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The paper describes the network arches built at the grade separated junction of the II/468 road and the industrial area of Trinec-Baliny in the Czech Republic. A network arch is defined as an arch bridge with inclined hangers where some hangers cross other hangers at least twice. The tie is formed by a concrete slab with longitudinal prestress. Owing to the arrangement of hangers, there is little bending in the tie and the arches. All hangers have the same cross-section. Their connections should be placed equidistantly along the arch; the hangers act like a light web. The two 73·5 m span network arch bridges described in the paper and the adjacent approach ramps work as one articulation system. The paper presents the prestressing arrangement of the prestressed concrete deck, the unique bridge articulation without fixed bearing and the prestressing of the interchange between the arch bridges (the part where the approach ramps turn left and right from the longitudinal axis of the bridges). The activation of the bridge hangers is also described, together with the results of the long-term monitoring (the bridges were put in operation in April 2009).

The arch is the oldest structural shape that mankind has invented. The Romans constructed a large number of stone arch bridges on roads or water supply routes (aqueducts), many of which have survived to the present day. Arch bridges were constructed throughout medieval times; some of them represent masterpieces of the world´s cultural heritage. Buried concrete arch bridges are built with spans from 2 m up to 40 m on roads and railways, both as underbridges or overbridges, and as pre-cast and cast-in-place structures. Owing to low construction costs, great durability and endurance, they are favoured by contractors and owners. This paper focuses on the structure–soil interaction of buried arch bridges both in operation and under construction. Based on analytical derivation, a method of centre-line optimisation of cast-in-place buried concrete arch bridges is proposed and applied on an existing structure. The method leads to reduction of bending moments and deflections, thus making the structural system more effective. The impact of the construction phases on the distribution of internal forces is studied. Based on the acquired knowledge, modifications of the construction process are proposed and evaluated.