Canadian War Museum Structural Engineering
October 1, 2006
By Canadian Consulting Engineer
Adjeleian Allen Rubeli
Adjeleian Allen Rubeli
The Canadian War Museum is a dramatic new national cultural facility rising out of the ground at LeBreton Flats in Ottawa, within site of the Peace Tower. The museum’s purpose is to give visitors an appreciation of the destruction and suffering of war, with the message that the aftermath of war brings regeneration, hope, and peace. This theme is expressed in the design by the architects Moriyama Teshima and Griffith Rankin Cook. Adjeleian Allen Rubeli was the structural engineer.
The building structure — a combination of reinforced concrete, post-tensioned concrete and structural steel — plays a major role in expressing the architectural vision. Sloped concrete and structural steel walls, roofs and floors are exposed to view and used to provide a sense of destruction and oppression. Other areas, such as the green roof, are meant to reinforce the theme of regeneration and hope.
The numerous exposed sloped concrete walls are at angles varying from 7 to a maximum of 31 from the vertical. An engineering challenge in these structural walls was in minimizing restraint due to concrete shrinkage, creep, and thermal volumetric changes. The location of expansion joints had to be carefully selected and five major types of these joints were required.
The combination of sloped and vertical walls provides lateral horizontal load resistance for a number of different load cases. These include seismic, dead and live loads, and horizontal loads resulting from the geometry of the sloped walls and unbalanced earth pressures, particularly the 6-metre high artificial mounds of earth at the north side of the museum.
Main lobby is a wide, column-free area
The main lobby is a wide, column-free area, with sloped walls and a low ceiling, creating a feeling of compression. The lobby roof, which supports a natural grass roof covering, has a span of 27 metres. Due to the spans and loads involved in this roof, and because its structural depth had to be restricted to 2.2 metres in order to achieve the lobby’s required floor-to-ceiling height, the most effective solution was a system of post-tensioned beams and girders.
One of the key issues in the design of this roof structure was minimizing the wall restraint, which would otherwise restrain post-tensioning where the post-tensioned beams were supported on the sloped concrete walls. The solution was to provide sliding bearing pads at the jacking ends of the post-tensioned beams on the sloped walls.
Geometries in Regeneration Hall
The museum’s Regeneration Hall was created as a high, narrow and long, cathedral-like space. The structural frames consist of a unique two-hinge arch variation, leaning to the side, and with the walls and roof sloped with multiple planes.
The geometry of the hall’s steel structure is very complex. Each teetering arch frame varies and becomes progressively higher and more slender to the east. The three-dimensional geometry of the centreline of each member was created by the structural engineers using the three-dimensional geometry of the exterior skin of the building developed by the architects.
Site-cast concrete cladding
A unique feature of the museum is its exposed “site-cast concrete” cladding system. The system has all the features of a pre-cast concrete rain screen wall but with the visual appearance of cast-in-place concrete.
The $100-million building had to be designed and constructed within a tight two-year time frame. It was opened on time and on budget on May 5, 2005. Although anticipating 400,000 visitors annually, the museum saw 576,042 visitors in its first 11 months of operation.
Name of project: Canadian War Museum Structural Engineering
Award-winning Firm: Adjeleian Allen Rubeli, Ottawa – structural engineers (C. Michael Allen, P.Eng., Michael Petrescu-Comnene, P.Eng., Jon Turner, P.Eng., Kevin Weicker, Michael D’Costa, P.Eng., Garry Vopni, CET, Jean-Michel Carrire)
Architect: Moriyama Teshima Architects/Griffith Rankin Cook Architects, in joint venture
Project management: Genivar
Construction management: PCL