Bridge Building

Bridge Building

October 28, 2010
Former engineering student Andrea Mak ran a

Former engineering student Andrea Mak ran a series of tests on a steel culvert built in the Queen's University GeoEngineering Centre to help improve the strength and safety of the vital infrastructure.
Ian Moore

You’ve seen them, driven over them, walked through them, but you’ve probably never given them a second thought. Yet culverts — those corrugated steel arches buried under roads that allow rivers and streams, vehicles, people and animals to pass through — are a critical piece of infrastructure that were born out of Canadian ingenuity.

Invented in Canada in the 1950s, long-span steel culverts are undergoing a renaissance. With thousands of small bridges across North America aging, long-span steel culverts are the natural replacement because they are easier to build than conventional concrete bridges and cost half as much. And thanks to master’s research by former Queen’s University engineering student Andrea Mak, the new generation of culverts is better and safer than ever.

Working out of a CFI-funded testing facility at the Queen’s GeoEngineering Centre under the supervision of engineering professors Richard Brachman and Ian Moore, Mak oversaw the construction of a 10-metre-long steel culvert inside a three-metredeep test pit. After the culvert was buried, Mak tested its load-bearing capacity using a piston-like device (called an actuator) to press down on specially built frames that simulated the axles of a large truck. Mak measured how the pressure affected the behaviour of the culvert structure and the soil around it and then tested the span to failure —
something that had never been done in either a laboratory or a field setting.

Mak is just one of many talented graduates from the GeoEngineering Centre whose expertise is in huge demand. “In geotechnology, Canada punches way above its weight in terms of what we do internationally,” says Moore. “And how do you get good students to train? You have the best facilities in the world and professors who are the leading experts — and you get this kind of momentum.”

Mak’s project was a success on several levels. The Ontario firm that manufactures the culverts has used her test results to further improve its product and increase its market potential. Her data also enabled the creation of a 3-D computer model that allows culvert designers to accurately predict the strength of their structures under various soil and load conditions. Similarly, a set of design equations based on Mak’s numbers will eventually become part of highway- and bridgebuilding codes in Canada, the United States and around the world.

Today, Mak is a working geotechnical engineer in Vancouver and says her experiences in the Queen’s lab were invaluable for her professional life. “I use the skills I developed in the laboratory to better understand soil behaviour,” she says. “Knowing how loads transfer through the soil from that test has been a huge help to me in my modelling and design work.”