By Perry J. Greenbaum
Buildings: Montreal Convention Centre ExpansionEngineering
Approaching the expanded Palais des Congrs de Montral on Bleury Street from the west, one comes across an impressive rainbow-coloured glass wall, twice the size of the original grey concrete facade....
Approaching the expanded Palais des Congrs de Montral on Bleury Street from the west, one comes across an impressive rainbow-coloured glass wall, twice the size of the original grey concrete facade. The transparent exterior is not only a remarkable aesthetic feature, it also gives passers-by an expansive view inside the three-storey space.
Leave it to Quebec to do things in a distinct way. When the Quebec provincial government announced plans a few years ago almost to double the size of the convention centre from 70,200 square metres to 133,000 square metres (1,431,500 s.f), it set some ambitious conditions for the project. A consortium of three large engineering and construction firms known as GESPRO-BFC-Divco led by Ali Ettehadieh, ing. were commissioned for a design-build project of almost $250 million. Gespro is a subsidiary of engineering firm Gnivar of Longueuil, Quebec.
The fast-track approach made the project a memorable experience for the engineers. “All the steps were done simultaneously, making this design-build approach completely different from conventional projects,” says Robert Lamoureux, ing., director of the mechanical consulting team at Gnivar. Gnivar were in charge of project management and shared the mechanical engineering role with Pageau Morel & Associates. Pageau Morel also did the electrical engineering, and Dessau-Soprin were the structural engineers. “We were starting construction while we were working on final design plans,” says Lamoureux. Moreover, the convention centre had to remain open during 15 months of work.
The massive construction site, bounded by de Bleury Street to the west, St. Urbain to the east, Viger to the north and St. Antoine to the south, posed a number of difficult engineering challenges soon after work began in earnest in the spring of 2000. For one thing, the design preserved the facade of a number of heritage buildings adjacent to the construction site. As Ettehadieh notes, “One of the principal attractions of Montreal as a convention destination is the historic nature of its architecture.”
The number of loading docks for trailer trucks was increased to 18 from five, and the underground parking garage was expanded to hold 1,200 cars (half under the convention centre and half under de Bleury and a new CDP office building). In addition, the new wing of the convention centre had to be built before modifying the old section.
No part of the project was more challenging, however, than turning a 300-metre section of the Ville Marie Expressway from St. Urbain to de Bleury into a tunnel. It necessitated the design of a sophisticated ventilation system to exhaust fumes from the newly covered expressway. And, of course, the effect on traffic was predictable; drivers faced lane closures on one of downtown Montreal’s busiest arteries for about six months between April 2000 and September 2000.
Sitting pretty over the Ville Marie
Serge Vzina, ing., vice-president of engineering (special and large-scale projects) at Dessau-Soprin of Laval, describes the structural challenges in the project. As Vzina puts it, “The key word for this job was ‘existing condition.’ The project had to be adapted to what existed beforehand. It required a lot of adaptability in our design.”
Part of the original convention centre straddled over the 33-year old Ville-Marie expressway on drilled caissons. Today, the expressway runs underneath the expanded convention centre, forming a sturdy foundation.
The eight-lane expressway runs approximately 10 metres below street level. It forms a 42-metre wide open trench separated by a median that acts as a barrier between the east and west bound flowing streams of traffic.
Vzina explains that to close up the expressway at street level required the construction of drilled caissons of 0.9-meter to 1.2-meters in diameter along its north side. The caissons support a 1.8 metre deep cast-in-place reinforced concrete girder, which acts as a continuous support.
The existing central median, as well as the south side retaining wall of the expressway, had to be partially demolished and extended in height in order to form the central and south end supports of the two 21-metre span continuous structural system used to enclose the expressway.
Once these supports were in place, precast and prestressed modified T-shaped AASHTO type IV beams 21-meters long were installed and form the deck closing-up the expressway. The design live load was 7.2 kPa (150 lb/ft2). The modified T-shaped AASHTO beams are inter-connected with shear plates to form a diaphragm. They are anchored to the south side retaining wall of the expressway and simply supported on neoprene pads at the central support (median) and north support (1.8-meters girder on caissons). The result was a 42-metre span of concrete exposed to thermal variation that could range from –30C to +30C.
Such a long span led to thermal displacements (expansion and contraction) that could reach 25 mm to 30 mm and had to be accounted for. Another critical loading condition was that the deck has to support a relocated fire station.
The deck is protected with a waterproofing membrane and a minimum of 75 mm of rigid insulation. A 125 mm concrete topping covers the rigid insulation and acts as the floor slab.
Besides supporting the deck, the extended median seals off airflow in each lane. This is a crucial safety factor, allowing the ventilation system on each side to push air in the same direction in which the traffic flows.
Lamoureux explains that to ventilate the tunnel, nine axial flow fans were installed in the tunnel’s new mechanical room, producing an airflow of 1.4 million cubic feet per minute (Cfm). Each fan is equipped with a 200-hp motor. The job had many challenges, Lamoureux says: “When we quoted the project, Transports Qubec had not yet defined such criteria, mainly because it was design-build. Still, [they] were fully satisfied that the mechanical systems met high standards.”
For example, the provincial highway authority mandated that the floor covering the expressway had to act independently from the surrounding retaining walls. “We had to develop a concrete-block anchorage system for the floor,” Vzina pointed out. “So even though the floor sits on the south retaining wall gravitationally, both thermally and seismically, it acts independently from it.”
The roof of the covered highway was also designed to support a 300-tonne super-crane, which became, as Vzina put it, “the only working platform [from which] to build the west-side extension of the convention centre.” This distinctive facade, an 80-metre extension from the existing facade, consists of transparent multi-coloured glass with an art installation in the upper corner.
The expanded convention centre, built to hold about 20,000 people, was designed to meet ASHRAE Standard 62-1999 for indoor air quality, 15 or 20 cfm/person of fresh air, depending on the type of occupancy. The mechanical and electrical engineers had to boost the heating and cooling capacity of the existing HVAC systems. The total airflow, which stands at 3.5 million cubic feet per minute (cfm), is managed by multiple systems of various capacities.
Lamoureux explains that the pre-expansion convention centre held both heating and cooling plants in a single room, but it was not large enough to accommodate the expanded services so they kept the existing room for the heating plant, and built a new cooling plant at the opposite end of the convention hall. The cooling plant accommodates four centrifugal chillers, using HFC-134A refrigerants. Three are 1,000 tons capacity, and one is 500 tons. (An air-cooled chiller located elsewhere provides cooling to critical computer systems in emergency situations). Chilled water is supplied at 42F and is available all year long by the the use of a winterized cooling tower coupled with an inside water reservoir of 10,000 gallons. For heating, two gas-fired 600-bhp boilers have been added, thus increasing capacity to 2,000 bhp.
As an energy conservation measure, most of the systems are equipped with
carbon dioxide sensors, which are able to regulate the flow of fresh air into the systems. The other main energy conservation measures are the use of closed-loop run-around energy recovery systems between fresh and exhaust air, the diversion of exhaust air from the meeting and exhibition halls to the loading docks and parking areas before it is exhausted outdoors, and the use of variable speed drives in many ventilation systems and pumps. The goal is to achieve an annual energy consumption of 900 MJ/m2 or 23 kW-h/s.f. over the entire building. Actual results are still to come.
Exhibition space and loading
On exhibition level 22000, the floor consists of a concrete composite surface, again on pre-stressed AASHTO Type IV beams, 25 metres in length.The long beams create an open airy exhibition space and the surface can bear the standard load of 17 kPa, or 350 lb/ft2. As it stands, “45-foot trailer trucks can drive from the loading docks right on to the convention floor,” Vzina says.
At the old loading docks, trucks would sit idle on St. Antoine Street, double parked and impeding traffic. In addition to the new 18 loading stations on the second floor, there is a waiting zone for trucks on the ground floor beneath the loading area. Trucks exit through the Tramways building on St. Urbain Street.
The design-build approach led the building of the 4 1/2-storey underground parking garage, which can hold 650 cars. Traditionally, one would excavate the site, build the underground garage and work up to each level. “We couldn’t afford the time to do things that way,” Vzina says. “So we decided to build the first storey of the Palais at the same time that we started excavating the underground section, using a top-down construction method. The ground floor was the junction. There were two teams — one going up and one going down.”
To be sure, the design-build approach is pretty rough on the engineers, stretching their imaginations. However, as the project winds down, scheduled for completion in May 2003, Lamoureux sums up the sentiments of the engineers who worked on the new Palais: “I asked to be involved with this project, and I’m glad that I did.”
TRACKING THE EXPANSION PLAN
The Ville Marie expressway was enclosed from de Bleury Street to St. Urbain Street, about a 300-metre stretch. Five covered passageways (two outdoor, three indoor) were built north-south. The intention is to re-establish links between Old Montreal and the city’s business core.
Along the south side on St. Antoine Street, three Montreal landmarks were integrated into the convention centre: the Tramways Building, an Art Deco design, was preserved; and the facades of two heritage buildings were incorporated — Fire Station No. 20, dating to the early 1900s, and the Rogers and King Building, a foundry built in 1885.
The expansion to the west included the demolition of existing buildings on de Bleury Street and St. Antoine to expand the building. De Bleury is now the official entrance to the convention centre, facing the International District.
URBAN DESIGN: BREATHING LIFE INTO AN OLD AREA
The convention centre expansion forms part of the Quebec government’s plan to boost tourism in Montreal. Although the city ranks third in North America, after New York City and Washington, D.C., in attracting trade conventions, the Quebec municipal affairs office wanted to solidify its position. Since its opening in 1983, the Palais des Congrs has held more than 700 conventions, attended by more than 1.7 million people.
The convention centre resides in what is known as the International District, a rejuvenated area that sits between Old Montreal and the downtown core. Another prominent building in the area is the neighbouring Caisse de Dpt et Placement du Qubec (CDP) financial office complex. As well, new public areas will be open this spring. Victoria Square has been refashioned, and there is a new square — Place Jean-Paul Riopelle — situated between the convention centre and CDP building (Gnivar is doing the civil and infrastructure engineering for the new public space).
Another new garden (see photo) has been created north off the Viger Explanade that cuts east-west through the complex, making a connection with the Chinese Quarter. The park has grassed earth berms linked by stone pathways and blossoming crabapple trees in the tradition of Montreal’s public squares.
Pageau, Morel and associates, the electrical consultants, have designed all the lighting systems with energy efficiency and flexilibity in mind. In the exhibition hall, for example, which is twice the original floor area, there is a 50% reduction of the watt per square foot load without compromising the lighting levels. The new industrial overhead fixtures are spaced every six metres, and each has four T-8, 32-watt fluorescent tubes, and electronic ballasts with a ballast factor of 1. The total load is 132W, whereas in the old lighting system lights were spaced at three metres, and the total load was 240W. Other energy efficiency lighting measures include occupancy sensors in the meeting rooms, and centralized and local controls.
A new building automation system (BAS), to which the existing control points were added, is linked with the main lighting control, access control and fire detection systems. Totally computerized, the BAS has internet capabilities for remote control and interacts with components such as CO2 detectors and pressure gauges to maintain environmental conditions based on actual occupation levels. There is a completely new addressable fire alarm system and a centrally controlled security system overseeing 860 doors (80 different types) and 100 CCTV cameras.
Two 1250kW/1562.5kVA emergency generators operate in parallel. They are sized to service the kitchen equipment and one chiller. Thus a power shortage in the morning will not jeopardize the success of an evening banquet.
The communication systems has 3,500 telephone outlets and 3,500 internet outlets. They are connected with optical fibre cabling from the server to each hub, and category 5E cable from hub to outlet. The system includes video projections that can be performed throughout the complex and projected onto giant screens. There is also simultaneous translation and videoconferencing.
Perry Greenbaum is a freelance writer based in Montreal and New Hampshire.
Owner: Palais des Congrs de Montral
Design-Build: GESPRO-BFC-Divco (Ali Ettehadieh, ing.)
Structural: Dessau-Soprin (Serge Vezina, ing.)
Mechanical & electrical: Pageau, Morel et Associs (Michel Carpentier, ing.) and Gnivar (Robert Lamoureux, ing.)
Architects: Saia et Barbarese, Tetreault, Parent, Languedoc, Aedifica
Photographer: Paul Labelle
Suppliers: Carrier (chillers), Trane (chillers), York International (ventilation)