Fire Tests Give Insights Into WTC Tragedy

Feb 1, 2004 12:00 PM

The National Institute of Standards and Technology (NIST) is conducting a 24-month building and fire safety investigation to study the factors contributing to the probable cause (or causes) of post-impact collapse of the World Trade Center Towers (WTC 1 and 2) and WTC 7.

One of the main goals of the investigation, which is being conducted under the authority of the National Construction Safety Team Act, is to serve as the basis for improvements in the way buildings are designed, constructed, maintained, and used. In the fire safety arena, the goal is to identify, as specifically as possible, areas in current national building and fire model codes, standards, and practices that warrant revision.

One part of these tests was recently completed. It involved fire testing of a typical WTC workstation in Tower One.

The extent, intensity, and duration of the fires in each of the three WTC buildings played a pivotal role in their eventual collapse. Because of the dearth of information from inside the WTC buildings on the progression of the fires, the fires must be reconstructed using available information on the buildings' interiors and the photographs of the exteriors.

The goal of the workstation tests is to provide input to NIST-developed fire modeling software so that investigators can accurately simulate the complex burning of the combustibles and determine how the fires contributed to the collapse of the WTC buildings.

In the tests, NIST has included the effects of rubble and aviation fuel on the burning rate of the workstations, with the goal of obtaining the combustibility properties of the workstation's actual components.

The workstation mockup was the same as one used by Marsh & McLennan Companies, a tenant of WTC 1. The firm occupied the floors where the hijacked aircraft hit the tower. The mockup was an 8 ft. by 8 ft., four-sided cubicle that incorporated a laminated particle-board desk surface on three sides, a bookcase holding 70 lb. of paper products, a largely plastic chair, a computer system, and nylon-faced carpet tiles. An additional 65 lb. of paper products were distributed throughout the office setting.

The peak heat release rate from the workstation in this test occured at 8.5 minutes after the start of the test. The fire consumed 386 lb. of combustible materials in 33 minutes.

Eventually, NIST will use the results to generate a database on the thermo-physical properties of the materials for input to a fire dynamics simulation tool — allowing researchers to study the effects of the fire on the building.

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