BRIDGES AND VIADUCTS

Mirna Viaduct The A9 highway (Istrian Y highway) connects the city of Pula and famous tourist centers on the west coast of Istria via the Plovanija and Kaštel border crossings with Ljubljana and Trieste, and further on with various cities of Western Europe. On the Nova Vas - Višnjan subsection of this 76.8 km long highway, the floodplain of the Mirna River is bridged by a magnificent viaduct (bridge), with a total length of 1,378 m. In addition to the Mirna River, under the viaducts there are two smaller canals and a road. The object was built on the route of the right carriageway of the highway. The viaduct for the left carriageway will be built within the scope of the completion project of the A9 highway, which will help this highway reach its full profile. Near the viaduct, the Mirna River meets the sea, and the city of Novigrad is located. The valley below the viaduct offers valuable agricultural crops. The span construction of the viaduct consists of two solid steel walls with tin carriers of constant height (2.75 m) at a distance of 5.50 m. The carriers are connected by steel cross-members and a 25 cm thick reinforced concrete pavement slab. The static system is a continuous carrier stretching over 22 spans, with a total length of 1,353.86 m. The sizes of the spans are as follows: 51.1 + 15 x 66.5 + 70.1 + 2 x 50.1 + 63.1 + 42.6 + 30.6 m. The total width of the object is 10.10 m, and it consists of two traffic lanes, each 3.5 m wide, and two protective belts, each 1.0 m wide, as well as protective fence areas, each 0.5 m wide. The ground plan of the viaduct follows a curve (R = 4,005 m). The height of its columns ranges from 13.5 to 40.0 m. Its H section is 4.5 x 3.8 (2.5) m wide and made of reinforced B35 concrete. The abutments, as well as the lower columns, are supported by a rock, while the higher columns, due to weak load-bearing soil, are based on steel 61 m long pylons, connected with reinforced concrete, and a 2.0 m thick headboard. When it comes to the quantity of materials used for the construction of the viaduct, it is as follows: B35 concrete –11,190 m3; BSt 500S reinforcing steel - 1,831 tons; structural steel of span construction St 52-3 – 2,720 tons. Investor: BINA-Istra; Designer: Zlatko Šavor, Ph.D., Master of Civil Engineering. Contractor: Bouygues France. Zvonimir Zdenko Šimunjak, Master of Civil Engineering