Last week’s poll: minimising chances of bridge collapse disasters

Engineer readers think that cable corrosion monitoring is key to preventing tragedies like last month’s collapse of the Morandi bridge in Genoa

We received 314 responses to last week’s poll on the collapse of the Morandi bridge in Genoa. There was no clear majority for any of the responses offered, but the largest group of respondents, 45%, backed the monetary installation of sensors to monitor cable corrosion in suspension-type bridges (including cable-stayed bridges, of which this was an example). The next biggest group of respondents, 27%, did not support any of our suggestions. Within a hair’s breadth of this, 26% chose the need for regulations to acquire access to load-bearing structures, while the smallest group, 2%, thought that better standards for lightning and wind shear protection would be most effective.

We published 21 comments to this poll. These tended to focus on the flaws in the bridge design. Bruce Renfrew made the point succinctly: “It was simply a flawed design – I’m surprised it passed initial scrutiny and that it lasted as long as it did.” Alfredo Clausen was more specific in his criticisms: “The catastrophe started when the (excessively) acclaimed designer became obssessed with the (ab)use of prestressed and reinforced concrete, so much that he choose to use prestressed concrete stays,” he said. “one thing is clear: he commited the sin of overconfidence (like many designers that end up feeling perfect OK with their criteria), and used TOO FEW stays, It seems Morandi disrespected any sense for the need of REDUNDANCE, and that my friends is a CAPITAL SIN in a designing engineer! Morandi can be pardoned in respect of the wrong belief that concrete was impervious to degradation, to some extent. But his use of too few stays and his insistence of using prestressing for those stays that mostly work in tension, cannot be accepted as good engineering practices.“

Some commenters raised the point that corruption may have played a role in the disaster. “Corruption is the all-pervasive problem. The love of money is the root of all evil. If cost-cutting is an overarching parameter of design, construction AND maintenance, you create the perfect storm, not the perfect bridge (or any infrastructure for that matter).” Said David Smart, who also pointed out that only four cables from each tower was inadequate support for the road deck, considering that the second Severn Crossing between England and Wales has 120 cables from each tower. A reader using the name “To be Frank” further pointed out that technological solutions may not be sufficient. “Install all the Sensors and monitoring you want. If the collected data is not analysed and the results truly acted upon they will all be worthless,” he said. “Produce endless Standards and Regulations. If they are not implemented and thoroughly checked and tested for compliance, they too will be worthless.”

Please continue to send us your opinions on this subject.