Dangerous Bridges (02:19)

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In August 2018, an 800 ft. section of the Ponte Morandi collapses, killing 43 people. More than 60 bridges around the world have collapsed in the last decade; the U.S. has over 47,000 structurally deficient bridges.

Morandi Bridge Collapse (05:03)

Many trucks that transport goods from the port of Genoa travel along the E80 highway. Davide Capello and Gianluca Ardini recall traveling the road and crossing the Morandi when a section of the bridge collapsed; 27 vehicles fall.

Disaster Rescue (02:17)

Rescuers free Ardini from his truck that hangs in the collapsed bridge tower. Firefighters recover the last body after four days; 43 people die in the disaster. Engineers seek to discover the cause and identify other bridges at risk.

Structurally Deficient Bridges (02:06)

World War II operations destroy thousands of bridges in several countries. In the U.S., the "golden age" of the car pushes road development. Many concrete bridges are nearing the end of their useful design life; over 47,000 are deficient.

Ponte Morandi Inquiry (04:37)

Engineers seek to identify the origin of failure and cause of collapse. They examine Riccardo Morandi's cable-stayed bridge design.

Origin of Failure (03:20)

The Ponte Morandi opens in 1967 and catastrophically fails in 2018. Engineers investigate what part of the bridge failed first; see a reconstruction. A CCTV video is important to the criminal investigation.

Traffic Loads (05:50)

Many bridges experience increasing traffic volumes. A design error results in the collapse of the I-35W Bridge in 2007. Riccardo Morandi designs the Ponte Morandi to support a significant amount of weight; the load level is light the day of its collapse.

Single Point Failure (05:40)

The Silver Bridge opens in 1928; Peggy Huber recalls its collapse in 1967. Investigators determine corrosion and the resulting fracture in an eyebar as the cause of failure. Approximately 18,000 bridges in the U.S. are fracture critical. Modern cable-stayed bridges have a fan of cables.

Steel and Concrete (07:30)

Forensic engineers examine evidence from the Ponte Morandi collapse and identify corrosion on some steel cables; concrete should prevent rust. In 2011, experts determine the Hammersmith Flyover is at risk of collapse; learn about its construction and repair.

Bridge Maintenance (05:49)

Scientists examine pieces of the Ponte Morandi and discover cavities that led to corrosion. Autostrade uses RIMT and asserts cable stay failure is not the primary cause; a study suggests unreliability. Autostrade states RIMT2 allows accurate assessment and submits plans to replace cable stays in 2017.

Aging Infrastructure (02:49)

Prestressed concrete bridges are a focus of concern; inspectors find a 90ft crack in the Elsen Bridge and close the structure. Experts consider the likelihood of a bridge collapse in the U.S. Modern engineering allows better maintenance.

City of Bridges (04:28)

Pittsburgh, PA has over 400 bridges. The cables on the Philip Murray Bridge exhibit corrosion and engineers implement a dehumidifying solution. Innovative technologies can reduce the risk of bridge collapses. Experts design a new bridge in Genoa.

Credits: Why Bridges Collapse (00:51)

Credits: Why Bridges Collapse