A: The large-span floor bay referred to areas where there were fifty-foot spans between 

the edge of the core and the exterior of the building, primarily along the north face and 

the east face. The core was not centered in the building so that the south and west faces 

had shorter spans. 

Q: In 2004 you were still investigating how the critical columns that supported this large 

span area were tied back to the rest of the building and you were trying to get more 

structural drawings. If my notes from our 2004 meeting are accurate, you were looking 

to see what the ties were, the strength of those ties, and how they might have initiated a 

pull. 

A: In the structural model at that time we wanted to get better information on how the 

connections were designed in this building. NIST has reviewed the structural drawings; 

however these drawings do not include the connection details. We do have access to 

most of the other information on the structural members. To develop the information on 

the details of the connections, we have talked to the company that originally was the 

structural engineering firm for the building. We have also talked to structural engineers 

of the era who know the practice in New York City and were in a position to tell us the 

kind of detailing that would have been used in a building in the mid-1980s. With regard 

to the initiating event and the tie-back of the column to the rest of the structure, we have a 

good model of that now. Exercising the model and working on the what-ifs are being 

done at the present time. 

Q: You indicated in June that you had reviewed the seismic information, and you 

mentioned specifically what the impact might have been on the fireproofing in the 

building itself. Have you done any analysis as to what the damage might have been to 

piping, specifically the fittings of the piping that were used in providing fuel to these 

emergency generators that apparently were located through the building and in addition 

the piping that came in from the tanks that were located outside? 

A: The main focus of the review of the seismic data was to establish the timing of the 

various events and to see if there were any events that we could not explain other than the 

collapse of the Towers and World Trade Center 7. The signal strengths due to the 

collapse of the Towers were not of a magnitude that was seismically significant from an 

earthquake design standpoint or from the design or failure of a structural component or a 

piping system that might be used in a structure. There was nothing in the data that 

suggested a significant seismic event that could have ruptured the pipeline. 

Q: Is a pipeline rupture one of the scenarios that you are going to be looking at? 

A: For each damage state there is one case where we have fire on Floors 5-6 plus floors 

7-13. The 5th floor fire, as far as we know, was not a normal building contents fire and 

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our hypothesis is that it was a fire caused by the pressurized fuel line there. We also see a 

tremendous amount of fire on Floors 7-13, which are normal building fires. As we saw in 

the Towers and as we have seen in the large-scale tests such as the Cardington tests, floor 

sagging is a significant event and there is impact or distress at the connections and 

crimping at the tops of columns. These are all possibilities that we are exploring due to 

the fires that were present between floors 7-13. 

Q: Are you able to ascertain to what standard, if any, the combustible liquid piping was 

built? 

A: We did have a contractor review the fuel systems in WTC 7 and a report on this 

review (NCSTAR 1-1J) was released along with the initial Towers report. The review 

included a look at standard practices. The indication was that the piping was installed 

according to standard practice. The pressurized line was unusual, but there was no code 

requirement against such a design. If the pressurized line were to break a certain way at 

a certain time, the normal safety features in fuel systems may not have operated 

appropriately and therefore there was the possibility of building up a substantial pool of 

liquid or a spray that would have led to an intense fire. 

The scope of the ConEd study was to understand the layout and the types of equipment 

located in the building, what observations were made by the people who were in the 

substation, and if there was any information generated from that building that might be 

useful to the investigation. We were not looking at the structural details of the ConEd 

building, but we are dealing with the tie-back and the transfer trusses in other sections of 

our reports. In the ConEd study, which will be an appendix to the main report, we tried 

to identify any sequence of events that contributed to the outcome, but there was nothing 

that suggested new leads that we might want to follow. So it is therefore background and 

is there to eliminate some other possibilities that may have occurred. 

Q: In the 80 boxes of material about the Solomon Smith Barney renovation, which came 

from SOM was there information that indicated that the occupancy was atypical to the 

occupancy in the towers, such as for a typical work station arrangement that you see in 

the financial centers almost everywhere? 

A: No there was nothing unusual. The Solomon Smith Barney occupancy was on the 

upper floors. Because of the way the building collapsed, our focus is on the lower floors 

where the impact of the fires on the structure would be most likely to contribute to the 

collapse. We do have, as a result of communications with the occupants of the floors up 

through floor 13, a moderate amount of information about the types of furnishings, 

density, etc. 

Q: I do not see the need to conduct the blast analysis, based on the lack of evidence, and 

also based on the information that you have been able to gather regarding what may or 

may not have been stored in certain offices in the building. On December 6 you 

developed the hypothetical blast scenarios for the analysis of overpressures. Are you 

comfortable at this point in time telling us what those scenarios might be? 

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A We are not far enough along in the analysis to discuss the scenarios. 

Discussion of the NCST Advisory Committee Report to Congress 

Mr. Fitzgerald prepared a draft letter report to Congress which was circulated to the 

Committee members prior to the meeting in order to frame the discussion. Mr. Fitzgerald 

recommended the letter report format, rather than the more detailed reports submitted 

previously, since there had been no new investigations and little activity on the part of the 

Committee. The Committee members expressed agreement on the format and content of 

the draft report. Following discussion of a number of editorial changes, the Committee 

voted to accept the report to Congress with the editorial changes discussed. Mr. 

Fitzgerald took the action to make the editorial changes and to provide the Committee 

members with a final version for their review before submitting the report for transmittal 

to Congress. 

 

Public Comment Period

Mr. Arthur Scheuerman 

(Written comments submitted by Mr. Scheuerman) 

Mr. Jerry Leaphart 

(Written comments submitted by Mr. Leaphart) 

The meeting was adjourned at 10:45 am. 

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