Interesting facts about the Negrelli Viaduct:
- The important railway bridge has been in operation since 1851 and originally consisted of 85 arches.
- In 1875, a so-called connecting viaduct with additional 26 arches was connected to it.
- The viaduct, as we know it today, is made up of 15 separate structures that contain 100 arches and 5 non-arched bridge structures.
The railway bridge survived, almost unscathed, the 2002 floods, the polluted Prague air, and the ever-increasing load of railway traffic. The track that the bridge connects is 1,110 m long and goes from Karlín to Holešovice-Bubny and connects the Masaryk Station, too. In 2017, the viaduct underwent the largest and most complex reconstruction which was carried out under the auspices of the Railway Administration as the main investor.
Start of the viaduct reconstruction
The Klokner Institute has been long involved in diagnostic surveys of large bridges in Prague, so from the beginning it was also involved in assessing the state of the Negrelli Viaduct. In June 2017, we presented the methodology for the construction and technical survey. We have created a system for a detailed record of the condition of each stone masonry element before the start of repairs, and also created a basis for the design of the actual extent of the masonry repair.
How did we proceed?
From July 2017, the employees of the Klokner Institute began to carry out surveys of individual parts of the viaduct and the tests were carried out using both destructive and non-destructive methods. Since it was necessary to check every stone in the vaults, we ended up examining more than 60 thousand pieces of stone in the above-ground part of the bridge. Nineteen brick arches had to be completely taken to pieces and reassembled, using the original stones as much as possible.
Ending of the viaduct reconstruction
The imaginary end of the three-year reconstruction was the load tests. The load test examined the route from Křižíkova Street to Masaryk Station, the bridge over Křižíkova Street and the section between Křižíkova and Sokolovská Streets. In total, we tested 20 vaulted arches as well as newly built non-vaulted bridges. As a test load, we used a set of trucks, each weighing approximately 60 tons. The load test measured.
- opening of the joints in the quarters of the span and apex,
- setting of the substructure,
- wind speed,
- air temperature and supporting structures
Operations were resumed on 1 June 2020. The complexity and difficulty of the works related to the reconstruction of the Negrelli Viaduct and its extraordinary importance make this task one of the largest and most important jobs in the century-long history of the Klokner Institute.