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Measure - Aoibheann Ní Mhearáin

With the Traversina bridge, the very inaccessibilty of the site became the exact measure of the bridge. Situated along the ancient Roman Viamala trail in Switzerland, all materials had to be flown on site and so the weight of the bridge's truss was limited by a helicopter's capacity to carry it. Conzett chose to see this limitations as a source however, and produced a strikingly beautiful and thoroughly rigorous piece of engineering. The bridge is composed of a lightweight truss substructure which is first fixed to the abutments, and is subsequently stabilised by the heavy superstructure of the walkway. This method of combining two different structures dates from the Baroque period. The duality here is potent.

His second bridge along the Viamala trail, the Suransuns bridge, also joins two different traditions. To the north the tradition is of timber construction while to the south, stone is the predominant material for construction. Conzett looked initially at combining the two materials but instead produced, what is effectively, a rope bridge in stone. The stone steps of the stress-ribbon bridge echo the winding pathways of the Viamala trail. The 60mm thick steps of pre-stressed granite were strung on stainless steel ribbons, these were subsequently post-tensioned so that the slabs were wedged together to form an inversely arched bridge. Stone is a heavy material and not an obvious choice for a suspended bridge. It is the very weight of the stone, conversely, that makes the bridge work, its heaviness limits deformation and provides stability. A balance is struck.

The work presented - as well as the lecture itself - was delivered with consummate care. Yet Conzett was clear to point out the influence of the arbitrary, the unanticipated component that calculations alone don't have tolerances for. What is necessary is a dialogue, an interaction, an outside influence. If we look carefully, we can choose the right weights to measure.

Aoibheann Ní Mhearáin is an architect currently working with Grafton Architects.