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The discussers disagree with my characterization of the inclined tower as an indirect load path. I stand by my original statements. The primary loads applied to the tower are vertical and intersect the centreline of the girder. The simplest and most effective means of resisting this load would be with a vertical member on the same line of action. Inclining the tower results in higher forces and greater reinforcement requirements. The tender drawings of the bridge show that the reinforcement. The tender drawings of the bridge show that the reinforcement in the tower is indeed considerable. In addition to conventional reinforcing steel, which would also be required in a vertical tower, we find a 25 mm thick composite exterior steel shell, 323-15 mm diameter internal post-tensioning strands, and two external stays.
The discussers claim that I have criticized the engineers, architects, and owners who have created the very innovations that I advocated elsewhere in the article. This is nonsense. The discussers do not identify a single specific innovative feature of the bridge. The article discusses technological innovations that are the outcome of a compelling need to minimize cost, and that provide new opportunities for aesthetic expression. Although it is possible that advances in bridge technology were incorporated into this bridge, the link between such advances and economy (clearly present in the Salginatobel Bridge) is not obvious, especially given the high cost of the bridge.
The discussers further state that the Esplanade Riel Bridge satisfies aesthetic criteria put forth by David P. Billington and others. I disagree. Billington writes about the aesthetics of structures within the framework of structural art, a visual art form that is distinct from architecture and sculpture, and characterized by efficiency, economy, and elegance. To Billington, the aesthetics of structures cannot be discussed without consideration of load path and cost; to him, the greatest works of structural system, low construction cost, and an aesthetically significant visual form. Given the points raised previously regarding the load path and cost of the Esplanade Riel Bridge, it is clear that this structure falls far short of the standard defined by Billington.
The discussers state that it is not valid to compare the cost of bridges intended to be “monuments” with the cost of less expensive alternatives that would satisfy the same functional requirements. I disagree. It is always valid to question the cost of public capital projects. The discussers imply that the only possible choice is between an aesthetically significant monument and a low cost structure with no aesthetic significance. This is false, as clearly demonstrated by Maillart’s bridge as well as the Menn’s Ganter Bridge, which achieved aesthetic significance through the visual expression of efficient and innovative structural systems created in response to the need to minimize cost.
The bridges of Maillart and Men were designed without any contribution from architects. Although the discussers readily agree that these are bridges of high aesthetic merit, they maintain that better bridges are produced when engineers and architects work together. It is unfortunate that they do not provide a single specific example of a bridge resulting from such a synergy in support of this statement.
As an educator, I do not share their pessimism regarding the ability of engineers to design aesthetically significant structures. There is no question that Maillart and Menn are inpiduals of immense talent. There is also no question, however, that these men benefited greatly from the guidance and inspiration offered by gifted professors. My original article discusses the need to reform the curriculum and points to Wilhelm Ritter (Maillart’s teacher) as an example to be emulated in this regard.
In their final paragraph, Messrs, Mufti, Bakht, and Tadros issue warnings against becoming “frozen in historical time” and “mired in resistance to change”. Lest there be any confusion. I re-state the final sentence of my original article, which summarizes its primary message: “ If engineers are prepared to move bridge technology forward, and if owners are willing to accept and reward innovation, then there will be a way to build, within the discipline of economy, aesthetically significant bridges with bold and original visible forms.” I stand by this statement, and remind readers that there is a difference between being frozen in history and learning from history.