applied sciences Article Causes of the Collapse of the Polcevera Viaduct in Genoa, Italy Janusz Rymsza Road and Bridge Research Institute, 03-302 Warsaw, Poland; [email protected]; Tel.: +48-22-390-01-07 Abstract: The article investigates the causes of the Morandi viaduct collapse in Genoa. This three- span viaduct was a part of the A10 motorway leading to Savona. The structure design of the viaduct supports and diagonal stay cables was unique. The viaduct included three cable-stayed system, each supported a three-span continuous beam by two sets of prestressed concrete cables on the two sides of the pylon across the width. The pair of V shapes piers supported upside-down V pylons that supported the top ends of two pairs of diagonal stay cables. The stays were constructed from steel cables with prestressed concrete shells poured on. This article provides information on the technical condition of the viaduct and the way of strengthening the cables in the early 1990s. At that time, the author of the article visited the structure. In August 2018, the viaduct collapse occurred, and one of the structure supports collapsed. In June 2019, during the demolition process, the other two supports were destroyed. Since in Venezuela and Libya there are still two more bridges with a structure similar to that in Italy, the concept of strengthening the structure, as proposed by the author of the article 25 years ago, may still be useful. Keywords: Morandi bridge; Polcevera Viaduct; corrosion; collapse; bridge; truck loads; collapse of Polcevera Viaduct; large pre-stressed bridge structures; Prof. Morandi Citation: Rymsza, J. Causes of the Collapse of the Polcevera Viaduct in 1. Introduction Genoa, Italy. Appl. Sci. 2021, 11, 8098. 1.1. General Information https://doi.org/10.3390/app The Polcevera Viaduct in Genoa was designed by Riccardo Morandi (1902–1989), a 11178098 professor of civil engineering at the universities in Rome and Florence. Prof. Morandi had designed many civil buildings and he was an avid supporter of the use of pre-stressed Academic Editors: Daniel Dias and concrete in engineering structures, including bridges. In the 1960s and 1970s, he designed Giuseppe Lacidogna three similar pre-stressed bridges of unique structure. These were: bridge over Lake Received: 23 July 2021 Maracaibo in Venezuela (235 m long; 1962), Viaduct in Genoa (~208 m long; opened on the Accepted: 24 August 2021 4 September in 1967), and the Wadi Kuf Bridge in Libya (282 m long; opened in 1971). Published: 31 August 2021 Extensive information about the viaduct in Genoa can be found in the study by Morandi in 1968 [1], while the design parameters of the three bridge structures designed Publisher’s Note: MDPI stays neutral by Prof. Morandi were described by Troitsky in 1977 [2]. Prof. Morandi received many with regard to jurisdictional claims in international awards for his design of buildings and bridges, including the honorary published maps and institutional affil- doctorate from the Technical University of Munich in 1979. iations. The bridge in Genoa consisted of a three-span viaduct and a multi-span overpass, which connected to the viaduct from the west. The viaduct was constructed over ~80 m wide Polcevera river, from which it derived its official name. The bridge structure was built over the railway line linking Genoa with Milan, the industrial plants, and residential Copyright: © 2021 by the author. buildings. The viaduct carried the A10 motorway from Genoa to Savona, transferring Licensee MDPI, Basel, Switzerland. traffic of a large number of heavy trucks. The carriageway had four lanes, two in both This article is an open access article directions. The view of the Polcevera Viaduct from the north-east is shown in Figure1. distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Appl. Sci. 2021, 11, 8098. https://doi.org/10.3390/app11178098 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, 8098 2 of 2021 Appl. Sci. 2021, 11, 8098 2 of 21 Figure 1. View of Polcevera Viaduct from the north-east (Morandi, 1968). FigureFigure 1. 1.View View of of Polcevera Polcevera Viaduct Viaduct from from the the north-east north-east (Morandi, (Morandi, 1968). 1968). 1.2. Static Scheme of the Bridge Structure 1.2. Static Scheme of the Bridge Structure 1.2. TheStatic bridge Scheme consisted of the Bridge of 11 Structure spans with the following length: 43.00 + 5 × 73.20 + 75.313 + 142.655TheThe bridge+ bridge 207.884 consisted consisted + 202.50 of +of 1165.10 11 spans spans = 1,102.452 with with the the m. following following The structural length: length: scheme 43.00 43.00 + of 5+ × 5the ×73.20 73.20 viaduct + + 75.313 75.313 and +the+ 142.655 142.655 multi-span + + 207.884 207.884 overpass + + 202.50 202.50 are+ shown+ 65.1065.10 ==in 1102.4521,102.452 Figure 2. m. m. The The structural structural scheme scheme of of the the viaduct viaduct and and thethe multi-span multi-span overpass overpass are are shown shown in in Figure Figure2. 2. Figure 2. Structural scheme of the viaduct and the multi-span overpass (Morandi, 1968; dimensions in m). Figure 2. Structural scheme of the viaduct and the multi-span overpass (Morandi, 1968; dimensions in m). Figure 2. Structural scheme of the viaduct and the multi-span overpass (Morandi, 1968; dimensions in m). The static scheme of structures of the viaduct and the multi-span overpass consisted of The static scheme of structures of the viaduct and the multi-span overpass consisted a multi-span frame with V-type supports (Figure3a) and spandrel beams with cantilevers of a multi-spanThe static framescheme with of structures V-type supports of the vi(Figureaduct and3a) andthe multi-spanspandrel beams overpass with consisted cantile- on which the suspended spans were supported (the piers of the previously designed bridge versof a on multi-span which the frame suspended with V-type spans weresupports support (Figureed (the 3a) piersand spandrel of the previously beams with designed cantile- in Venezuela are of the X-type [3]). Overpass spans were supported at the cantilevers of vers on which the suspended spans were supported (the piers of the previously designed bridgethe V-type in Venezuela piers Nos. are 3 toof 8.the Whereas X-type [3]). the structureOverpass of spans the three were other supported piers ofat thethe viaductcantile- bridge in Venezuela are of the X-type [3]). Overpass spans were supported at the cantile- vers(Nos. of 9, the 10 V-type and 11) piers was anotherNos. 3 to type. 8. Wherea A pylons the supporting structure twoof the pairs three of cablesother piers was addedof the vers of the V-type piers Nos. 3 to 8. Whereas the structure of the three other piers of the viaductto each (Nos. of the 9, framed 10 and support.11) was another The pylons type. of A thepylon viaduct supporting are shown two pairs in Figure of cables3b. Thewas viaduct (Nos. 9, 10 and 11) was another type. A pylon supporting two pairs of cables was addedthree reinforced to each of concrete the framed pylons support. of the The portal pylons shape of were the viaduct 90 m high are above shown the in terrain. Figure The3b. added to each of the framed support. The pylons of the viaduct are shown in Figure 3b. Thecross-section three reinforced of the bridgeconcrete span pylons was of a threethe portal cell pre-stressed shape were 90 concrete m high box. above The the spandrel terrain. The three reinforced concrete pylons of the portal shape were 90 m high above the terrain. Thebeam cross-section in the longest of span,the bridge between span the was forked a three columns cell pre-stressed of support concrete No. 10, hadbox. aThe length span- of drelapproximatelyThe beam cross-section in the 45 longest m,of the and span, bridge the between length span ofwas the the aforked cantileverthree columnscell pre-stressed was of ~65 support m. concrete The No. 18 10, m box. widehad The a bridgelength span- ofdeckdrel approximately wasbeam positioned in the longest45 m, at anand span, elevation the between length of of ~45 the the mforked cantilever above columns the was terrain. of~65 support m. The No. 18 m10, wide had abridge length deckof approximately was positioned 45 at m, an and elevation the length of ~45 of them above cantilever the terrain. was ~65 m. The 18 m wide bridge deck was positioned at an elevation of ~45 m above the terrain. Appl. Sci. 2021, 11, 8098 3 of 21 Appl. Sci. 2021, 11, 8098 3 of 20 (a) (b) FigureFigure 3. 3.(a()a Overpass) Overpass support support (longitudinal (longitudinal an andd cross-section) cross-section) (Morandi, (Morandi, 1968). 1968). (b ()b Viaduct) Viaduct support support (longitudinal (longitudinal an andd cross cross section) section) (Morandi, (Morandi, 1968). 1968). Appl. Sci. 2021, 11, 8098 4 of 21 Appl. Sci. 2021, 11, 8098 4 of 20 1.3.1.3. Diagonal Diagonal Stay Stay Cable Cable Structure Structure According According to to OnOn both both sides sides of of each each pylon, pylon, two two cantilevers cantilevers of of prestressed prestressed concrete concrete and and steel steel box box werewere fixed fixed to to the the pylons. pylons. These These cantilevers cantilevers were were supporting supporting the the suspended suspended span. span. The The steel steel cablescables with with prestressed prestressed concrete concrete shells shells poured poured on on had had a rectangulara rectangular cross-section cross-section and and a a formform of of a compositea composite steel steel and and concrete concrete element, element, asingle a single at at the the top top of of the the pylon pylon and and divided divided intointo two two equal equal parts parts at at the the deck deck level.