Inspection of the landmark Polyfytos Lake Bridge of Servia
the 44 year – old and 1372 m – long bridge that connects the cities of Kozani & Larisa – Athens national road network
Introduction
The Lake Polyphytos Bridge or the Servia / Neraida High Bridge is the second longest bridge in Greece, with a length of 1,372 m designed by XEKTE SA and Prof Riccardo Morandi. Construction began in 1972 along with the artificial lake and was completed in 1975. The bridge has similarities* with the structural system of the Ponte Morandi (Polcevera Viaduct) that collapsed on 14 August 2018 in Genova.
The involvement of the infrastructuResilience group
After invitation from the regional Governor of Western Macedonia – Greece, a visual inspection of the landmark Lake Polyphytos Bridge (Greek: Γέφυρα της λίμνης του Πολυφύτου) at Servia, Kozani had been conducted with the Governor of Western Macedonia and his consultants in early January 2020. The #infrastructuResilience of the university of Surrey was there to offer consultation and opinion on the significance of what was told to be a vertical displacement of the deck, mainly along the part of the bridge that was constructed by the balanced cantilever method. The visual inspection revealed large vertical displacements of the balanced cantilever spans of the bridge, and thus urgent preventive measures were considered to be appropriate and taken at this stage. The measures are aiming at mitigating the risk of failure of the landmark and safeguarding the safety of end-users and citizens. The urgent measures are twofold: 1) reduction of maximum vehicle load and maximum speed and 2) connection of the Gerber simply support 40 m-long spans with the 30 m long cantilevers of the bridge. The first measure aims at reducing the load and the second will reduce the risk of having the Gerber beams unseated. However, the reduction in the risk is very small as the main issue seems to be the vertical deflection of the cantilever downward, and this is the main conclusion of the inspection, whilst the reduction of the maximum vehicle load and speed seems to represent a very small portion of the total load of the deck. The photographs below show left: a view of the bridge (from Kozani to Servia), middle: the visual inspection, right: the problem as confirmed on site.
In continuation to our involvement with the inspection of the High Bridge of Servia (Polyfytos Lake Bridge), Stergios spoke to the national tv channels ERT1 and ERT3 (@ time 1h35min) analysing “what’s next” for this landmark bridge of high importance and how this affects the resilience of the network, the region and beyond.
Our involvement with the inspection of the bridge has been covered extensively by local and international media.
Press releases and reports:
tovima.gr kathimerini.gr ethnos.gr ert.gr
zougla.gr makthes.gr msn.com greekcitytimes (en)
eleftherostypos.gr neoskosmos.com (Australia)
* The similarity is the use of Gerber simply supported spans on cantilevers. Also, the understanding is now that the preliminary interview, on 15 August 2018, one day after the collapse of the bridge (see Stergios’s BBC interview here) has provided a relatively accurate comment: “…some environmental factors may have caused this bridge to deteriorate early… rust can be seen at the top of the tendons” is in accordance with the detailed research published 16 months later by Calvi et al. (2019): “The loss of a stay seems to be the final cause of collapse…The possible initial cause of the collapse may thus be related to fatigue problems in the tendons near the tip of the antenna, or by deterioration of the connection between stay and transverse link.” The latter raises concerns with regard to the design of the system of protection of the tendons adopted by professor Morandi.
