Iceland bridges: 6. Hvítá bridge

This is the last bridge I'm going to feature from my Iceland trip, and it's the best.

When celebrating its 90th anniversary in 2002, the Association of Chartered Engineers in Iceland designated this bridge the most notable achievement of the third decade of the 20th century, the only bridge to make their list.

The bridge was built in 1928 by the national highway authority to a design by their engineer Árni Pálsson - it was one of the first projects in his career there, he went on to become their chief engineer in 1947.

The structure is 106m long, with two 51m span concrete arches spanning the river Hvítá (the "white river"). This structural form was chosen on cost grounds in preference to a two-span steel girder bridge or a one-span suspension bridge.

The structure carries the road Hvítárvallavegur between Hvítárvalla and Ferjukots. As you can see from the photo, this is a fairly rough highway, as with many in the country.

Prior to construction of the bridge, a ferry crossed the river, but this was unreliable when the river flow was high. Efforts to build a bridge began with surveys in 1910, and drawings were prepared in 1922, six years before construction eventually started.

The bridge would remain the main route from south-to-north in western Iceland until a bridge was completed downstream at Bogarnes in 1981.

The structure is instantly impressive, as attractive as many better-known concrete arches built in mainland Europe in this period. The 3m wide bridge was designed to carry a 6-tonne truck, or a uniform load of 400 kg per square metre (roughly 4 kPa), a similar load to what a pedestrian bridge would be designed for today.

The arch is very slender at its thinnest points, but unlike the broadly contemporaneous deck-stiffened arches of Robert Maillart (starting with the Flienglibach Bridge in 1923), it does not take its stiffness from the road deck.

The bridge draws its strength from the shaping of the arch - its connection to the deck at the middle of each span, and the thickening of the arch towards each support. This could have led to an ungainly appearance, but the sinuous profile of the upper arch surface combines well with the elliptical profile of the underside.

The set-back of the vertical support struts from the edges of the arch and deck also contribute to a fine appearance, emphasising the profile of the arch.

There are many more interesting bridges in Iceland, I only had time to visit a handful. Hopefully I'll get the chance to see more on a future trip!

Further information:

• Google maps
• Structurae
• Wikipedia
• Bridges of south-west and west Iceland