The detailing, fabrication and erection of about 1,700 tonnes of steel for the Ottawa Light Rail Transit (OLRT) systems Belfast Yard Maintenance and Storage Facility (MSF) and galvanized train shed hardly qualifies as a big job by Walters Inc.’s standards.
By comparison, Walters is fabricating 25,000 tonnes of steel for a potash mine in Saskatchewan and it has a similar sized contract in New Jersey.
"But every job comes with its own challenges," says Sam Barrett, project manager of the OLRT job for Walters. "You always have to be prepared, and whether it is 10,000 tonnes or 1,000 you still have to co-ordinate a wide variety of activities before the client’s drawings materialize into the steel erected on site"
At the OLRT, the steel company’s contract called for the labour, material and services for supply and installation of structural steel, steel roof and floor deck for the maintenance and storage facility. The facility is made up of five areas: a two-storey section for offices and maintenance and storage areas with low, mid and high roof spaces. The 200-metre-long train shed is northwest of the main building, says Barrett.
Both buildings were engineered with a combination of moment and simply supported (braced) frames.
"In the north/south direction the structure makes clever use of moment frames (a system of columns and beams that are connected to one another with fully and/or partially restrained moment connections). This is the logical choice when large, open spaces are desired," Barrett says, adding that it "was a must" to allow for easy train movement.
In the east/west direction, where space was less critical, the structure uses simply supported, braced frames/shear walls without comprising the space, he says.
The fabrication and erection of moment frames is "more involved" than simply supported, braced frames because moment-frame column and beam sizes tend to be heavier due to their means of transferring forces. Their connections tend to require larger connection plates/doublers and bolts, leading to more work in the shop and field, says Barrett.
The fast-track steel contract, from August to mid-December 2014, was done by a Walters’ crew that peaked at 29. Site Superintendent Leo Guay has been responsible for the site co-ordination of numerous high-profile projects in the Ottawa area, including the rejuvenation of the West Block Parliament buildings, he says.
The OLRT project was modelled in Tekla Structures software. Throughout the design and detailing phase progress models were provided to the contractor to incorporate into a centralized BIM (building information modelling) model to check for, and mitigate interferences with other trades prior to commencing fabrication, says Barrett.
"Before we had BIM or any form of co-ordination in software, those issues (interferences) would have been discovered on site at the time of erection…often a more costly fix."
Of the 1,700 tonnes of steel, about 1,100 tonnes made up the maintenance and storage facility, 300 tonnes for the train shed and the remainder (580 or so open-web-steel-joists) for the buildings. The longest steel elements — W1000s — were about 24 metres by a metre deep.
Barrett says that a key to completing the project on time and budget was the cooperation and collaboration between the respective site and design teams.
"It allowed for a fast and appropriate response to any challenges that arose."
The project’s engineer was the MMM Group Ltd.; Canam Group Inc. supplied the open web steel joists; and Ideal Roofing Company Ltd. Manufacturers provided the steel roof and floor deck.