Award

Caminus Photography / courtesy norr architects and planners Centre 10 The reinforced steel is near completion. wo previous starts had been made on planned high-rise condo towers at the location of a former retail strip in Calgary when Centron acquired the property in July 2011. The site had already been excavated and seven levels of underground parking for 736 vehicles constructed. The first and second floor slabs were also in place. Instead of twin condo towers, Centron changed the concept and opted for a single 10-storey building, designed to a LEED Silver standard, with 335,000 square feet of office space and 20,000 square feet of retail space. "We felt the timing was right for an office building at the location," says Richard Heine, executive VP at Centron Group of Companies. "The parkade already in place was a consideration. It can often take a year to build the parkade, so it allowed us to target the fourth quarter of 2013 for occupancy." The switch from dual towers to a single office building for Centre 10 entailed a considerable amount of structural redesign. There were three main components to this. A new elevator core – to serve the 10 office floors from a T Centre 10 p44-49Centre10.indd 45 centrally-located main lobby – replaced elevator cores at the east and west ends of the site. To support this new load, an extensive raft footing, 12 feet deep by 42 feet square, was required at the lowest parkade level. "The existing slab on grade had to be removed and the grade excavated to accommodate this massive footing. There were approximately 700 cubic metres of concrete pumped into the footing alone," says Heine. Because the central elevator core starts at the main floor, the crash slab, or pit of the elevator core, is suspended just below the P1 level of the parkade. Heine notes that this too is also a massive transfer slab, about six feet thick and 36 feet square. The slab is supported by shear walls on each parkade floor up to P1. The walls are, in turn, supported by the central elevator core's new raft footing. Other critical structural changes had to be made. Originally, the central area of the site, which would have sat between the two towers, had been designed for a four-storey podium – not a 10-storey office building. Footings and columns for the area had to be upgraded. courtesy centron group of companies by Godfrey Budd "The existing slab on grade had to be removed and the grade excavated to accommodate this massive footing. There were approximately 700 cubic metres of concrete pumped into the footing alone." – Richard Heine, executive VP, Centron Group of Companies "Columns had to be reinforced by adding concrete dowelled into the existing columns. The existing footings were reinforced by the use of micro piles installed through the footings," says Heine. The third main component of the structural redesign involved the removal of several concrete columns at the main floor level in order to open up the main floor and lobby area. Heine says that, in common with the central core redesign and modifications, this work involved extensive engineering and construction, in part, because loads october 2013    /45 13-09-13 3:43 PM

• Cover