TEHRAN – Three historical arch bridges in the northern Gilan province have undergone some rehabilitation works, the provincial tourism chief has said.

Due to their antiquity and unique architecture, the restoration of the bridges, which has been inscribed on the national heritage list, has been of utmost importance, Vali Jahani explained on Friday.

An arch bridge carries loads primarily by compression, which exerts 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. Recent research has been dedicated to the shape and magnitude of equivalent geometric imperfections, fatigue detailing, erection methods, reduction of the arch's self-weight, and new materials for arches, hangers, and ties.

Gilan is known for its tourist attractions and warm-hearted and hospitable people. The people of Gilan from different ethnic groups, including Gilak, Talesh, and Tat, have come together and formed a very rich and diverse culture and customs.

The northern region was within the sphere of influence of the successive Achaemenian, Seleucid, Parthian, and Sasanian empires that ruled Iran until the 7th century CE. The subsequent Arab conquest of Iran led to the rise of many local dynasties, and Gilan acquired an independent status that continued until 1567.

Besides, its sophisticated capital city of Rasht has long been a weekend escape for residents of Tehran who are looking to sample the famous local cuisine and hoping for some pluvial action–it's the largest and wettest town in the northern region. Gilan is divided into a coastal plain, including the large delta of Sefid Rud and adjacent parts of the Alborz range.

ABU/AM