In 1930, Swiss civil engineer Robert Maillart completed the Salginatobel Bridge, a breathtaking 90-meter arch spanning a remote ravine in Schiers, Switzerland. At the time, concrete was primarily treated as a heavy, artificial stone suitable only for massive, solid arches patterned after classical Roman bridges. Maillart radically departed from this paradigm by viewing reinforced concrete as a light, integrated structural material.
His secret lay in the pioneering application of the hollow concrete box girder. By removing the dead structural weight from the central axis of the arch where concrete contributed minimal bending resistance, Maillart created a rigid three-hinged arch with a hollow trapezoidal cross-section. The hollow design dramatically minimized material usage, which was critical given the arduous task of transporting gravel and cement up steep Alpine roads.
Furthermore, the arch ribs, vertical cross-walls, and the bridge deck itself functioned together as a unified structural unit, sharing live vehicle loads and wind stresses efficiently. Maillart won the original design competition largely because his material-efficient concept was far cheaper than competing traditional solid proposals. Today, the Salginatobel Bridge stands as an international historic civil engineering landmark, showcasing how structural elegance and strict economic constraints can yield an enduring masterpiece of functional art.