Shake Table Helps Wierschem Study Effect of Earthquakes
All seems normal as a family sits down together for a meal sometime in the not-too-distant future, something done countless millions of times a day across the planet.
Without warning, the ground begins to violently shake; a major earthquake has begun.
Such events have been one of the most destructive forces throughout history, with records of them dating back nearly 3,000 years and a legacy that no doubt stretches to the earliest days of the planet.
Even in our more modern times, earthquakes have caused massive devastation, widespread loss of life, and have upended whole countries, as in the 2010 one that leveled Haiti.
Thankfully, the family in our scenario is better protected, their structure better prepared in ways past generations couldn’t have imagined, due to the hard work being done by researchers like Associate Professor Nicholas Wierschem.
Engineering, as a discipline, is often concerned with coming up with novel ideas to tackle large-scale problems that can only be investigated with small-scale solutions due to a variety of constraints.
So, while it would be prohibitively expensive to build a device to hold a house and then proceed to destroy it, tools like Wierschem’s shake table come in handy.
“After attaching representative objects to the top of the shake table, we can then use the shake table to simulate an earthquake,” said Wierschem. “Data from this testing helps inform everything from building design to materials used, and it allows us to figure out ways to reduce the impact that the earthquake will have on a structure. We can do more things than we otherwise could because of this equipment.”
When people think of earthquakes, most people likely think of disaster movies or bad television shows, where the quake starts and structures just sort of crumble.
In reality, it is much more complex. It isn’t so much that the building shakes, but rather how it shakes that plays a factor in damage to the structure.
The resonance and frequency of the waves as they travel through the bedrock and the depth at which it does so helps determine the destructive power of the quake, as does its duration. Buildings, also, have their own resonance, which plays a key role as well.
“The natural frequency at which a building most responds to waves of an earthquake is that building’s resonance frequency,” said Wierschem. “What causes the most swaying and, consequently, the most damage is when the frequency of both the quake and the building are close.”
Thanks to equipment like Wierschem’s, those forces can be better understood and better controlled. In fact, Wierschem is co-PI on a National Science Foundation project being led by CEE Assistant Professor Mark Denavit focused on seismic-damage-resistant structures that uses the table.
The table also has uses beyond earthquake simulation, with Wierschem also having used it for NASA and Office of Naval Research projects.