Building Rehabilitation in Montreal
December 1, 2007
By Canadian Consulting Engineer
Groupe S.M. were structural engineers for the seismic rehabilitation and expansion of two buildings in Montreal's International Quarter. The Montreal Herald building was converted into an office for f...
Groupe S.M. were structural engineers for the seismic rehabilitation and expansion of two buildings in Montreal’s International Quarter. The Montreal Herald building was converted into an office for for Socit Immobilire Camont, while the former Bank of Canada building adjacent to it was converted into an upscale Hotel W SITQ.
Though the projects were for different clients, the renovations were completed simultaneously. Also, a new glazed courtyard was added to connect the two buildings.
Located on the corner of St-Antoine and McGill, the Montreal Herald building dates back to 1915. The seven-storey building was originally used by a printing company, the Herald Press. Its main structure is composed of reinforced concrete rigid frames. The floors are thin slabs resting on reinforced concrete beams, with 4.42 x 5.50 metre columns.
The Bank of Canada building, built in 1950, originally had six storeys. Its structure is steel coated with concrete, with structural concrete floor slabs. In 1974, a steel structure was erected for two additional floors. When the new project was launched in 2001, the building had been empty for 10 years and was deteriorating.
The Montral Herald had an important architectural value due to its facades and the Bank of Canada was valuable solely for its structure. To address the complexities involved in restoring the structures, the help of university researchers was enlisted. Composite materials still under development were required and a spectral dynamic analysis and a finite element analysis were performed.
The rehabilitation needed to increase the buildings’ useful life to more than 50 additional years while achieving the safety levels of a newly constructed building.
In the last 25 years there has been an evolution of the seismic criteria in Canada, so for example, the buildings’ existing paraseismic cross-bracing did not meet current requirements. To bring the buildings up to National Building Code, the engineers had to exercise ingenuity and pay attention to detail. In the case of the Bank of Canada, the columns and existing steel beams had to be married to the concrete walls, ensuring the continuity on each floor. For the Montreal Herald, the engineers had to ensure that the existing floor slabs could adequately support the transfer of shear forces towards the new walls.
Montreal Herald facade
Several conservation techniques were used. Most important was the use of a concrete grout, which was applied by pressurized injection into special waterproof frameworks for windows and other openings.
This approach provided an almost perfect cohesion between existing and reconstructed surface materials, allowing for the architectural finishes to be seamless.
Cross-bracing and edge beams also had to be added to support and preserve the buildings facades. Their integration required special reinforcement at the coupling beams.
Concrete columns in Montreal Herald
A system of bearing walls was designed to integrate the existing columns. These columns required much restoration. Many methods were used, including the use of composite materials such as carbon fibre to conserve their structural integrity. The use of composite materials was often the singular choice since the building had, over time, been renovated and the construction methods and the plans were not available.
A continuous review of the restoration process had to be done as the demolition unveiled a plethora of deteriorated conditions, such as mislaid granulated concrete and the use of non-traditional reinforcements, such as tie rails and square bars.
The new architectural design elements further complicated the structural engineering challenge. For example, two floors had to be opened up for the insertion of a monumental staircase. This required the splicing of columns and caused the floor diaphragms to lose stability. Once again, composite materials were applied to the slender columns in order to compensate for the lack of steel overlap and carbon laminates were applied to the floor beams.
Addition of glazed walkway
One of the most noticeable changes brought to the area is the glass-enclosed courtyard that was inserted between the two buildings and is shared by them. The design was a challenge because one building has a concrete structure and the other is steel, requiring an additional seismic analysis as to the buildings’ behaviours. It was decided that the glass roof should be attached at the Bank and remain mobile at the Montreal Herald building.
Montreal Herald & Hotel W — Structural engineer: Le Groupe S.M. International, Montreal (Jacques Guertin, ing., Yves Levesque, ing.)
Montreal Herald — Owner: Socit Immobilire Camont. Architect: Beique Thuot Legault. Contractor: Anginov
Bank of Canada/Hotel W — Owner: SITQ. Architect: Lemay & Associs. Contractor: Decarel Construction Management