What’s their bottom line here ?
We’ve seen bridge collapses. It’s a nightmare of mine that is shared by literally everyone in America.
We can do fast, but can we do good for a change ? Why is it older bridges throughout the Northeast lasted for over a century, but these newer Eisenhower bridges can’t seem to live up to that legacy ?
Speaking just generally, the older bridges that you refer to were designed in the day when slide rules, logarithm tables and various engineering tables were used. Lumped in with this, material specifications for steel and concrete were not as precisely uniform. To compensate for the lower precision of design, materials and construction techniques, safety factors were greater. In other words, the bridges were way over built.
This does not imply at all though that there is anything inherently deficient with modern designs that can use computer optimization and graphical tools achieve performance targets more efficiently with regards to materials and constructability.
No matter if an older design or modern, the keys to longevity are inspection, maintenance and repair. Short on any of these and you loose service life at the least and catastrophic failure at the worst.