Issue link: http://digital.canadawide.com/i/493534
A PR IL 2015 | 21 Structural Steel PHOTOGRAPHY COURTESY SUPERMETAL STRUCTURES INC. & EMPIRE IRON WORKS LTD. seeing strong competition, so a big part of our focus is on cost competitiveness, espe- cially in industrial steel," adds Paul Zubick, COO at the Edmonton-based structural steel company Supreme Group. The drive for more interior light and space is pushing core-to-periphery spans in office towers to lengths of 12 and 15 metres today, compared to a decade ago when these spans were mostly in the nine metre range, says Sylvie Boulanger, VP of technical marketing at Supermetal Structures Inc. Increasingly, owners and developers of office towers want larger lobbies or atri- ums, "So steel columns must be interrupted with a truss that transfers loads from columns above onto the columns below," says Boulanger. "Our project at Eighth Avenue Place in Calgary required the use of a two-storey-tall transfer truss for a parking garage interrupting two 45-storey-tall columns." Eighth Avenue Place has 12-metre core-to-periphery spans allowing for large column-free open spaces. Also, more daylight is let in by having the columns in the corners of the building set back. Another Supermet al project is the Calgar y International Airport that entailed 17, 60-metre truss spans for a new check-in hall. "A few years back, instead of a 3D or triangulated tubular truss, a 2D-type truss with a couple of intermediate support columns might have been used," says Boulanger. The trusses were designed with skylights above to let more light in and help with pathfinding. A recent project for a student residence at the University of Manitoba required exposed full-storey trusses. The design concept for the Pembina Hall Residence expansion entailed a pair of 14-storey tow- ers, one at each end of the existing residential building, with sufficient strength to support a new 10-storey residential block above. Besides 36 rooms on each level, the new block would span 50 metres over the existing Pembina Hall. The structure rises just over 57 metres above grade, extends almost 80 metres in an east-west direction, and is only 13.3-metres wide. The solution to the project's challenging design concept included four parallel full- storey depth trusses per floor, with two interior ones hidden in corridor walls and two exterior trusses, fully exposed. This was done for each of the 10 floors. "With the trusses on this project, you needed to span over an existing building and respect tight tolerances," Boulanger says. The project received a sustainability award as the steel used addressed the need to densify vertically on campus. Boulanger, who has a PhD in structural engineering, says that the kind of extra heavy duty trusses used on the University of Manitoba project, and other projects with similarly robust support requirements, are more feasible today partly thanks to better 3D modelling capabilities, CNC equipment and availability of certain grades of high-strength steel. The Telus Garden office tower in Vancouver is another project making dramatic use of massive trusses with exposed elements. The 22-storey building includes a massive front entrance canopy with AESS and Glulam among other elements. On either side of this, four-storey cantilevered sections of the building extend above the adjoining streets. "There's a huge, 60-foot high zigzag truss for this section that goes out above two lanes of traffic over the street. It's the same on the other side," says Rob Third, president of George Third & Son. The shift to more AESS exposed the need some years ago for an assist such as the one provided by the CISC Guide for Specifying Architecturally Exposed Steel. In addition to technology and software, this can streamline the process from concept to completion. The guide was developed to facilitate better communication among architects, engineers and fabricators. The guide also serves alongside two other AESS documents – the sample AESS section of structural Steel Specification and the CISC Code of Standard Practice. "It was felt that visual references would help all parties understand the intent of the new AESS documents as applied to the design of structures," says the guide. Perhaps the heart of the guide is its category matrix. Each category represents a set of characteristics, which clarifies what type of work is to be done on the steel, the required tolerances and if a visual sample is needed. Selected by the architect, the categories appear on architecture, engineering, detailing and erection documents. Certainly, Boulanger, who co-ordinated development of CISC's AESS documents while at the institute, considers it crucial. "Categories are needed more today as the trend to AESS is pushing for them," she says. The clarity, precision and accuracy that the categories enable should save time and money, and prevent mistakes and help engineers, fabricators and other YVR West Chevron expansion, Vancouver International Airport; New check-in hall project, Calgary International Airport; Box truss erection, University of Manitoba. Eighth Avenue Place, Calgary, AB.