How do engineers know that the pillars supporting a bridge can withstand the force of thousands of cars driving over them for decades? How do we know what would happen to that bridge during an earthquake? What about an earthquake in winter?
Buildings, roads and bridges are all designed with a buffer of safety—basically, engineers round up on the numbers, a lot, and design these things to be far more sturdy than they actually have to be. But to make those decisions, they first have to know the physical limits of the materials they're working with. The best way to do that: Take a scaled version of a girder, pillar, or concrete slab and push it past the breaking point. Yes, this is, in fact, as awesome as it sounds.
The Constructed Facilities Laboratory at North Carolina State University is one of the places in the United States where this kind of research happens. In this lab, engineering researchers shake, bend, freeze, and crush the stuff that supports our world. I got to take a tour of this lab back in January, led by lab manager, Greg Lucier.
The videos here will take you through the 4500-square-foot lab and introduce you to the equipment these engineers use—from giant compression machines to something called a "Thermotron environmental chamber."
We'll start with a quick spin around the lab, just to get acquainted with the space. Then, you'll learn how some of the systems you see here work and why they're so important. Finally, you'll get to watch the lab in action.
The Constructed Facilities Laboratory is more than just a big room where engineers break stuff. The lab itself is designed to make it easy to set up experiments and apply both vertical and horizontal pressures to materials. In this video, Greg Lucier explains why the walls and the floors matter, and shows off the results of a bridge column strength test.
A building that can survive an earthquake is a building that will save lives. Shake tables are moving platforms that allow engineers to mimic the effects of an earthquake, or even recreate the shaking of a historic earthquake. In this video, Lucier shows off the lab's shake table, which is set up to test a scale model of a steel building frame.
The weather conditions a structure has to deal with in Minnesota are not the same as the conditions in coastal Alabama. That's where the Thermotron environmental chamber comes in. This metal box, which looks a lot like a walk-in freezer at a restaurant, allows engineers to cool and heat materials as they physically stress them. The Thermotron is also where the researchers make messes—spraying materials with salt water, for instance.
The Constructed Facilities Laboratory has a geotechnical side, as well. This is where researchers mock up the soil a building sits on, helping them understand what happens to different types of construction on different types of geology. It involves a deep, round pit.
Sure, you can take a piece of pipe and rig it up to some pistons and bend it around until it breaks—but how do you collect the data? In this video, Greg Lucier shows us one of the ways that engineers monitor the materials they're destroying.
What works in the laboratory is not always the same thing as what works in the real world. So how do engineers know that the results of tests like these actually apply for a real-life bridge, or a building that actually has people in it? In this video, we learn a little about the verification system that connects data to the bigger context.
Of course, I know that you all really came to this feature to see stuff actually get destroyed in the name of science. Now that we've got all the educational bits out of the way, you will get your reward. Here is one-and-a-half minutes of exploding girders, walls, columns and pylons—naturally, it's all set to the tune of the 1812 Overture, aka, "that song we play while we blow things up."
Images: North Carolina State University and the North Carolina State Alumni Association.