Tier of the Chabet IlelouÓne bridge

Lower tier of the Chabet IlelouÓne bridge. The bridge consists of three tiers: two of ashlars around a concrete core, and a third tier of concrete poured into formwork. The lowest tier is an independent bridge, 8 m high, which acts as a rigid, stable base for the two upper tiers. The two upper tiers are in fact 25 m high pillars which are cross-braced by small supporting arches that serve to inhibit sideward shift of the columns. The whole bridge is tapering upwards through a series of steps, thus reducing the weight of the upper tiers.