Earthquakes are among the most destructive natural disasters on the planet. They typically happen when the tectonic plates that form the Earth's outer shell, which are in constant motion, get stuck against each other. Pressure builds where these massive slabs of rock meet until it becomes too intense and the plates slip, releasing a massive amount of energy that creates seismic waves.
Every year, tens of thousands of people die in earthquakes around the world and the estimated cost of responding and rebuilding accounts for roughly one-quarter of annual global natural disaster losses, which ranges from $200 to $300 billion USD. And while public concern about the next Big One in North America is often focused on the west coast, the more populated eastern side of the continent faces similar seismic threats.
All of this is the backdrop to work underway in Carleton University's unique Canada Foundation for Innovation-funded structures lab, where a team of Civil and Environmental Engineering researchers is conducting tests to better understand how buildings and their internal components respond to intense shaking and, ultimately, how they can be designed differently to minimize injuries and damage.
"Mostly what we do here is try to break things," says Prof. Jeffrey Erochko, who is using new state-of-the-art earthquake simulation technology in a project with Prof. David Lau and PhD student Cameron Flude to investigate what happens to suspended ceilings during earthquakes.
"We can simulate how the movement that occurs during an earthquake affects any part of a 100-floor building, and then we push the structure to the limit to determine the exact point of failure. This will help us design better buildings that can withstand quakes."
Bend But Don't Break
Designing buildings that "bend but don't break" during an earthquake is one of the most complex challenges faced by engineers, according to Lau, but a lot of progress has been made in recent decades.
We generally know how to construct buildings that satisfy the hazard spectrum, a design tool that accounts for earthquake risk in specific regions. Engineers also make design decisions based on building type. A nuclear power plant has to comply with more stringent standards than an office complex, for example.
These decisions are made to save lives, prevent costly damage and ensure that certain buildings, such as hospitals, remain operational after an earthquake.
"We're at the point that we can design a building at the appropriate safety and performance level," says Lau, "but the non-structural parts have been neglected for a long time."
Role of Suspended Ceilings
Non-structural elements such as suspended ceilings, along with electrical and HVAC systems, gas lines, communication cables and other mechanical features, are an essential part of a functional building.
If ceilings collapse, people might be afraid that a perfectly safe building is in jeopardy and run outside, where they can get in the way of emergency responders. This happened during the huge 2011 Tohoku earthquake in Japan, says Lau, who has travelled and collaborated with researchers around the world to assess the impact of quakes.
Improving the design of non-structural building components will not only minimize injuries, it will also reduce recovery costs and timelines.
"Our work can have a significant economic impact, especially for smaller earthquakes, which happen much more frequently," says Erochko.
"This is a way to support community resilience."
Internationally Significant Research
Carleton's simulation technology is the domain of Flude, who came back to university after a decade working as a structural engineer.
Typically used for flight simulators and other transportation research, this project is the first time it is being applied toward earthquake engineering, drawing interest from collaborators in Japan, Taiwan, the U.S. and other countries.
A full-scale building mock-up complete with suspended ceilings can be mounted on four "shake" tables, which can move horizontally, vertically and rotate. This allows the team to simulate how various floors of a building will sway during a quake, with advanced instrumentation tracking the movement of components in real-time.
The testing they're now doing intensifies incrementally from minor to major tremors, allowing the team to evaluate the structural properties of and damage to the ceiling throughout the process.
"We'll be able to see when panels pop out and fall," says Flude, explaining that while ceilings are the initial focus, other components could be studied next, and that the data they acquire can be applied toward enhancing design codes and upgrading existing buildings.
"Our overall goal," he adds, "is to help protect people, save money and make society more resilient."
