“the 45 year – old and 1372 m – long bridge that connects the city of Kozani with Larisa, Athens & national road network”
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.
Generation of digital twin (15 February 2020)
The digital twin of the Lake Polyfytos Bridge was based on state-of the art photogrammetry methods. For the extended survey and the construction of the digital twin more than 1000 high resolution photos were taken per 100m along the length of the bridge, both nadir and oblique in various angles in fully automated missions. Additionally, another 10 ground control points and check points per 100m were defined, for improving the accuracy and consistency of the acquired data. Also, surveying measurements of the structure were taken by making use monitoring-grade total station and high-precision multi-hour static GNSS measurements of its’ stationary points. All photographs, in raw format, were initially processed through photo-editing software for enhancement and then used in photogrammetry software. The point cloud generated has a point-to-point spacing of 7mm and is being used for assessing the current condition and monitor potential evolution of deterioration and structural defects. The most critical structural components of the bridge is currently measured with a laser scanner. The survey was conducted by Yannis Karnaris, Surveying and Geomatics Engineer, PhD in Drone Photogrammetry
Briefing to the W. Macedonia regional government of Greece (3 Feb. 2020)
Presentation by Dr Stergios Mitoulis on the risk and resilience of the Polyfytos/Servia Bridge and the resilience of the region.
A full-room during the 3rd February briefing to the W. Macedonia regional government of Greece on the bridge. The condition of this landmark bridge of high importance and its impacts and interdependences between the local network, energy asset functionality, businesses and society was extensively discussed yesterday.
The infrastructuresilience groups was there to provide research-based consulting toward decision making on matters raised by engineers, the local Governor and his consultants, the mayors of Servia and Velventos and representatives from other parties of the regional government. Currently the team of the infrastructuresilience group works intensively to provide a cross-disciplinary approach to the matter and to the impacts on the local energy and transport network and other utilities to alleviate impact and underpin the resilience of the region.
Second inspection of the landmark Polyfytos Lake Bridge of Servia
The Polyfytos Lake Bridge of Servia, was inspected recently to provide further insights to what was visually found to be vertical displacements of the deck of the balanced-cantilever part of the structure. This second inspection followed the topographic survey of the asset that was actioned with a UAV (drone) and geodetic total station and levels of the bridge deck were identified, preliminarily assessed and recorded, whilst a 3D digital twin of the bridge with its defects is underway.
The inspection was an organised endeavor to better understand the condition of the structure and discuss with Dr Telemachos Panagiotakos/DENCO Structural Engineering these first findings. This second endeavour is a preliminary and preparatory action.
Part of this inspection was a preparatory assessment of the pathways for communicating the potential risks to the local societies and businesses and the assessment of the potential impacts. This included the communication of the engineering findings to the local authorities and stakeholders.
The resilience of the bridge, the road network and the interoperabilities with energy assets are currently under discussion.
The infrastructuresilience.com group was there and results of the ongoing H2020 projects #Briface and #TRANSRISK and other research projects #ResilienTTS were communicated to the operators and the national TV #ERT1
First inspection of the landmark Polyfytos Lake Bridge of Servia
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:
* 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.