NEW YORK, NY January 10, 2003 — In the next few months, federal investigators will begin sending out hundreds of surveys to survivors and rescue workers who were at the World Trade Center on September 11th. The surveys are part of a larger, 2 year study into precisely how the twin towers collapsed. Researchers are hoping to help the building industry develop better evacuation procedures and safety features. Most of their work is taking place in a federal lab in Gaithersburg, Maryland just outside of Washington. WNYC's Beth Fertig visited recently to see what the scientists are learning so far.

It's a bit of a shock when you first see the twisted red beams. They almost look like they're rusted. But it's just the bare bones of steel. The aluminum coating was blown away on September 11th. The wreckage of two towers that once dominated the city skyline seems out of place on the green lawn of this tidy research campus surrounded by institutional, 1960s architecture. In this antiseptic environment, the emotional force of the tragedy is buffered. The beams are now in the hands of scientists.

GAYLE: (Clank) We keep track of everything. Hundreds of pieces.

Frank Gayle is a metallurgist at the National Institute of Standards and Technology, or NIST. Maybe it's just a memory. But if you step close enough you can just detect the familiar, sour smell that dampened Lower Manhattan. There are nearly 200 pieces of steel. And they're all being meticulously tracked.

GAYLE: as you see here there's an identification number which keeps track of exact location and where it came from.

Gayle and his team have spent the past few months figuring out where each surviving beam was located in the World Trade Center.

GAYLE: Well let's walk over here

Inside the engineering mechanics lab Gayle points to 2 gnarled columns, once three stories high. Their tops have been completely shredded. By mapping out the disaster, researchers believe these were the columns in the North Tower that were struck by the first plane. Gayle says his team figured this out by examining photographs of the destruction, and then finding the original markings from when the beams were first constructed in the 1960s.

GAYLE: The perimeter columns all have identification numbers on them if they survived the fires and the collapse. And you can see the numbers that are stenciled on this piece here and that's how we know that it was column A30. A means it's from the World Trade Center 1, north tower, 130 is in the center of the north face, and stenciled on there is 93 to 96 so we know exactly what floors and where this piece came from in the building.

These tangled pieces of steel hold the key to understanding exactly how the World Trade Center collapsed. Now, that might not seem like such difficult question. Everyone agrees the towers were weakened when they were struck by airplanes. A preliminary study by the Federal Emergency Management Agency also found the resulting fires then caused the steel to lose its strength. But what role the fires and the impact each played is still being debated. There are competing theories, explains Dr. Shyam Sunder, who's now the lead investigator at NIST.

SUNDER: Whether the fires weakened the floors and brought the buildings down or the fires weakened further the columns and brought them down still remains, still has not been finally decided which if the two mechanisms really were at play.

In other words, did the towers collapse from the outside in? Or from the inside out? Last year, Congress gave NIST 23 million dollars to provide those answers in order to improve on building safety. The agency is now putting its state of the art technology to work.

ENGINEER: Three, two, one SPLAT!

Engineers are using a machine called a Kolsky Bar. It's a tool used to measure how metal responds to pressure. But it's really more like an air-powered battering ram. A tiny sample of World Trade Center steel, about the size of a lithium battery, is placed between two rods. Then, an airgun fires a projectile into one of the rods. And the impact is measured.

RHORER: That's one you've already used right? Measure the new one, and then put a new one in.

ENGINEER: Three, two, one, fire SPLAT!

The collision is so strong it can replicate the force of an airplane hitting a building at 500 miles an hour. Mechanical Engineer Dick Rhorer then measures the samples to see how much they shrink, or strain under pressure.

ROHRER: We're probably about in the same range as if you bent a beam that was originally standing up straight and now it's bent clear over where it's horizontal. That's about the amount of strain we're producing here.

By sampling different pieces, researchers can enter the results in a computer and eventually simulate exactly how the building would have reacted to stress and heat.

REHM: Let's see

Doctor Ronald Rehm is studying the heat that was produced on September 11th. The walls of his tiny office are covered with photos of the Twin Towers burning. When he looks at these pictures, he concentrates on the clouds of smoke billowing over Lower Manhattan.

REHM: We took the meteorological conditions. We took the pictures. We said from the meteorological conditions and the pictures we can estimate what the total heat release, how strong were those fires. And we estimate them to be in the gigawatt range. Anywhere from a fraction to a few gigawatts. And that's the amount of energy released by a relatively large power plant.

Rehm is also tracing how the fires progressed from floor to floor. Above his desk, there's a particularly large photo of the shattered hole where an airplane entered one of the towers. If you look closely, you can see people standing by the windows. Rehm admits it's sometimes hard to focus on the science when confronted with these images.

REHM: You put aside what would bother you normally under other conditions and you say I have a job to do. I want to find out what's going on, how things progressed. You sort of divorce yourself from it. But periodically nonetheless when you get a video or some pictures which shows the people aspect of things you can still be bothered by that.

The National Institute of Standards and Technology has now become the repository for a seemingly endless collection of photos and videos of September 11th. Dr. Shyam Sunder shows an entire storage room filled with boxes.

SUNDER: Along this wall you have all the documents we've received from Silverstein this line of 10 or 12 boxes are from the insurance companies.

Sunder says his team is looking at every document connected to the building of the Twin Towers, the fireproofing and the steel that was used. His institute was given this power by Congress last year after complaints that FEMA didn't have enough authority. Some steel was recycled after September 11th and FEMA had trouble even getting the Trade Center blueprints. With time and resources now for a more thorough study, Sunder says his agency can make recommendations that could lead to changes in building design. Similar to how engineers plan for earthquakes.

SUNDER: You might see better enclosure walls to the stairwells and the elevator system. You might see better elevators able to work within the emergencies, especially to carry firefighters up the building. You might see a structural design that is better able to resist the fire, better able prevent spread of fire. And last a little bit longer with respect to fire and maybe does not have a progressive collapse of entire structure. Those are the kinds of benefits the research will lead to.

Sunder's team is still reaching out for more evidence. They're asking the public to provide more photos - especially of 7 World Trade, which also collapsed. And they'll soon be sending out surveys to survivors and rescue workers about the evacuation procedures. The final report is due by the summer of 2004. In Gaithersburg, Maryland for WNYC I'm Beth Fertig.