TEHRAN–An ancient arch bridge dating back to roughly 1,700 years ago in Dezful, southwestern Khuzestan province, has undergone some rehabilitation works, the provincial tourism chief has said.

A budget of 24 billion rials ($80,000) has been allocated to the project, Mohammad Hossein Arastuzadeh said on Monday.

The restoration of the bridge, which is one of the top tourist attractions of the region, is being carried out under the supervision of experienced restorers and cultural heritage experts, the official added.

Best known as the Dezful bridge, the massive monument on the Dez River is believed to be the oldest still-standing bridge in the world and it remained in full functionality until recently.

The Sassanid-era structure has been extensively repaired and renovated in various eras to ensure its functionality and preservation. Nowadays, cars are no longer allowed to pass over the structure due to its historical value and fragility.

It is said that the monument was built by Roman prisoners of war after suffering a defeat at the hands of the Sassanid king Shapur I the Great, who reigned over Persia from around 240-270 CE.

An arch bridge carries loads primarily by compression, which experts on the foundation both vertical and horizontal forces. Arch foundations must therefore prevent both vertical settling and horizontal sliding. Despite the more complicated foundation design, the structure itself normally requires less material than a beam bridge of the same span.

Arch bridges can be classified into deck arch bridges (featuring arches below the deck) and through arch bridges (those with arches above the deck, generally tied arches). In all arch bridges, structural difficulty can be found in the minimization of the misalignment of the arch axis and the line of thrust, as well as sufficient bending and buckling resistance. General design recommendations focus principally on the arch-to-span ratio, the arch and deck slenderness, and the number of hangers or piers.

Recent innovative arch bridges include high-speed railway (HSR) bridges, concrete-filled steel tubular and precast concrete arches, high-performance concrete or ultra-high performance concrete arches, and steel-concrete composite arches, and feature innovative erection methods.

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