Canadian Consulting Engineer

STRUCTURES: The Yolles Legacy

December 1, 2002
By Canadian Consulting Engineer

At the crowded launch of Yolles: A Canadian Engineering Legacy in October, most of the people were young architects. They had come to pay homage to a firm of structural engineers for whom they have th...

At the crowded launch of Yolles: A Canadian Engineering Legacy in October, most of the people were young architects. They had come to pay homage to a firm of structural engineers for whom they have the deepest respect.

Yolles Partnership’s close collaboration with architects is legend. For half a century the Toronto firm has been at the centre of things, helping to realize some of Canada’s most admired buildings, as well as international landmarks such as Canary Wharf and Battery Park. As authors Beth Kapusta and John McMinn suggest in the preface to this polished and beautifully executed book, a survey of Yolles’s work amounts to a cross section through architecture and construction in the last 50 years.

The late Roland Bergmann, an “engineer’s engineer” who came from Austria, joined Morden Yolles, a native of Toronto, in the 1950s. Together, this unusual pair set out on a road that would take their company through the thriving 1960s and 1970s, suffer during the construction industry collapse of the early 1990s, then regenerate again under the leadership of Andy Bergmann, P.Eng., Roland’s son.

The following extract describes Yolles’s early work in the 1950s, when engineers and architects were making strides in the exciting and expressive forms of modernism..

From Yolles: A Canadian Engineering Legacy. By Beth Kapusta and John McMinn. Douglas & McIntyre, Vancouver, 2002

Charting Canadian Modernism

For an engineering firm like Yolles emerging in the 1950s, the early years of modernism in Canada were characterized by opportunities for technical innovation in design, construction, and the use of materials. A strong sense of optimism about the expressive power of structure led to more buildings that integrated architectural and engineering expression and, in turn, to freer organization of space within buildings. Likewise, the industrialization of building construction accelerated in this period, with bold experiments in structural form taking place on an unprecedented level, most notably in reinforced concrete design. The 1950s and early 1960s also saw engineering design evolve. The use of ultimate strength design in reinforced concrete gave structural designers a greater sense of freedom and the ability to more easily test increasingly complex structures.

Through his reading of Sigfried Giedion’s Space, Time and Architecture, [Morden] Yolles had become interested in the work of the Swiss engineer Robert Maillart (1872-1940). Before the Second World War, labour costs were very low relative to material costs, leading Maillart to create concrete structures that minimized material by reducing any elements not necessary to structural performance. Maillart’s innovative two-way flat slab produced a column that merged seamlessly with the slab, developed through a holistic approach to structure in which all parts act together, rather than as a collection of independently functioning elements. . . .

Morden Yolles’s work was also influenced by the work of the Italian architect and engineer Pier Luigi Nervi (1891-1979), whose use of the reinforced concrete rigid frame was both economical and beautiful. For Morden Yolles, the inseparability of art and function in Nervi’s works was inspirational.

Innovations in Collaborative Design

These European precedents left Yolles with something of a dilemma in 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 quantities of material. Under these conditions, Morden Yolles’s passion for expressive structural form, which was often labour intensive, was at odds with the prevailing engineering ethic that stressed labour economy.

Nevertheless, the firm fostered significant technical and architectural innovations, especially where a desire for expression and a good collaborative climate existed between architect, client, and engineer. The 1950s and 1960s saw the visual expression of structure consistently develop, greatly facilitated by extraordinary abilities in the analysis and design of complex structures, which Roly Bergmann brought with him when he joined the firm in 1955.

Shell-form concrete structures, an area of expertise for Bergmann with his exceptional intuition and computational abilities, provided another direction that broke the expressively limited mould of pre-war construction. Like other leading structural designers, Yolles engineers saw tremendous potential in exploring complex geometrical forms in which architectural and structural expression were integrated. They found inspiration in the work of the Spanish-born architect Flix Candela, particularly his shell-form structures made both in concrete and with reticulated grid-like steel frames. Yet the economics of construction in more industrialized countries differed dramatically from those in Mexico where Candela practiced, particularly with respect to labour costs. As a result, thin-shell concrete construction was never applied in Canada in more than a few idiosyncratic projects, such as the Cleeve Horne House (1956) in Pickering Township, northeast of Toronto, which was the result of a small competition sponsored by the noted portrait painter and his wife, Jean, a sculptor.

Working closely with architects Clifford & Lawrie, Yolles came up with a radically simple winning solution: a thin-shell concrete hypar. The scheme was at first rejected, assuming excessive cost, but after considering the alternatives, it was adopted and built for a little over CDN $12 per square foot, at a reasonable budget for that time of CDN $22,000. The 42- by 42-foot, 2-inch-thick concrete roof is supported at two corners by concrete buttresses. . . . Still virtually unaltered since its construction, the home, which has been listed by the local historical board, is furnished throughout with vintage 1950s modernist furniture.

Even though this pioneering Canadian work on hyperbolic paraboloid shells led only to isolated applications, the post-war optimism and exuberant confidence embodied in the Cleeve Horne House later found expression on a grand scale at Expo 67. The buildings produced for this remarkable world’s fair in Montreal marked the most concentrated collection of modernist building experiments ever undertaken in Canada, with many countries contributing an extraordinary variety of daring, expressive designs. The United States built the aforementioned 20-storey geodesic sphere by Buckminster Fuller; West Germany’s Frei Otto designed a tent-like roof of steel mesh, covered by a polymer fabric, suspended from giant masts; the British cantilevered their exhibitions over a yawning moat; the Russians hung huge sheets of glass from a ski-jump shaped concrete roof.

Canada’s contribution to what Time called “a skyline of amazing shapes” was the Canadian Government pavilion, a massive inverted pyramid named Katimavik, “gathering place” in the Inuktitut language of Canada’s northern indigenous population. The inverted pyramid (designed by an architectural team consisting of Z. Matthew Stankiewicz and Robbie, Vaughan & Williams), and engineered by Yolles’s Roly Bergmann, was formed by a structural steel space grid. Architect Rod Robbie recalled a moment of heart-stopping tension as the scaffold towers were lowered to release the corners of the top of the structure. Bergmann watched through a theodolite, telling the architect that the corners were still dropping. For a few tense moments all had nightmare images of the structure slowly turning inside out as the towers came down. However, the structure finally settled exactly as it was meant to, creating an optical illusion of a level upper rim and straight sloping sides, an effect achieved through a subtly curved structure devised by Bergmann.


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