Why Did the Morandi Bridge Collapse, Killing 43 People?

Why did Italty’s Ponte Morandi (Morandi Bridge), built in 1967, collapse?

The bridge was designed by Riccardo Morandi. It is similar to his earlier 1957 design for the General Rafael Urdaneta Bridge, located at the outlet of Lake Maracaibo in western Venezuela, which partially collapsed in 1964 when the tanker Esso Maracaibo collided with the approach spans.

Morandi’s cable-stayed bridges are characterised by a prestressed concrete structure for the piers, pylons and deck, very few stays, as few as two per span, and a hybrid system for the stays constructed from steel cables with prestressed concrete shells poured on. The concrete was only prestressed to 10 MPa, resulting in it being prone to cracks and water intrusion, which caused corrosion of the embedded steel.

On August 14 the Morandi bridge in Genoa collapsed partially. A 200 meter long roadway section fell 15 meter on the below apartment houses.

In the course one of the massive pylons collapsed as well. The tragedy claimed the lives of 43 people.

This bridge was part of the A10 motorway that is the main link between the Italian and French riviera.

This accident is one of the big tragedies that come unexpectedly and live long in our memories. It it makes us ponder over the safety of similar old structures that eventually would need urgent repair.

The reason of the collapse of the Morandi bridge is currently hotly debated.

Much hints to a lack of maintainance and a resulting failure of structural member. But also the heavy weather conditions with a thunderstorm and a lighting impact are often blamed.

Most theories point to the failure of one of the suspension cables.

The BCB was used to systematically analyze the presumed collapse episode and debris shape for the failing of each of the four suspensions. The simulations were performed by Kostack Studio.

Simulation of the Morandi bridge collapsed in Genoa, Italy, in 2018, performed with the Bullet Constraints Builder (BCB) structural simulation software for Blender. The model was built from plans true to scale. Reinforcement information was estimated in part from photos of the destroyed bridge.

In order to narrow down the likely collapse scenario this video includes simulation results for different initial failure points. The characteristics of the debris heaps in comparison to reality often can provide an indication on what has probably happened.

Source: Laurea University

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