Innovative steel castings, which provide high performance earthquake resistance while also enabling unprecedented architectural designs, are being used successfully on several major projects in the United States and Canada.
The solution has been developed by Cast Connex, a successful spin-off of graduate research undertaken by University of Toronto Engineering alumnus Michael Gray in partnership with Carlos de Oliveira.
The company was given a kick start by the Heffernan Commercialization Fellowship, which enables graduate students to transfer their research into successful businesses.
The steel castings are made by pouring liquid steel into moulds, then letting it cool into a solid. The most recent iteration resembles a small ladder with fingers between the rungs. The connectors are installed at the end of a diagonal brace member that spans from one building level to the next. The fingers transmit the brace load via bolts through their ends. If an earthquake strikes, the fingers are deformed in flexure, absorbing earthquake energy so the building doesn’t have to.
The technology is suitable for both new builds and retrofits.
“What we do is unique because casting has been used for mechanical applications for a long time, but we’re among the first to use it in structural engineering. It’s attractive because of its potential for free form geometries, meaning you can construct non-traditional designs and unlikely angles,” said Gray.
Weld fabrication is the traditional building construction method used, and it sees support beams cut from large mass-produced steel plates and then welded together, which restricts the architectural possibilities. It is also a challenging fabrication process when designing for the devastating effects of earthquakes and is not the ideal approach for remote areas where tools and expertise are limited.
After the devastating 2010 Haiti earthquake, which displaced around 1.5 million people, Cast Connex donated its steel castings to enable the construction of an earthquake resistant school in Port-au-Prince, as part of an industry-wide coalition to prepare the island nation for future natural disasters.
From an architectural perspective, the Queen Richmond Centre (QRC) in Canada is one project benefiting from the brace system aesthetically and structurally.
“The connection joints that make the Xs at the QRC so distinctive also makes them virtually impossible under the restrictions of traditional construction techniques,” said Gray.
This custom casting technology opens the doors for shifts in the architecture of new buildings, creating opportunities for never before seen structures.
The first major projects using the technology developed in Gray’s doctoral research are the Audain Art Museum in Whistler BC, and a retrofit for the St. Aubin High School in Baie-Saint-Paul, Quebec — the site of one of the worst recorded earthquakes in Canadian history.
They have also started several major projects in the United States, including the TransBay Center in San Francisco, CA and a new retractable roof for the Arthur Ashe Stadium in Flushing, New York.