Elevated Floor At Durham College Is A Steel Engineering Challenge

Durham College’s new student services centre makes a striking image on the Oshawa campus. A portion of the building is elevated on long concrete columns giving the appearance of table legs holding up a table top.

“It is more unusual than most jobs” partly because of the tight schedule and largely because of the “creative design,” says Chris Palin, partner with CPE Structural Consultants Ltd., structural engineers for the job.

Steel was selected over concrete for the structure of the building because of economics and the unusual shape which features a 15-by 35-metre section of the new centre raised on five- to eight-metre columns above grade, says Palin.

A 10-metre-wide utility service trench below the building had much to do with the building’s elevated floor design. Few buildings are constructed over top of underground utility corridors because it limits accessibility to the servicing corridor, says the structural engineer.

There is also the danger that in an emergency, if a watermain bursts, for example, water could flood the occupied space above it.

The elevated floor — which rests on 23 columns — was a steel engineering challenge. It consists of a steel deck with concrete slab supported by steel joists and beams. The steel frame of the raised floor has an irregular beam layout in the section directly above the service trench.

“With the service core running askew through the site we couldn’t really pick a regular framing pattern to use for the whole building,” says Palin.

As a result, some of the steel members span up to 50 feet and are 32 inches deep.

The steel beams and joists were sized carefully to meet vibration criteria, he points out. Such long spans are unusual in conventional designs which generally incorporate close column spacings for economy, Palin adds.

“Concrete wasn’t an option because the height of the floor off-grade would have made it difficult to form.”

The steel design is “very different” from traditional designs. Normally, a system of beams is set at 90 degrees to each other, but because the utility corridor below the building is offset by 30 degrees to regular framing, cantilevers and skew framing were needed to complete the span, explains Palin.