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Genoa's Morandi Bridge to be Demolished

Tuesday, November 13, 2018

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Three months after the collapse of Genoa’s Morandi Bridge, testing of debris from the site has begun, and a demolition date for what remains of the span has been set.

The testing of the debris will help determine what caused the collapse. Genoa Mayor Marco Bucci announced that the demolition of what remains of the Morandi Bridge will begin Dec. 15, which will make way for a new overpass over the city.

Bridge Collapse History

Late in the morning on Aug. 14, lightning struck the Morandi Bridge. At the time, 35-mile-per-hour winds were recorded with a thunderstorm moving through the area. A 200-meter (656-foot) section of the prestressed concrete span collapsed, creating a gulf between two sections of the bridge.

The cable-stayed concrete bridge, also known as the Polcevera Viaduct, completed in 1968, was designed by Italian civil engineer Riccardo Morandi. According to the website Retrofutur, the bridge is characterized, as are other Morandi structures, by thin prestressed concrete girders and relatively few stays. Three A-shaped concrete pylons hold four prestressed stays apiece. The website has chronicled numerous projects over the years to reinforce the structure, including steel sheaths over the concrete pylons.

While experts believe that structural weakness contributed to the collapse, previous warnings about the condition of the bridge were issued years before disaster struck. For example, in 2012, the leader of Genoa's business federation noted that the bridge could collapse within 10 years. In 2011, a report from Autostrade per l'Italia, the operator of the A10 highway that ran over the bridge, warned of intense decay.

Morandi penned his warning partially due to the perplexity of the degradation problem—the amount of corrosion that the bridge exhibited even early on wasn't seen on similar structures in different environmental circumstances. At the end of August, well-known Italian architect Renzo Piano offered to help design a replacement structure signifying rebirth and redemption for the affected area.

Debris Testing

According to New Civil Engineer, experts at the Federal Laboratory for Materials Science and Technology will study the debris from the collapse to determine if corrosion was a contributing factor. Previously, New Civil Engineer sources, who had been close to the investigation, noted that evidence of corrosion and damage had been found on the main stay cables. This suggests failure, though the cables were encased in concrete to protect them from the elements.

Another potential cause of the collapse was rain eroding ground out from under the tower, weakening its foundations. Strengthening work was being carried out on the foundations at the time of the incident, noted Autostrade.

Demolition Scheduled

Access to the bridge is still restricted as investigations continue. Demolition work, which is slated to take a month, will begin once site access is opened. Structure removal will begin with the west pillar, and construction of the new bridge will start as demolition moves along the east side.

Currently, many are speculating that the new bridge will implement Piano’s design, but the mayor did not confirm this idea. Other plans for a new structure have also been proposed, among them a tunnel. Otherwise, in the interim, traffic patterns have been restructured.

   

Tagged categories: Accidents; Bridges; EU; Europe; Fatalities; Government; Infrastructure; Program/Project Management

Comment from Tom Schwerdt, (11/13/2018, 9:33 AM)

Corrosion can still occour on steel inside concrete - that's one very common reason for spalling of reinforced concrete. Corrosion is more likely/proceeds more rapidly with higher levels of chlorides and lower pH (less alkalinity) - Lowering pH is a natural process with concrete as it reacts with carbon dioxide from the air. Densified, low porosity concrete slows the penetration of carbon dioxide.


Comment from Scott Youngs, (11/13/2018, 12:04 PM)

"Corrosion can still occur on steel inside concrete" I was thinking the same thing when I read the comment "though the cables were encased in concrete to protect them from the elements"


Comment from Michael Halliwell, (11/14/2018, 6:17 PM)

Yup, concrete is a porous medium: if done right, it might slow the progress of degradation by limiting exposure...if not, it can end up trapping water and chlorides with the metal and accelerate the corrosion.


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