Renovation to the Art Gallery of Ontario

... the facade

Frank Gehry Architect

Toronto, Ontario

Design Architect: Frank Gehry
Local Engineer: Yolles Halcrow
Steel Fabrication: Benson Steel, Mariani Metals
General Contractor: EllisDon
Cladding: Flynn

Although the main structural frame for the addition is steel, the exposed structural members used throughout the project are made from glulam timber. The large curved "arms" that will support the glass on the facade are shipped from Penticton, B.C. I have very closely followed the construction of the ROM, Leslie Dan School of Pharmacy and OCAD, and was initially surprised to see that ironworkers (Toronto Local 721) seemed to be doing the majority of the work erecting these wooden arms. (There are also members of the Carpenters Local on the job.) In fact, it makes perfect sense to have ironworkers doing the erection as they are quite experienced with handling such large members. The staging area in front of the project is extraordinarily limited, so repositioning the curved pieces as they are lifted off of the truck in order to access all 4 sides and attach the numerous galvaninzed steel plate assemblies, requires precise handling and a great deal of experience and expertise. To my knowledge we have not put up a great number of large glulam projects in the city, so to find numerous carpenters so experienced would be difficult. And of course, the connections are steel, so who better to line up the sections, ease them into place and do the bolting than ironworkers??

According to the surveyor, who I met while hanging out on Dundas Street waiting for a piece to be lifted, (and who also did surveying on Libeskind's recently completed ROM), the first arm took quite a while to position. The curves have been directly translated from Gehry's hand drawn sketches, via Catia, to the drawings, to the glulam manufacturer - then to the jobsite. Where technology permits such translation, it does not yet answer the ultimate challenge of making sure that they are properly located at a live 3D jobsite. The combined curve, rotation and slope of the elements has to be just "perfect" or the subsequent couple of dozen will not fit properly. Although the ironworkers and carpenters can perform some minor adjustments when placing the pieces, these are ultimately limited to perhaps a few shim plates - nothing major.

Translating steel erection to glulam erection also has other challenges - and requires some lateral thinking - something I have seen performed admirably by the lead ironworkers when trying to erect the ROM diagrid or Leslie Dan pods. If steel is slightly out of line, the ironworkers use "come-alongs" and "chainfalls" (mechanisms with pulleys and gearing to factor up the applied human load), to urge them into place. In the case of glulam, these mechanisms cannot be applied as they could either cause the piece to crack and fail, or damage the surface. The workers can be seen to be using the same cloth based belts and straps that are used for lifting the pieces to manually (direct one on one force), pull the pieces into position.

Working on a geometrically interesting project also translates into working without aid of the natural force of gravity to position the pieces. Mike Jackson, Toronto Ironworkers Local 721, was saying that he has to assess each piece and select the lifting point - by experience. The curved arms use two points to initially lift them off of the truck and flip them over so that they are "curve down" for final lift. The single strap is placed (by my eye) about a quarter of the way from the top. In this instance, the crane operator has limited visual access to the lift as he is located directly below and is positioning pieces over a ledge and beyond his view. He must rely on the verbal and hand signals of the lead ironworker to know how to move the piece. As per steel lifting, a rope is attached to the bottom end to lift and guide the piece into place. For the long top beam member, the steel connection makes the 7,000 pound piece substantially heavier at one end than the other. So Mike adjusted the two strap lifting points accordingly.

What might be a pleasant change for the ironworkers is the installation of the minor pieces. These can all be manually lifted and positioned.

There is also a similarity between erecting glulam and AESS (Architecturally Exposed Structural Steel). Neither can tolerate damage to its surface characteristics - so require more delicate handling and protection during placing. AESS also normally has tolerances half as great as regular structural steel - so this would prepare the ironworkers to be able to apply less force to nudge pieces into place, while connecting the steel connection pieces that are used to make the joints of glulam.

So when it comes to ironworkers and glulam, maybe ironworkers just do it better? Not sure. But it was interesting to see with the combination of glulam and steel on this job, ironworkers and carpenters working alongside and in complete unity, focusing on getting the job done, and correctly. Both fields of expertise are required.

By the way, Frank Gehry's contract with the AGO and EllisDon stipulates that no photographs are permitted to be taken of the project. I was immediately befriended by a couple of the ironworkers when they saw me hanging around (for 4 days straight) taking their photographs. Steve managed to procure me an inside tour, given by Ron, the safety guy. I had to sign a waiver that stipulated no photos (very very hard for me to follow through on!) I can only tell you that the main curved stair is going to look spectacular and that there is lots of work involved attaching the complex curved sections together. All of the shots on these pages, however, were taken from the street.

These images are for educational use only and may not be reproduced commercially without written permission. tboake@sympatico.ca