TEHRAN—The restoration process for Khatun Bridge, an ancient arched monument in Karaj, may take two years to be completed, Alborz province’s tourism chief said on Thursday.

“The restoration operation is estimated to take two years… However, the operation will not stop even in winter, and in case of rain, the bridge will be sheltered,” Freydun Mohammadi said.

“The restoration cost is estimated to hit four billion rials (about $133,000),” the official said.

The deck of the monument partially collapsed in December 2020, reportedly due to severe rainfalls.

Experts say the foundation of the bridge was constructed during the Seljuk era (1037–1194) while its other sections were thoroughly renovated in the time of Safavids (1501–1736).

Arch bridges have been built since ancient times due to the easy accessibility of stone masonry, which is an appropriate material for sustaining compressive forces. 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.

AM