Pavilion Pierre Lassonde brings a new architectural coherence to the Musée national des beaux-arts du Québec (MNBAQ) and enables the exhibition space to be increased by 90%. Designed by OMA and developed jointly with Provencher_Roy, the pavilion, with its entrance on Grande Allée Boulevard, gradually decreases in height while moving away from the urban hustle and bustle, creating a cascading effect that allows the museum to extend into the park on one side, while being open to the city on the other.
AESS4 was the steel of choice for the structural construction given the challenges which the engineers were facing, since this material allows a multitude of sections to be assembled to obtain an ultra-precise construction with a finished look with perfect lines. The building’s foundations and basement were built in the summer, and the framework, which required 1,200 metric tonnes of steel, was completed in the winter, which sped up construction.
To evoke the city’s penetration under a “pulled up” section of the Plains of Abraham, the third level had to extend as a cantilever (span of 20 metres x 25 metres wide) above a large hall surrounded by a 13-metre-high glass wall. The structural engineers managed to create this effect by using giant steel trusses. To limit deflections inside the structure, truss height was greater than the distance between the roof and the floor. The floors and roof consist of a large-span secondary frame supported by the top and bottom chords of the main trusses.
To have the structure make a spectacular contribution to the architectural expression of the pavilion, one of the two main cantilever support columns was pushed toward the inside of the building, which required a transverse truss to offset the front support load. The number of columns in the pavilion was significantly reduced due to the huge spans and the play of the multiple cantilevers. This was possible due to the steel trusses that are as high as the floors and where the diagonal members are part of the general bracing system. The use of joists and trusses also allowed all the mechanical elements to be inserted through the diagonal members in order to obtain high clearances.
Since the pavilion is made up of glass walls, not only did the deformations caused by the gravitational, seismic and wind loads had to be very closely monitored, but also those caused by the construction assembly stages. This is why the two cantilevers were built with precisely calculated camber. The structural engineers then closely monitored the situation as the dead loads were added so that the structure would not touch the glass wall and remain within the specified range. The monumental staircases also represented a sizable challenge since they had to be vibration--free. The building meets the mechanical performance requirements for LEED certification.