Astaldi S.p.A. - Euroconstruct S.A.





Orastie - Sibiu highway represents a modern road artery, important for the economic-financial implications, as for the national transportation. The project provides crossing beautiful areas, even if, to ensure traffic safety and to reduce enviromental impact, the contractor and the designer used complex but high quality technical solutions. The highwaeiy is divided in four lots: 1, Orastie - Sebes; 2; Sebes - Miercurea Sibiului; 3, Miercurea Sibiului - Saliste si Lotul 4, Saliste - Sibiu. Italrom Inginerie Internationala recved from Astaldi S.P.A., Euroconstruct Trading S.R.L., Astalrom S.R.L. JV the task of designing Lot 4 works of art. The line, on this segment, provides the execution of highway 16,235 Km beetween node of Saliste, (Km 65+965) and Sibiu belt road (Km 82+200). This highway segment presents bridges and viaducts of diverse types, an artificial gallery and many passages in areas with increased geological risk; for the km.74 segment was provided a retaining work highly important for stopping the extensive sliding phenomenon. Among the bridges placed on the segment in question, the highway viaducts placed at Km 71 and Km 73 present high interest. The first viaduct is 680 m long for 12 spans 60m each, excepting side ones - 40m long. The second, 245 m long, runs for 5 spans, 60m each (35m side ones). Both viaducts have a mixt steel-concrete deck with steel boxes and crossgirders and concrete monolith plate in longitudinal direction. The special issues for this type of structure are the absence of joints all along the bridge and the low weight of the structure because of the box shape, not affecting the sectional resistance. Pears, with variable height of 6 to 24 meters, were designed with box-section body and massive concrete head. Foundations are realised with foundations on 1200 mm diameter piles and variable lenght, not more than 30 meters. The abutments are spill-trough type, with foundations on piles. Both viaducts have separated decks for each sense of traffic. The bridges are all with precompressed girders, and have different geometry and functions. First type is represented by superior passages, conntinuos deck with 3 spans (30m central one and 12m side ones) with inner bearrings on pears posted at the highway enbankment edges and side bearrings on spill-trough abutments. Decks witdhs varies with the road importance (11m for municipal roads and 12m for regional roads). A different type was used for passages above railways for the acces straps. In this case, was chosen a solution with a single opening 21 meters long. In this situation decks width varies by the roadimportance. The structure is realised with prestressed girders systems and subsequent monolith plate, and r.c. abutments. Finally, bridges on highway, realised for low flow rivers crossings, are using single opening 21 meters long solution, on standard abutments. Deks are executed as pairs of independent decks, based on pre stressed girders unified by a monolith concrete plate. All types of bridges have foundations on piles, 1080mm diameter and 20 to 25 meters lenghts. A high interest is presented by the Km 71 segment, where the filed morphology enforced to the use of a highway tunnel, with double galleries. This work has a total lenght of 340 m, from Km 71+869 to Km 72+209m. The construction tehnology of the tunnel uses a structural section with reinforced concrete diaphragms (20m long) and monolith plates for foundation and covering. For optimising the static behaviour of the structure along the execution and minimising effects for excavations, the top-down tehnique was has been used. Also, an increased attention was accorded for the hydraulic regime in the gallery area and sizing of sewage system for water on the platform and drainage of water behind the diaphragms.