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Creating a design that is the first of its kind in the country is a daunting task, but building the second of its kind is only so much easier. Nevertheless, EllisDon is the contractor to take on projects with this level of complexity, so it comes as no surprise that the construction manager is handling the building of Ed­monton International Airport’s Com­bined Office Tower (COT) project.

The COT will be a 130,000-square-foot, 10-storey structure that will provide improved airside ground operations, expanded retail service, extend the central baggage area and provide a new airside office and air traffic control tower. The project broke ground in March 2011 and will be completed in July 2012 for $70 million.

Construction will take place between two operating gates for boarding aircraft simultaneously with major renovations to the central hall and the pre-board screening area, according to EllisDon. The project will be delivered in phases to avoid interrupting operations of the airport, which has 6 million passengers pass through it annually.

According to EllisDon Senior Project Manager Cara Lochhead, the 130,000-square-foot structure will use a core system that has been constructed only once before in Canada.

The tower – designed by DIALOG – calls for a shear wall system for the core of the structure. This structure will meet post-disaster criteria, which is part of the reason for the shear wall design. The building is constructed in such a fashion that it is designed to be able to lose column supports and still stand.

As reported by Daily Commercial News and Construction Record, this type of system is ideal for fast-track projects like COT. The two tower cores are each a 1,625-ton system consisting of numerous prefabricated steel plate components that are stacked upon each other on-site. All columns and floor framing are uniquely arranged to tie back to the two cores to comprise the buildings’ basic floor plates. From the main floor beams at the perimeter line of the building, moment connections have been developed to carry an added cladding/glazing rail assembly to which the building envelope line, stick-framed glass and cladding assemblies are attached.

The exterior of zinc panels and triple-glazed strip windows was designed to give visiting passengers a view of Edmonton as they arrive and depart from the second-largest city in Alberta. EllisDon says each section of zinc panels is uniquely moulded to avoid impeding downward viewing angles as well as to reduce solar gain, while giving the building an overall “organic sense of shape and flow.”

Complex Challenges

Not only is the exterior skin aesthetically pleasing, it is incredibly difficult to construct. The building has complicated geometric angles that are far different from traditional stick-built structures. There are multitudes of doubly curved surfaces that converge together as well as tie back to planar window mullions. The challenges with bending analysis and the limitations of materials to physically be manipulated into these shapes has proved extremely challenging.

To circumvent any problems with this design, EllisDon has hired 3-D modeling company Gehry Technologies to plan the building envelope’s cladding and glazing. “It has an extremely complicated geometry to the exterior skin, so it is not a standard curtainwall system at all,” Senior Project Manager Cara Lochhead says. “We’re hanging strange 3-D shapes cladded in zinc between all this heavy-duty structural steel.”

Along with the challenges of the curtainwall system, EllisDon and the construction team had to work within a confined space surrounded by many passengers. There was limited lay-down space for materials, so EllisDon had to plan logistics meticulously.

“The biggest challenge is actually building our structure into the live airport,” Lochhead says. “That has been a puzzle in terms of logistics and has governed much of the planning on the site to date.”

Part of the challenge is the small footprint and the unique equipment utilized for installations to the exterior. Fraco platforms have been planned to handle the installation of the exterior fitments, including glazing, building envelope and zinc cladding. Given the irregular shape of the building with cladding sections protruding out – sometimes in excess of 2 metres from the line of the glazing – a top-down installation of the cladding system is required because there would be no means to bring a lift up and past a section installed below. Hence, while contractors build from the bottom-up for interior fit-out, everything else is added to the structure from the top down in terms of the exterior of the building.

“We’re using lifts on the backside of the tower sitting on the retail roof (level 4) as the tower is partially built in to the existing airport,” Lochhead says. “The front of the tower free-stands on the ground with the west stair core being the only part of the tower until level 4, at which point it bridges back to the retail roof elevation.”

To mitigate issues with logistics and operational impacts to the airport, EllisDon was heavily involved in the building envelope design as early as September 2010. While difficult, this challenge was eased somewhat through the use of 3-D modeling.

“The main way we’ve attempted to cut costs and maintain controls in the project was to fully develop and rationalize a 3-D model of the building structure and subsequent exterior components,” Lochhead says. “If we don’t go through this process and model the whole thing, we would have had escalating costs because of the lack of major controls. We have had so many more challenges and work than people anticipated; we wanted to control the design as much as possible to set parameters.”

Extra Baggage

One of the most challenging aspects of any airport project is usually found in baggage handling systems. EllisDon is working in conjunction with a separate general contractor, Vanderlande In­dustries, to handle this aspect of the project. EllisDon must work closely with Vanderlande Industries because of the sensitivity of the footprint where the system will be erected. Lochhead says special consideration must be taken to ensure Vanderlande avoids piping and ductwork that is key to keeping the airport operational throughout construction. Any piping, ductwork, electrical installations and existing structural elements that cannot be avoided have to be relocated to keep the airport live.

“There is a slew of stuff to reroute and get out of the way, so we made conscientious decisions with what was installed to ensure it did not conflict with what we were installing at a later date in terms of baggage lines,” Lochhead says. “We’re ensuring all piping and ductwork is out of the way as we demo into the existing airport. The tricky part is the new baggage system runs through existing major mechanical and electrical services, so we have a very big challenge ahead of us with an aggressive date to get the baggage system online.”

Constructing Canada

EllisDon was founded in 1951. Today, the company has capabilities in design/build, construction management, project management, health and safety consulting, pre- and post-construction services, civil construction, equipment sales and rentals, engineering/R&D, general contracting, public/private partnerships, equity services, facilities services, interiors and communications infrastructure.

EllisDon’s largest market is public sector institutions, and it is the largest healthcare builder in Canada. The company conducts 85 to 90 percent of its work in Canada, but it also has offices in Dubai, United Arab Emirates; Atlanta; Orlando, Fla.; and Athens, Greece.