Canadian Architect

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Engineering Canadian Modernism

An excerpt from an upcoming book highlights the pivotal role played by the Yolles engineering practice in Canadian Modern architecture.

April 1, 2001
by Beth Kapusta and John McMinn

The early years of Modernism in Canada following the Second World War were characterized by a range of opportunities for technical innovation in design, construction and materials. A strong sense of optimism about the expressive power of structure fostered an integrated expression of engineering and architecture. The early 1950s also saw the evolution of engineering design methods from working stress to ultimate strength, which led to less conservative structural configurations and the ability to more easily test complex structures.

As a young engineer, Morden Yolles became interested in the work of the Swiss engineer Robert Maillart (1872-1940) through his reading of Sigfried Giedion’s Space, Time and Architecture. In Maillart’s milieu, the cost of labour was low compared with the cost of materials, leading him to create concrete structures that minimized material by reducing elements not required for structural performance. His use of an innovative two-way flat slab produced columns that merged seamlessly with the slab, the result of a holistic understanding of structure in which all parts act together rather than as a collection of independently functioning components. For Yolles, Maillart’s graceful arched slab bridges epitomized the philosophy that would dominate his firm for the next five decades: the search for elegant economy, employing the most advanced technology of the time, grounded in a comprehensive understanding of the underlying principles of structural behaviour.

Yolles was also influenced by the work of the Italian architect and engineer Pier Luigi Nervi (1891-1979). One of Nervi’s great accomplishments was the use of hyperbolic paraboloid structural forms to deal with variable sectional requirements. For Yolles, the inseparability of art and function in Nervi’s work was inspirational.

However, these European precedents were antithetical to the post-war construction climate in Canada, where the industry faced increasing labour costs. Engineers had to develop structural systems that reduced labour even at the expense of increased material content. Under these conditions, Morden Yolles’ passion for expressive and labour-intensive structural form was often at odds with a strongly felt conscience about structural economy.

Nevertheless, significant technical and architectural innovation characterized the work of the firm, especially where a desire for expression combined with a good collaborative climate between architect, client and engineer. The 1950s and 1960s saw the consistent development of the visual expression of structure, greatly facilitated by the extraordinary abilities in analysis and design of complex structures which Roly Bergmann brought when he joined the firm in 1955. Yolles was known for his ability to distill simple principles from complex circumstances, and his commitment to economical expression made him a favourite early collaborator. Bergmann contributed his knack for working out complex geometrical configurations, his keen problem-solving intuition and his legendary sketches that bridged the communication gap between architects and engineers.

Collaborations: Peter Dickinson

Modernism had been something of an abstract love for Morden Yolles in his early career, so the opportunity to work with Peter Dickinson, fresh from England and trained at the renowned Architectural Association in what was being called the “New Architecture,” was welcome and exciting. The Benvenuto (1951), a luxury apartment-hotel designed by Dickinson when he was with the firm of Page and Steele, stands as one of the earliest and finest examples of the International Style in Toronto. Its sleek horizontal lines and elegant strip windows provided unprecedented transparency and spectacular views of the downtown core. This effect was achieved using a new method of structural analysis for an elastically designed flat plate slab, which accentuated the clean horizontality by eliminating column capitals and drops–bulky stiffening elements where columns meet the slab. The structure was the first of its kind in Toronto.

The Benvenuto is an early example of the use of the iterative method of analysis to determine bending moment distribution in a structure, an evolution from the approximate methods of analysis previously used for indeterminate structures. Special approval was required from the Toronto Building Department, as existing local codes did not permit this form of analysis, although the American Concrete Institute in the United States had accepted it.

Another of Dickinson’s projects with Page and Steele, the Queen Elizabeth Building at the Canadian National Exhibition (1955; originally called the Women’s Building), is an early example of folded plate technology applied to create long-span bays. The original design called for an unbraced suspended arch structure consisting of 50-foot arches supporting a suspended flat roof. The design proved too expensive, so Yolles, inspired by new industrial buildings published in contemporary European journals, proposed the folded plate structure. Thin five-inch slabs provided material economy while creating the striking expressive character sought by Dickinson as a radical contrast to the surrounding neo-classical exhibition buildings. Having proposed the solution, Yolles had to find someone with the technical expertise to execute the design of this complex structure. A colleague recommended Roly Bergmann, who was working at the time for the firm of Lazarides, Lount & Partners.

The engineering solution solves, from first principles, several of the inherent design challenges of folded plate design, including the tendency of the structure to flatten where each peak of the folded surface wants to drop. Cumulatively, therefore, the entire roof structure creates a substantial outward thrust, causing the supporting piers to kick outward. This is countered by a system of post-tensioned steel ties in the foundation, transferring the roof thrust through a series of shear walls at either end of the building. By understanding and analyzing the building as a whole rather than a series of individual bays, the engineers were able to devise an expressive solution to the design of a long-span building, one which embodies an idealism appropriate to a national exhibition.

Ron Thom

Selected to co-ordinate the master plan and design the first phase of Trent University on the outskirts of Peterborough, Ontario, Ron Thom proposed a romantic architectural plan based on the Oxbridge collegiate tradition. The original master plan featured buildings on either side of the Otonabee River linked by pedestrian bridges.

Since buildings at Trent would be designed by different architects over a period of years, Thom sought to maintain visual coherence by enshrining reinforced concrete and timber as the primary materials of the campus. Concrete is used in a variety of ways, including the first and very rare example of rubble aggregate concrete in Canada. Inspired by Eero Saarinen’s Ezra Stiles and Morse Colleges at Yale University, Thom used rubble aggregate concrete as both structure and surface for Champlain College and the Bata Library.

Asked at an early presentation if the proposed rubble aggregate concrete would last 100 years, both Ron Thom and Morden Yolles assured the university that it would. More than three decades later, these walls constitute the material signature of a unified institutional expression widely recognized as one of the most notable university projects in Canada, and stand as a reminder of the intensive and trusting collaboration between the Yolles firm and Ron Thom.

Once construction finally began, the process was labour-intensive. Rubble aggregate consists of monolithic reinforced concrete walls incorporating irregular football-sized stones exposed in the wall surface. Galvanized steel tubes two inches in diameter were inserted at regular intervals in the middle of the form-work prior to dumping in the stone. The tubes were used to pump in the grout progressively from the base of the forms upward, ensuring that no air pockets formed. Finally, on
ce the grout was sufficiently dry, the forms were stripped and the concrete manually scraped back to expose the rough rock faces. A process that began with state-of-the-art techniques in concrete construction was completed with crews of masons hand- finishing the exposed concrete surfaces.

Thom decided very early in the design process that the Reginald Faryon pedestrian bridge, conceived as a focal element linking the campus on either side of the river, would also be constructed of concrete to reflect the character of the buildings. Drawing on their influences, Yolles and partner Roly Bergmann’s first proposal was an arch based on designs by Maillart. Thom felt it looked too much like a highway bridge, so Yolles proposed the more Nervian idea of introducing warped planes. The final bridge form is essentially a three-hinged arch with a centre span of 192 feet, a 22-foot approach span at the west and a 76-foot cranked beam approach span from the east. The arched ribs of the centre span and the cranked beams of the eastern approach span have post-tensioned profiles.

After Trent University, Yolles again worked with Thom when the architect was selected to prepare the master plan and design major buildings at the Metro Toronto Zoo in 1970. The zoo represents one of the last heroic, large-scale projects of post-war Canadian Modern architecture. Thom served as head designer, in joint venture with Clifford & Lawrie Architects.

The most notable buildings in the Zoo complex are the African and Indo-Malayan pavilions. They are constructed as a series of irregularly faceted hyperbolic paraboloid roof planes covering a similarly irregular topography. At the outset, Ron Thom had wanted to avoid making what he called a “prison for animals,” aiming for spaces as non-building-like as possible, in a “continuous environment of humans, flora and fauna.”

The geometry of the plan suggested by the prominent engineer Douglas Wright and worked out by Roly Bergmann is brilliantly simple, yet appears as a complex abstracted landscape as varied as the natural landforms that surround it. During development of the project, Yolles contacted Wright, who had been working with hyperbolic paraboloid structures and developing the Triodetic system of aluminum tubes and joints. Each building is an assembly of two modules, 42-foot squares and rhomboids, with 90-degree, 60-degree and 30-degree corners. An infinite variety in surface topography is made possible simply by varying the apex and base of each section of the roof surface, creating what appears to be an extremely complex building.

The structure is supported on cast-in-place concrete tripods from which hollow-section steel beams extend at various angles to the peak of each roof area. Between the main steel members, the hyperbolic paraboloid surfaces are formed by a Triodetic grid system of aluminum tubes and nodes, formed of either equal-sided squares or pentagons, intersected with diagonals which carry the roof load in pure tension. This allowed members to be relatively small and light, helping to keep the overall roof sections as thin as possible. The Triodetic structure is topped by 2″x 6″ cedar joists and tongue-and-groove cedar decking. The original cedar shingle roof surface was recently replaced with copper sheathing.

Raymond Moriyama

Yolles’ collaborations with architect Raymond Moriyama of Moriyama & Teshima Architects began during the 1960s with the Japanese Canadian Cultural Centre, a bold and highly articulated essay in the use of pre-cast concrete and cast-in-place structural framing members combined with pre-cast cladding elements. The building elegantly combines a Brutalist structural composition with finely textured relief panels, exploring the expressive potential of concrete, while exhibiting a distinctly Japanese sensibility. The assertive character of the structure was intended by the architect to symbolize the Japanese-Canadian community’s process of re-establishing its place in society after the trauma of internment during the Second World War.

Soon after the completion of the Cultural Centre, Moriyama collaborated with Yolles on a much larger building complex for the Ontario Science Centre, begun in 1965, a project typical of the many large government-funded cultural commissions of the period.

From an engineering point of view, its most interesting feature is the pedestrian bridge linking the entrance building with the triangular core building. The architect wanted the bridge entirely glazed on the north side, with unencumbered views of the ravine it traversed, and solid on the south, providing display space along its 210-foot length. The daring solution of a folded plate concrete bridge, held by four massive claws supported on tapered piers, establishes the upper floor of the two-level walkway and encloses a space below carrying mechanical and electrical services running from the entrance building to the remainder of the complex. The blank south wall of the bridge extends to a height of 30 feet and is enclosed by a metal deck on steel beams, supported on the north side by concrete columns. The supporting claws were post-tensioned to resist the large overturning forces involved. As a result of the asymmetrical bridge section, post-tensioned tie-down cables linked to the concrete supporting piers were also used to prevent the bridge from overturning.

The exuberant gestures and relentless use of concrete on both the interior and exterior of the Science Centre may now seem heavy-handed, and the exterior surfaces are marred by the inevitable problems of staining. Yet the vast scale and boldness of the Centre mark it as an expression of the confidence and optimism of the period in which it was built. Like many other projects of the time–such as John Andrews’ Scarborough College and Arthur Erickson’s Simon Fraser University–the Science Centre is interesting more for siting strategy, responding to and creating a powerful experience of its natural setting at the scale of landscape, than for its somewhat crude formal gestures. In an article on the heroic era of Canadian architecture, English critic Peter Buchanan invoked an attitude that could describe the Science Centre: “Architecture need no longer be overwhelmed by nature but can be its equal in a new harmony… Verging on triumphalism in announcing this equality… they project some powerful transcendent myth of Canada unified by the grandeur of the land to which human settlement could at least be an adequate partner” (see CA March 1994).

These great collaborations mark one of the most prolific periods of architecture and engineering work in the history of the country. But they also foreshadowed, in their often overwhelming scale and heroic intentions, the subsequent loss of faith which would ultimately lead to a reaction against the Modern movement in Canada. Nevertheless, their legacy, which combines an honesty of expression with the collaborative efforts of their architects and engineers, remains one of the most interesting and fruitful periods of Canadian Modern architecture.

Beth Kapusta and John McMinn are preparing a book on the Yolles engineering practice, due to be published in February 2002.




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