Bringing the Heat to Bowen Lab

With his breakthrough research on large floors and full-length columns, a structural engineer is gaining a greater understanding of a building’s overall fire-structure stability.

The square footage alone—some 66,000 feet—allows for big-time testing in Purdue’s Robert L. and Terry L. Bowen Laboratory for Large-Scale Civil Engineering Research. From the 32-foot building model tested for its resistance to earthquakes to the numerous projects that call for a large-scale look, Bowen Lab facilitates big breakthroughs. But for Amit Varma, an associate professor of civil engineering, his Bowen research space is yielding results that are downright hot. And should we use the parlance of sports writers, you might even say that this researcher is on fire.

Ushered into the 21st century as we were with the images of the twin towers of the World Trade Center collapsing upon themselves, the interest in fire-structure stability has likewise exploded. Builders want to know: Is my structure safe? Will it be adequate in a design-level fire? And Varma’s sponsors—the National Science Foundation, the National Institute of Standards and Technology, and the American Institute of Steel Construction among them—are more than just funding sources. They’re eager to find those answers.

For Varma, the answers are being found in a cutting-edge, fundamental approach that takes into account the whole building’s stability, not just columns or small sections. “We’re evaluating the performance of building structures under a realistic fire loading,” he says. “This is a multidisciplinary field of structure fire interaction. It involves mechanical engineers who work in the field of combustion, computational fluid dynamics, and heat transfer analysis, along with structural engineers who are experts in experimental behavior of structures and collapse and the stability analysis of structures.”

As compared to how buildings stand up in other extreme events, such as earthquakes or dangerous winds, the understanding of structural fire design in the U.S. has been somewhat limited, according to Varma. “It’s not that it hasn’t been good,” he explains. “It’s just that the technology is not based on a fundamental understanding of structural behavior and collapse.”

To get at that better understanding, Varma designed a large-scale experiment specifically for use in Bowen Lab. Using a radiation-based heating system, which Varma compares to an electric stovetop that many of us use in our kitchens, his team can literally bring the heat to an entire floor system measuring 100 square feet. An open flame would be much harder to control, not to mention particularly dangerous in a structure’s lab. The radiation-based heating, however, actually allows the researchers to apply heat, and more of it, in a very confined setting. And as a structural engineer intent on gaining a physical understanding of how things fail, this close proximity and hands-on research is a great aid that pinpoints where both the failure initiates and how it propagates.

Over the next four to five years, Varma, with up to five PhD students, will perform various experiments on columns, subsystems, and composite beams, as well as floors. It’s all work that will have been bolstered by state-of-the-art computer simulations they’ve done over the past year. “We use the results of the simulation to define our experiments,” he says. “The purpose of the simulation is to find out how the building behaves and what its weakest link is.”

If Varma can make the weakest link stronger, the overall structure can be improved. “A building is not a single column,” he says. “Our experimentation is focusing on a more fundamental understanding of a building’s overall performance.”

And as Varma and his group build on this better understanding and predictability, the stronger, safer buildings are sure to rise and even stand tall in case of disasters.

- William Meiners