Depends on the bridge. Steel and concrete bridges can last for at least 100 years. But it depends on the environment, its expected use, the construction, design. Some famous major bridges failed early due to poor design or poor construction, but many still fail due to lack of maintenance.
The average age of a bridge in the USA is 43 years. But we also have an epidemic of unmaintained bridges.
No bridge made today is designed to last indefinitely. Many different forces will degrade the bridge over time, even with maintenance. Steel stresses weaken it over time. Concrete weathers over time due to salt, chemicals, water, wind, and the steel reinforcements tend to corrode eventually.
Stone bridges may last for an exceptionally long time, but their weight and expense makes them only useful in limited applications, typically as small rail overpasses. Ones that were designed for horse and buggy end up slowly failing as heavier trucks and cars in traffic weaken them.
The same fate lies for timber bridges. When well maintained they can last for 75 years, but it's expensive and requires certain skills. They were also mostly designed before heavier cars and trucks, and for less traffic. Most famous covered bridges today are being closed to traffic due to increased wear.
According to https://www.fhwa.dot.gov/bridge/, the federal government oversees more than 610,000 bridges in the USA. There are a lot of unmaintained small bridges. But I'd hope that the major ones get more attention.
If it is a famous bridge, it seems possible that they’ve done some special extra maintenance, replace more wear-and-tear bits that would normally fail. Eventually you probably get the tourist attraction of Theseus.
Sure, and there's 100's of thousands of replaced bridges that don't immediately spring to mind.
Though to be clear designed to last 50 years isn't the same as saying it will only last exactly 50 years, or that theirs nothing you can do to extend a bridges lifespan if it's replacement is running a little late.
0xbadcafebee|1 year ago
The average age of a bridge in the USA is 43 years. But we also have an epidemic of unmaintained bridges.
No bridge made today is designed to last indefinitely. Many different forces will degrade the bridge over time, even with maintenance. Steel stresses weaken it over time. Concrete weathers over time due to salt, chemicals, water, wind, and the steel reinforcements tend to corrode eventually.
Stone bridges may last for an exceptionally long time, but their weight and expense makes them only useful in limited applications, typically as small rail overpasses. Ones that were designed for horse and buggy end up slowly failing as heavier trucks and cars in traffic weaken them.
The same fate lies for timber bridges. When well maintained they can last for 75 years, but it's expensive and requires certain skills. They were also mostly designed before heavier cars and trucks, and for less traffic. Most famous covered bridges today are being closed to traffic due to increased wear.
btilly|1 year ago
unknown|1 year ago
[deleted]
onlyrealcuzzo|1 year ago
mango7283|1 year ago
bee_rider|1 year ago
Retric|1 year ago
Though to be clear designed to last 50 years isn't the same as saying it will only last exactly 50 years, or that theirs nothing you can do to extend a bridges lifespan if it's replacement is running a little late.