01 November 2020

"Bridging: by Foot and Bicycle" by Ney & Partners

Here is an excellent book devoted to  the designers du jour in the world of bridges, Ney and Partners. Once past its ungrammatical title, Bridging. By Foot and Bicycle (Archibooks, 264pp, 2019) is an excellent and very well-presented survey of the firm's pedestrian bridge oeuvre, filled with photos, visualisations, drawings, diagrams and informative text (in both French and English). As with the firm's bridges, the book is not completely without its flaws, but I can recommend it to anyone with a serious interest in the very best bridge design.

An introduction titled "A bridge has to be designed!" by Laurent Ney sets the tone. Ney reports his experience working on a project with a large multi-disciplinary firm, who apparently responded with embarrassed silence when Ney asked "Who designed the bridge?" While this hardly rings true (such firms are obviously well populated with people who design bridges) his point is that the norm in design firms when presented with a bridge project is not to design from a tabula rasa, but to select and adapt from an existing structural typology. His argument is that there is no real "design" in this approach.

This is the very opposite of Ney's own modus operandi which is (to at least some extent), to see how context and constraints can point the way to creative opportunities, minimising preconceptions wherever possible. This book illustrates that effectively, explaining in detail the design decisions that were made on the various projects featured.

From the outset, this also highlights a lacuna that recurs throughout the book. It is the designer's perspective, and largely a history of various designed objects and why they are how they are. There is little in the way of self-criticism, and essentially no space for the voice of those who commission or use these bridges. This is not uncommon in an architectural monograph, and in this case, where much of the discussion is inevitably somewhat technical, the sense that there are people on the bridges and they may have something to tell us sometimes vanishes entirely.

The technical element in the book is inevitable given the superlative engineering at the core of many of Ney and Partners' bridges. Sometimes, their astonishing bridges seem to be the output of a designer who is operating as a naïf, ignorant of the conventions of bridge design and hence able to devise solutions that would never even enter the peripheral vision of an experienced engineer. At other times, they seem the work of an auteur, someone with an in-depth understanding of the bridge engineering craft but the desire to pursue excellence and never accept compromise.

Fellow engineers often admire Ney and Partners' bridges because this approach - creative, challenging, courageous - leads to structures which are remarkable in their geometric perfection and economy of detail, slimmed down well beyond what others ever attempt, let alone achieve. This is why the technical issues are key throughout the book and it could never be purely about the architectural aspects of design.

Although the bridge designs featured often take the idea of refinement to extremes, the bridges are only rarely completely rational in their conception. It's always clear that intuition has been applied, and subjective choices made. This is particularly the case in the first few bridges presented, which share a theme of history and context.

The as-yet unbuilt Poissy Footbridge is a proposal for a new bridge on the site of the remnants of a historic bridge across the River Seine. The historic Pont de Poissy was largely destroyed in 1944, and never rebuilt. The Ney design follows the same alignment but flies above the remaining bridge piers, supported from tetradactyl steel supports sitting in between the original masonry. The new bridge's longest span is 93m, yet the deck is formed from a single, ultra-slender folded steel plate. The impression is of a gently undulating ribbon, dancing across the river, dipping down over the existing piers but darting back away from them as if suspended on air. It is both a little incongruous, giving the initial impression of being structurally unreasonable, and also rather stunning.

Dejima Footbridge, completed in 2017 in Nagasaki is very different but illustrates some of the same aspects of the Ney philosophy. This is a cantilever bridge, arranged with one fixed end so that the "free" end imposes as little load as possible on the more archaeologically sensitive of the two river banks. The two edge girders feature multiple rows of stiffening plates, with the web perforated in a visually interesting manner. However, the stiffeners are to a great extent decorative, and the shape of the girders gives the visual impression that the bridge functions like an arch. It's a beautiful structure, but the engineering and architecture are not integrated in the way that many other Ney designs achieve.

The book's discussion of the Tintagel Footbridge serves to illustrate the point that Ney and Partners don't entirely ignore conventional typologies, but that their design process can allow them to take or adapt those standard forms in interesting and site-appropriate ways. At this site, Ney's analysis of the normal bridge forms led them towards an arch as a visually and contextually desirable proposal for the site.

A key issue at Tintagel was the difficult access for construction, leading to consideration of a bridge which was built by cantilevering from its supports (a well-trodden method for building metal arch bridges). The bridge as-built retains the cantilever form, as making it into a genuine arch would have been structurally far more challenging (a result of the sag curve of the pathway, and the consequences for thermal restraint).

It's a spectacular bridge and the engineering and architectural ideas are well-explained in this book, but very little is said about how its users find it (especially with such filigree parapets high above a chasm, and with a gap in the floor at midspan).

The same is true of a structure like the Park Footbridge in Antwerp. This is one of a number of designs where Ney and Partners apply a "subtractive process", defining a stable shape and form, generally in thin sheet metal, and then looking to see what metal is unnecessary and can be cut away (the carbon balance of reduced material versus increased fabrication process is never discussed). The structure here is a hybrid between a bowstring arch and a box girder, although, as with many architects, that's a term that's never used - after all, who would celebrate being able to walk through the interior of a girder (it's not 1850 any more)?

It's an amazing work of structural engineering, absent all the bolts and stiffeners that a normal box girder interior displays. The webs are perforated in a manner that takes account of levels of stress, but is not entirely determined by that, with far more material left in place than can be structurally necessary - compare a proper bowstring arch where a handful of cables suffice to connect the arch to the bridge deck. It looks like an amazing experience to walk through but ... why is it a covered bridge at all? Will the patterns of illumination inside be tolerated by pedestrians susceptible to flicker? And is a floor-rail, an obvious trip-hazard, really the best way to stop cyclists bashing their heads on the girder web? To me, it feels like the uncompromising desire to maintain the purity of the design object results in a design that is not completely comfortable.

This is not the only Ney bridge where this can be said. The Vluchthaven Footbridge in Amsterdam has the same sinuous deck plate as the Poissy design, and an ingenious parapet design. The client was keen to address the common Amsterdam problem where bridge parapets serve as a favoured place for bicycles to be parked and locked. Ney and Partners came up with an elegant parapet design with all verticals - no top rail or handrail. If someone were foolish enough to lock a bicycle here, it could just be lifted off. It's smart and very well detailed - but handrails are a good thing for many bridge users, especially the elderly or infirm who may want to take the opportunity to stop and briefly secure a handhold. This does not appear to a bridge for stopping on.

A very different result from the subtractive approach mentioned above is the Knokke Footbridge, which I discussed right back in 2009. This is, in my view, one of the firm's masterpieces, using one curved steel plate to satisfy the requirements both of transverse load distribution (a curved skin acting in tension) and as the primary longitudinal structure (sharing the characteristics of a suspension bridge and also of a Robert Maillart arch, inverted). The Y-shaped bridge supports, and the way they hold up the deck, are brilliant.

In writing this book review I've been drawn to writing about the flaws in these designs, because I feel that the monograph style of the book (uncritical, celebratory) and the presentation entirely from the designer's perspective (their subjective view is privileged over anything else) do beg for some degree of challenge.

However, Ney and Partners are easily one of the best bridge designers working today, bringing together a very rare blend of imagination with the superlative technical ability required to turn their audaciousness into reality. They operate way beyond the level of the vast majority of bridge designers.

The breadth and variety of their designs shows that they do take context seriously (contrast their designs, for example, with someone like Calatrava). The detailing of their bridges is frequently exquisite, and the book's photographs and technical drawings make that abundantly clear. I can't imagine a bridge designer who wouldn't enjoy and learn from this book, and non-specialists should also find their work well worth discovering in more detail.