Identifying the Factors that Promote Conceptual Design
Despite the variety of structures examined here, they all demonstrate a common trait—their relative success or failure was largely determined during the conceptual design stage, when the engineer made the initial decisions about materiality, structural form, placement, and visual impact.
For example, Menn drew from the work of his predecessors, particularly Robert Maillart, and eventually transformed their ideas to take advantage of the qualities of a new material, prestressed concrete. Prestressed concrete brought the potential for more dramatic forms, but at the expense of more complex structural systems. As we saw with the Felsenau and Sunniberg Bridges, however, Menn responded with a conceptual process that carefully considered the structural and social implications of this new complexity and scale.
During the conceptual design stage, Schlaich depends heavily on sketches, models, and very simple structural formulas to carry his work from the initial idea to a relatively complete design before moving to more complex analyses to refine his design. Further, by taking the time during the conceptual design stage to develop a thorough understanding of the project criteria, the forms he creates have a natural relationship to their social, scientific, and cultural context.
On the other hand, for the design of the Alamillo Bridge, Calatrava pushed his design process beyond the boundaries of the engineering discipline to pure sculptural expression. The resulting concept, unbounded by requirements of efficiency and economy, is arguably better judged as art than as engineering.
Additionally, however, within these examples one sees evidence that the success of the structure is not dependent solely on the engineer’s work. In many cases, a strong supporting network of social, economic, political, and professional factors has helped to drive the creative process by generating an environment that encourages a creative and innovative approach, not just an economical one. Having examined the case studies, one can summarize some factors that seem to promote strong conceptual design.
The Vision of the Designer
The engineer must recognize that he has the opportunity and the responsibility to consider the structure in relation to its effect on society. This requires a perspective that extends beyond the issue of analysis to much broader and potentially influential ideas about economy, efficiency, and elegance.
The Understanding of Structural Design as an Evolutionary Process
The conceptual design process requires strong familiarity with precedent and the understanding that the engineer is working as part of a tradition that can be built upon and improved. Although a seemingly contradictory idea, the more successful engineers achieve innovation and variety through repetition and the steady transformation of established ideas.
Simple Analysis Methods
The bridges examined here demonstrate that simple analysis methods can lead to a thorough vision of the structure and a more intuitive understanding of its behavior. Complex mathematical and computer analysis can certainly have a beneficial role in structural design, however as a tool for checking and refining a design at the later stages rather than as a generator of form.
In several of the bridges I studied, the design arose from a design competition. The success of the design competition in promoting strong and innovative designs can be attributed in part to several key issues. Specifically, competitions:
- are founded on the idea that there is more than one solution to each problem and that economy, efficiency, and elegance are not mutually exclusive criteria. In fact, as we have seen, the interaction of the three can lead to a more complex and rich design.
- encourage solutions that respond to a variety of social and scientific constraints.
- generate intellectual discussion within the profession.
- allow public interaction and feedback, which helps to give form to the structure in a way that responds to the desires of the community.
Writing about Conceptual Design
Menn, Calatrava, Schlaich, and others have contributed to the body of writing on conceptual design and have documented the specific design processes they followed. The act of documenting their methods has helped to make their ideas more accessible to the profession and to generate a constructive dialogue about the role of conceptual design in engineering.
Above all, the engineers who create remarkable structures recognize that structural design is an active process. Innovation and originality do not simply emerge out of equations and purely rational ideas. Rather these engineers have manipulated form to best fulfill the various social, symbolic, and scientific criteria—factors that may or may not be rational. Elegant designs are created by the hands of the engineer-artist who develops the skills to balance this complex array of influences.