October 10, 2012

PCL CONSTRUCTORS INC.

The 1.6-million-square foot Humber River Regional Hospital includes an innovative concrete structure made possible through the above raft slab concrete pour shown above.

New Humber hospital features innovative concrete

DAN O’REILLY

correspondent

An aggressive schedule, a targeted 30 per cent recycled content in the cement and massive concrete pours including a continuous 13-hour one are just some of the construction dynamics of the 1.6-million-square-foot Humber River Regional Hospital.

Located on an infill site directly across from the Ontario Ministry of Transportation headquarters on Keele Street in Toronto, the approximately 200-metre-long complex is comprised of a 15-storey tower and two six-storey podiums.

The most innovative feature of the concrete structure is the lack of construction joints, says Kathryn Edwards, associate with Halsall Associates, the structural consultant and member of the Plenary Health Care Partnerships, the private consortium which is developing the $1.75-billion acute care hospital under a 30-year concession agreement with the province.

“Buildings as long as this one would typically have expansion joints or pour gaps to allow shrinkage of the concrete.”

Instead, the engineers and builders have implemented a system of temporary contraction joints which will be left in the floor structure to allow the shrinkage of the concrete to occur over several months after which the joints will be connected to complete the floor diaphragm.

The podium is separated into nine slab areas and the tower into three slab areas which eliminated “the need for costly expansion joint hardware.”

There are also a number of other design and construction features which distinguish the hospital from other similar large-scale projects, she says.

A case in point is the use of two different foundations systems — a raft slab for the tower and 5,500-mm-wide strip footings for the podiums.

The raft slab was chosen because the bedrock below the tower is more than 30 metres below the basement elevation. As for the wide-strip footings, they are only supporting six storeys “as opposed to the tower which is 15 storeys tall and therefore heavier.”

The size of the hospital and speed of construction are also notable, says Edwards, pointing out that all of the concrete will be poured in a short 14-month period, from May of this year to June 2013.

For PCL Constructors Canada Inc., the construction arm of Plenary Health, the combination of the size, speed and design have required and are requiring major logistical planning and co-ordination with its subtrades and concrete supplier Innocon.

From the last week of March to early May, the company organized three massive concrete pours of approximately 4,000 cubic metres each to build the 180-metre-long, 40 metre-wide and 1.8-metre-deep raft slab under the tower footprint. The longest lasted 13 hours, says general superintendent Dean Xuereb.

Managing those pours was not difficult, but it did require an early Saturday morning starting time and that, in turn, meant that municipal approvals had to be obtained, and trucks, manpower, and other services had to be in place. Eighty trucks from four different plants delivered the concrete.

“It started with a 3 a.m. debriefing of all PCL staff to ensure placing and materials managers were ready. Constant radio communication was vital but in most cases for the three pours we met all our objectives.”

The challenges continue, Xuereb says.

With eight tower cranes and four placing booms on site, there is constant co-ordination to ensure there is always enough concrete.

Approximately 2,500 to 3,000 cubic metres are trucked to the site weekly.

“We advise Innocon weekly of our expectations.”

Approximately 400 workers are on site, but that figure will most likely increase to 1,200 when the project hits its peak at the beginning of 2014, says Xuereb.

Construction started last fall and is expected to take until 2015 to complete.

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