WTC: LIGHTWEIGHT STEEL AND HIGH-RISE BUILDINGS

BY FRANCIS L. BRANNIGAN, SFPE (Fellow)

My brain probably resembles a hard drive that is heavily loaded and has not been defragged. A number of people have said they’d like to pick my brain about the World Trade Center (WTC) and high-rise buildings in general. Here are the pickings.

SOME HISTORY

The Port Authority (PA) of New York and New Jersey is a bistate agency that operates like a foreign government-it is not subject to New York City building codes. The WTC buildings were built unsprinklered, as were almost all high-rise office buildings in New York City in the early 1970s. For many years, the only sprinklered office building was 85 John Street, the headquarters of the National Board of Fire Underwriters. Scores of high-rise loft buildings in the clothing-related industries in midtown were sprinklered as a result of the 1911 Triangle Shirtwaist Fire.

The New York code emphasized “compartmentation.” The Fire Department of New York (FDNY) relied on “experience” in small-area, low-fireload prewar buildings. For a substantial period before World War II, there had been no serious fire in an occupancy in a high-rise office building. A small plane crashed into a high-rise building on Pine Street, and there was a wire chase fire in the Equitable Building. There were serious working fires in the midtown sprinklered factory lofts. These were generally fires in garment factories that started amid the fabric cuttings under wide cutting tables that deflected sprinkler water. Rubbish in freight elevator areas was also a problem. Rarely was there evacuation except in the immediate fire area. Fire Bell Club Founding Member John Sarno, who was a clerk in such a building, came down to watch a working fire with other buffs. He was docked for the time. When he retired from FDNY, he was the senior lieutenant.

In 1932 in high school, I was assigned the topic “The Empire State Building in Flames” and wrote why it would not happen.


[1] This was an extremely hot fire. The elongation of steel tore the connection apart. The floor above opened up before the office occupants evacuated.

Compartmentation worked sometimes. A fire was discovered in a loft late on Sunday evening when a tenant in the next building reported smoke. The loft was completely burned out. The cinder concrete floor was glowing red. (Much of the concrete used in New York in the early days used cinders as aggregate. In many cases, the cinders were not fully burned.) However, the Westvaco fire at 293 Park Avenue was confined to the compartmented area with the help of 500 firefighters.

There was great pressure to get high-rise buildings built and to eliminate “burdensome codes.” “After all, the experience was good”; developers who were large political contributors pushed hard. One declared, “When my building is finished, you could not burn it with a blowtorch. The problem is with the stuff the tenants bring in.” Nobody pointed out that his whole purpose in building the building was to make money accommodating the needs of tenants.

THE PORT AUTHORITY

The Port Authority (PA) placed great reliance on the fact that its guard force consisted of police officers trained to be first responders. After one or more serious fires in wire chases, target areas were sprinklered. I understand that New York State required that its floors (60, if memory serves) be sprinklered. [Building Construction for the Fire Service, Third Edition (BCFS3), p.502]


[2] The debris on the floor is ‘fireproofing’ knocked off by plasterers so they could meet their dimensions on the 30th floor of the Bank of America Building in San Francisco. (Photos by author.)

At the 1969 National Fire Protection Association Fall Meeting, in New York City, a PA staff member presented a rosy picture of its construction fire protection. FDNY Chief of Department John O’Hagen got up and said, “You have reneged on a promise to use treated plywood for formwork to save $1 million. You have created a seven-block-long lumberyard. We cannot be responsible for damage to the structural steel.”

The Hudson tubes (now PATH), a subway to New Jersey, passed through the excavation completely exposed. A single line of sprinklers along the top was supposed to protect the tubes. I thought their fire protection concepts naïve.


[3] Note the bare steel column above the ceiling line.

When Kennedy Airport was still called “Idlewild,” a large group was invited out to see the airport’s new crash truck. When they started the foam nozzles, they delivered a weak watery solution. The wrong part had been installed in the foam water mixer. I was told that they had tested the pump only with water because “foam solution was too expensive to be used except on a fire.”

FIRST INTERSTATE BANK FIRE

FDNY Midtown Deputy Chief Elmer (Bud) Chapman (Ret.), a foremost expert in high-rise fire protection, told me, “First Interstate was a demonstration project for (nonasbestos) MonocoteT. It was the best I ever saw, better than anything in New York.” The 1988 fire was in a wide-open trading area that occupied an entire floor. The security guard force kept turning off fire alarm signals.1 A maintenance man sent to investigate died.

The fire department was notified by a citizen in a building several blocks away. At an NFPA meeting, a senior fire officer was asked what he thought would happen if the fire started in the daytime. His opinion was that employees would have used fire extinguishers and fire hose to contain the fire. I was dubious. These people are making or losing thousands of dollars in trades every minute. I thought it would be like the Bradford Stadium fire in England, where the fans kept watching the soccer game as the stadium burned around them. After 9/11, I think that all would bail out in a hurry.

THE EMPIRE STATE BUILDING

This structure suffered at least two major fires in addition to the plane crash in 1945. One was a multistory fire in a wire shaft. The other was a multiple-alarm fire in an office that had had cork paneling applied to the walls.

HVAC

About 25 years ago, some fire protection engineers and HVAC (heating, ventilating, air conditioning) types teamed up to advance the concept of controlling high-rise fires with manual suppression combined with manipulation of the HVAC system to remove smoke as an alternative to expensive sprinkler protection. Chief Chapman, an NFPA 92A (Smoke Control Systems) committee member, was a severe and very unappreciated critic of this concept (BCFS3, p. 489). At a Washington seminar, I pushed to get on the program with an opposing view. I was granted time during the coffee break.


[4] A terrible job of ‘fireproofing.’ The contractor swept up overspray, placed it on the bottom flanges, and sprayed over it.

At an International Association of Fire Chiefs meeting, an enthusiastic proponent named “Semple” declared-and the IAFC published-“Let the fire burn, but let it burn clean.” His paper was published in the proceedings. This concept ignored the following:

  • The heat may prevent firefighters from holding handline positions;
  • The heat is deteriorating the “fireproofing”; and
  • All around the “clean burning” fire, combustibles are degrading and generating huge quantities of toxic and flammable gases.

A professional organization shouldn’t publish such statements in the proceedings without an adequate rebuttal.

LIGHTER BUILDINGS

Developers, builders, and architects wanted lighter (and thus cheaper) buildings. Spray-on fireproofing was invented. Each piece of steel was sprayed with an insulating coating that contained asbestos. Airborne asbestos fibers became known as a hazard early on. Protection was first provided for installers; then preventing the escape of the fibers outside the building was required. No one asked what the situation would be after a fire. Asbestos contamination was the death knell of the One Meridian Plaza building in Philadelphia, which could not be economically cleaned up after a 1991 fire. (See pp. 289-301 of BCFS3 for details on the deficiencies of various types of “fireproofing.”)


[5] When a fire occurred, the improper fireproofing failed, and the steel was distorted. Repairs cost as much or more than it cost to build the building.

I have pictures of a state-owned building in California. A friend took pictures of the totally unsatisfactory spray “fireproofing.” When a fire occurred, the structure was so badly damaged it cost more to repair it than it had cost to build. I was taken to an upper floor of the Bank of America building to see the huge table in the Director’s Room. The floor was littered with spray fireproofing knocked off columns so plasterers could meet their assigned dimensions.

THE STEEL INDUSTRY

Until about the 1950s, the steel industry had no concern about the weight of concrete required to “fireproof” (a seriously inaccurate word-“insulate” is better) steel. The more concrete, the more steel was required to carry the weight. The Inland Steel Company developed reinforcing rods that made concrete high-rise construction practical. Some steel people called Inland “a traitor to the industry.” The steel industry developed and promoted floor ceiling assemblies consisting of bar joists, corrugated, left-in-place steel forms topped with concrete with lay-in ceiling tiles below. With this assembly, they received fire resistance ratings at Underwriters Laboratories. In the first edition of BCFS (1971), I pointed out the flaw in this system. The loss of a single tile would expose the entire steel truss structure to the fire.2

UNPROTECTED COLUMNS

The industry went further. It promoted the idea that “fireproofing” was not required on columns as they passed through the ceiling void because the “column was protected by the ceiling.” I thought this dishonest because the loss of a single tile would expose the column to the full force of the fire. I was sent a report of a test the industry sponsored, conducted at National Gypsum, showing that this worked. However, Factory Mutual, which had witnessed the test, had stamped the report “one-story building or top floor only.”


[6] At Montgomery College in Rockville, Maryland, where I taught, this improper air ventilation duct completely compromised the floor and ceiling assembly in the print shop, which probably had the highest fire load in the building.

Buildings in Montgomery County, Maryland, including the leased building in which I worked for the Atomic Energy Commission, were so built. The building department told me that it was BOCA approved. I had heard that the industry was going to promote this concept widely based on the cited tests. In the second edition of BCFS (1982), I pointed out that this was a direct contradiction of the steel industry’s “Fire Protection through Modern Building Codes” (see BCFS3, p. 298). I attacked the concept vigorously. When I mentioned this practice in a group of building code hazards for publication by the International Association of Fire Chiefs, BOCA denied it had ever approved this practice.

WTC

Wide-open, clear spaces are the rule for modern offices. Such construction would be very expensive if previous methods were used. In the WTC, bar joists up to 60 feet long spanned the space between the central core and the exterior wall of vertical Vierendeel® trusses. In a November 11 New York Times article, a consultant, named Osterass, said that fireproofing was sprayed on all steel. I have never seen sprayed fireproofing material on bar joists. I have never heard of any tests on such a method. This is not to say that such tests have not been conducted.

All high-rise buildings move in the wind. This is not noticeable in heavier older buildings. Some newer buildings oscillate severely. Tuned mass dampers were installed in the John Hancock Building in Boston after it was built and, at the time of construction, in New York’s Citibank Building, to dampen the oscillations.

One news report said that the WTC spray-on fireproofing would shake off as the building oscillated in the wind and that it was replaced “at each change of tenant.” Fire protection measures must always be in place.

ELEVATOR AND STAIR ENCLOSURES


[7] This opening into the truss void or ‘truss loft’ stayed open, compromising the unprotected steel bar joists in the print shop for months. I must say that the college administration was not delighted with professional advice from the academic staff.

In earlier buildings, elevator and stair shafts featured masonry enclosures. In many cases, they were also designed to resist the shear force of the wind. In the more recently constructed buildings, gypsum board on steel studs provides the fire resistance. In the One Chase Plaza Fire in New York some years ago, hose streams knocked out the gypsum board and, in Chief O’Hagen’s words, “We had a 40-story open well in the building.” The gypsum board was a source of the huge clouds of choking dust in the WTC incident.

STANDPIPES

In earlier high-rise buildings, standpipes were intended to supply “house lines” for occupants to use to fight fires and for fire department use (except under extraordinary circumstances, such as if the truck company were to find fire and had no engine company at hand. Fire departments would then discard the house line and connect their own hose to the outlet.) Tanks located at various levels in the building provide the pressure. At outlets well below the tank, the pressure on the outlet would be too high. A simple pressure reducer provided at the outlet reduced the pressure on the hoseline. A cast iron piece held the setting. The fire department could break this piece and thus be able to open the valve fully to get adequate pressure.

At the One Meridian Plaza Fire, the building was equipped with a “sophisticated” pressure regulator that required a special tool to increase the pressure. The late Lieutenant Andrew Fredericks of FDNY pointed out that such sophisticated valves cannot be used to augment the fire flow (flowing water into the standpipe riser with a supply line through the hose valve) as was the case with the old standard valves.3

FIRST INTERSTATE FIRE

The standpipe was put out of service, apparently without the fire department’s knowledge, so automatic sprinklers could be installed. The building engineer was taken off the roof by helicopter and returned to the building by police car.

There was a huge fire load in the WTC-computers, papers, furniture-which continued to burn for weeks in the wreckage. In the First Interstate Fire, a similar load sent flames that were roaring out the windows and autoextending to the floor above when firefighters arrived in response to a phone alarm from blocks away.

THE ONE MERIDIAN PLAZA FIRE

A similar fire in Philadelphia’s 40-story One Meridian Plaza Building did severe structural damage. The structural damage and asbestos contamination were from a fire that had started in a pail of rags. Curiously, this historic fact passed into history without notice. The owners had fought off sprinklers, and the guards did not allow fire alarms to be transmitted to the fire department.

No one, to the best of my knowledge, has ever calculated the losses of all the tenants whose businesses were destroyed.

FIRE SUPPRESSION

The First Interstate Fire was stopped at a vacant floor. The One Meridian Plaza Fire was stopped when it hit a floor that had been sprinklered at the tenant’s insistence; the sprinklers were augmented by fire department pumping. Some high-rise fires that are low enough in the building have been brought under control by exterior attack, after interior personnel had withdrawn to safe locations. In the days of lighter fireloads, the entire second floor of a high-rise was a fully involved drafting room. A deck pipe operated from a wagon was used to sweep the floor and knock the fire down so interior units could enter the floor. A number of high-rise fires, including those mentioned here, are summarized and referenced in BCFS3, pp. 506-516.

Fire departments should campaign for retrofitting sprinklers in all high-rise buildings. A daytime fire in a high-rise building could well be a costly disaster. Sometimes money talks better than blood and tears.

ANATOMY OF A COLLAPSE

The Learning Channel (TLC) presentation of “Anatomy of a Collapse” describes how the loss of the floor trusses in the WTC destabilized the columns. For a more detailed explanation of the effect of losing the bracing on columns, see BCFS3, pp. 61, 64, and 65. Note the error in the caption of 2-30-“arithmetically” should read “geometrically,” as in the text above.

When the floor trusses brace the columns, they act like columns when subjected to lateral stresses. Dr. W. Zuk, in Concepts of Structure, says that while beam failures are gradual, column failures are sudden and catastrophic.4 The TLC presentation states that in the WTC, there were only a few small office fires over the years. There was at least one, and possibly more, serious multistory wiring chase fires, which led to partial sprinkler protection.

WARNING

We cannot accept the conclusion that this collapse was a unique occurrence that would never be duplicated except for another such attack. The heavy fire loads of modern offices and vulnerable bar joist construction in unsprinklered buildings, together with the substantial time delays inherent in manual fire suppression, combine to create a serious hazard in the case of a “normal” fire. This is even more significant in cities that do not have the enormous resources required for suppressing an advanced fire.

SUGGESTIONS FOR FIRE DEPARTMENTS

I offer the following suggestions.

  • Study the entire Chapter 11 of BCFS3, “High Rise Construction,” and Chapter 7, “Steel Construction.”
  • Seek the cooperation of high-rise owners, operators, and tenants. Some may be more cooperative if they had no responsibility for planning and building the structure.
  • Compile information on high-rise buildings in your jurisdiction, particularly those that have long-span bar joists.
  • Study page 501 of BCFS3 for arguments that might help your sprinkler recommendations.

Endnotes

  1. Nelson, Harold, SFPE (Fellow), “Science in Action,” NFPA Fire Journal, July 1989. The timing of the successively firing detectors was very useful in plotting the growth of the fire.
  2. When the first edition of BCFS3 was printed in 1972, a steel industry spokesman, when asked his opinion, said, “It is a good book for people who can’t read.” At a meeting I demanded that he cite the “errors” in the book. He said, “It is a good book. Can you use me teaching at Montgomery College?”
  3. Andy was a fountain of information on water use. Go to the Fire Engineering Web site at www.fireengineering.com and enter his name to find a treasure trove of information on this subject.
  4. Zuk, W. Dr. Concepts of Structures. (Litton Educational Publishing, 1963).

FRANCIS L. BRANNIGAN, SFPE (Fellow), recipient of Fire Engineering’s first Lifetime Achievement Award, has devoted more than half of his 59-year career to the safety of firefighters in building fires. He is well known for his lectures and videotapes and as the author of Building Construction for the Fire Service, Third Edition (National Fire Protection Association, 1992). Brannigan is an editorial advisory board member of Fire Engineering.

No posts to display