Before the fall there was already a lot of talk about the constant, excessive maintenance and repairs needed by the bridge; there was discussion if the best way to go forward was a major overhaul or just demolition (of course such talk could have gone on for years or decades before anything was made).

In the '80s the support structures were already reinforced and apparently it took years of filling the subsidences in the asphalt surface for it to stabilize and provide a level surface for the cars.

I'm not a structural engineer and I am in no position to judge, but there definitely was the suspicion that the design of the bridge was flawed, even before today.

>I'm not a structural engineer and I am in no position to judge, but there definitely was the suspicion that the design of the bridge was flawed, even before today.

The bridge was - at the time - a bleeding edge of concrete technology, designed by the greatest expert in concrete (and pre-compression) in Italy (and probably in the world), Riccardo Morandi.

He designed also the Maracaibo Bridge:

https://en.wikipedia.org/wiki/General_Rafael_Urdaneta_Bridge

Allow me to doubt that the design had structural flaws, though it is true that at the time some aspects of long span pre-stressed concrete structures were not yet fully undestood, namely creep and shrinkage:

https://en.wikipedia.org/wiki/Creep_and_shrinkage_of_concret...

Which have definitely increased the need for maintenance, shortening the expected working life of similar structures.

However from the little it can be seen from the photos that have been posted here and there, it seems like the initial point of failure was not the bridge (meaning the deck) but rather the pier, causing the two adjoining spans to collapse.

Experts do make mistakes sometimes

The Kingston Bridge in Glasow, which opened in 1970, has had to have a huge amount of work done over the years - there were problems with both the original design, the actual construction and the face it was carrying far more traffic than expected:

https://en.wikipedia.org/wiki/Kingston_Bridge,_Glasgow

Edinburgh's Forth Road Bridge was also partially closed in 2015

https://en.wikipedia.org/wiki/Forth_Road_Bridge#Structural_i...

According to news reports, likely immediate causes include lightning striking one of the pillars, wind and overload. It seems quite certain that the bridge was somewhat decrepit, and some media report that consolidation work was in progress.

How can lightning cause a bridge to collapse?

The average lifespan of a bridge is about 70 years.

And requires no maintenance?

They definitely require routine maintenance and inspection.

The Nondestructive Testing article I linked to in another comment said "significant environmental damage requiring repair typically occurs before the average bridge reaches mid-life."

It would be very interesting to know how bridge metrics (length, load specification, etc.) relate the longevity. Of course, some bridges last for centuries, but some last for decades. This is an order of magnitude!

Spoiler: they don't, yet they do, Theseus' ship-style. For all the centuries-old bridges still in use around here, there's only a few bits and pieces left from the original, the rest has been replaced multiple times over as a part of maintenance.

The difference here is probably maintainability: for a stone arch design, you can prop it up for safety, replace a few stones, and voila, like new. For a cable-stayed and/or concrete design...not really. In other words, the bridges that have "lasted for centuries" have hot-swappable parts ;)

Isn't that just a function of when most highway construction took place in Europe and the US?

Lifespan, not age. Most bridges where built after 1945 with a life expectancy between 70-75 years.

https://www.nde-ed.org/AboutNDT/SelectedApplications/Bridge_...