A four-story historic building on a tight lot in Toronto is about to have a 13-story building built on top of it. Seventy-foot delta frames made of tubular steel columns filled with concrete will be set at angles and will stabilize and support the taller building. Cast steel nodes -- weighing 35,000 pounds each -- will tie intersecting delta frames together. "With steel castings, you put the steel where it needs to be for the flow of forces on the structure. You are not confined to having to build up elements from plate," says Carlos de Oliveira, president and principal structural engineer of Cast Connex.

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