Award of Excellence: Eaton Building Redevelopment

CATEGORY: BUILDINGS

PASQUIN ST-JEAN & ASS.

The Eaton building on Ste. Catherine in downtown Montreal is a vast structure of over one million square feet distributed over 10 levels and two basements. The building, whose frame is part metal and part concrete, was originally built in 1925 and was expanded in several stages.

The new concept maintains the first four floors for retail uses, occupied by a major tenant named “Les Ailes de la Mode” and by other boutiques. The upper floors are now used for office space.

Structural engineering consultants Pasquin St-Jean & Associates of Montreal had to adapt to the great number of different situations found throughout the building. The major architectural constraints, such as the limited height for new structural elements, column spacing and unusual geometry, made this project a daunting challenge.

One of the most difficult aspects was the creation of a large atrium with a glass roof in the interior of the building. The atrium’s egg-shape form required the use of sizeable cantilevers, but the design had to take into account the limited ceiling height for installing structural elements on the one hand, and on the other hand the limited raising capacity of a tower crane installed on the building’s roof.

Deficiencies in the concrete structure were discovered only as the interior started to be demolished. The reinforcement of this structure therefore had to be done while minimizing intervention time and costs. Installing transfer beams, some of which made it possible to cut columns supporting nine floors, required very special work. A beam pre-bending process had to be devised to prevent excessive deflections when cutting the columns.

Actually, all the interventions related to this project were complex. The basement required delicate ground work. On the floors, it was necessary to meet the layout’s requirements while adapting the structure to extremely variable existing conditions, and while securing seismic brakes to existing columns. On the roof, mechanical rooms were added to house heavy equipment.

All the work required ingenuity and adaptation to preserve the architecture and thus meet heritage criteria.

Achievements of the design team

Atrium frame with very long cantilevers

Egg-shaped atrium geometry

Multiple and suspended escalator landings

Removal of several columns and installation of transfer beams

Major drilling into floors

Vast lean-to additions on the roof to house heavy equipment

New window panes of asymmetric geometry

Structure for curtain wall and canopies

Ground work in the basement

New indoor parking

Reinforcement of the existing concrete structure

Dynamic non-linear analysis of the existing building

Anti-seismic rehabilitation and installation of friction dampers.

The project was completed on a fast-track schedule between December 2000 and August 2002.

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Ramnagement de l’difice Eaton Centre-ville, Montreal

L’difice Eaton est un vaste btiment de plus de 1 million de pieds carrs rpartis sur 10 niveaux et deux sous-sols. Le btiment, dont la charpente est partiellement une ossature mtallique et partiellement une structure en bton, a t construit originalement en plusieurs tapes. Les nouvelles interventions structurales majeures devaient s’adapter aux trs nombreuses situations diffrentes qui se retrouvaient partout dans l’ensemble du btiment. Les contraintes architecturales importantes telles que la hauteur limite pour les nouveaux lments de structure, l’espacement des colonnes et la gomtrie inhabituelle, ont fait de ce projet un dfi de taille.

Sur le plan technique, d’autres dfis ont d tre relevs. On pense particulirement la ralisation de l’atrium dont la forme ovode a ncessit l’utilisation de porte–faux importants tout en tenant compte d’une part de la hauteur de plafond restreinte pour l’installation des lments structuraux et d’autre part de la capacit de levage limite de la grue tour installe sur le toit de l’difice. Le renforcement de la structure de bton, dont les dficiences n’ont t dcouvertes que lors du dbut des travaux de dmolition intrieure, a d se faire de faon minimiser le temps d’intervention et les cots. L’installation des poutres de transfert, dont certaines ont permis de couper des colonnes supportant 9 tages, reprsentait des travaux trs particuliers. Une procdure de pr-flchissement des poutres a d tre labore dans le but de prvenir une flche verticale excessive lors de la coupe des colonnes.

En fait, toutes les interventions dans ce projet taient complexes. Que ce soit au sous-sol pour de dlicats travaux de sous-uvre, sur les tages pour rpondre aux exigences architecturales de l’amnagement et pour s’adapter aux conditions existantes extrmement variables, pour l’installation des freins sismiques devant tre fixs des colonnes existantes ou au toit pour l’ajout de salles mcaniques abritant de lourds quipements. Tous les travaux ont ncessit ingniosit et adaptation afin de prserver l’architecture et ainsi rpondre aux critres patrimoniaux.

Ralisations du comit de design

Charpente d’atrium avec de trs longs porte–faux;

Gomtrie d’atrium ovode;

Paliers d’accueil d’escalateurs, multiples et suspendus;

Enlvement de plusieurs colonnes et installation de poutres de transfert;

Percements majeurs dans les planchers;

Vaste appentis au toit abritant des quipements lourds;

Nouvelle verrire gomtrie asymtrique;

Structure pour mur rideau et marquises;

Travaux de sous-uvre en sous-sol;

Nouveau stationnement intrieur;

Renforcement de la structure de bton existante;

Analyse dynamique non linaire du btiment existant;

Rhabilitation sismique et installation de freins dynamiques.

Le projet a t excut en mode “fast-track” de dcembre 2000 aot 2002.CCE

Name of project: Eaton Building Redevelopment, Montreal

Other key players: Lemay & ass. (architects), Bouthillette Parizeau & ass. (mechanical), Herve Pomerleau (construction management), Nico Metal (structural steel)