Professor Vitek, PhD, CEng, an expert in concrete structures and a visiting professor at the Czech Technical University gave a talk on 22 September 2010 about the construction of the Oparno bridge, a reinforced concrete arch carrying a four lane motorway from Prague to Dresden.  

 

The bridge crosses a valley in a scenic hilly landscape nature reserve in the Ceske Stredohori Mountains.  It consists of two almost identical independent parallel arches, each with a span of 135 metres.  The length of the bridge is in order of 275 metres and is the second longest concrete arch span of the in the Czech Republic. 

Due to the location, special requirements and limitations had to be met. 

No access was allowed to the valley during construction so each arch was built using a cantilever casting method with temporary stays and pylons, which called for the careful control and monitoring of deflections. A form traveller technology was used to cast the arch segments, each around 5 m long.  The individual segments were temporarily supported by stays anchored in piers and in temporary pylons. The bridge deck was cast using an overhead movable scaffolding system. 

Each reinforced concrete arch has a variable thickness of 1.3 to 2.4 metres and a width of 7 metres.
The cross-section is composed of the two longitudinal ribs connected by a thin upper slab.
Each longitudinally prestressed bridge deck has two beams 1.2 metres deep and is 14.3 metres wide. 

The bridge was constructed from high strength concrete, which resulted in significant savings in materials and energy. Special attention was paid to the concrete mix design, quality and surface control to avoid concrete cracking and to ensure durability and an aesthetic appearance. The large elements of the bridge that were sensitive to the development of high heat of hydration were cooled by a piped system of iced water to keep temperature gradients within acceptable limits.