Bridges are fascinating – Both from a design and engineering point of view. They can look spectacular in the nights and shortens the distance between two points by a great degree. Even though bridges have been in use for 100s of centuries, every new bridge project starts the design stage from zero. This is because there are so many variables to consider when designing a bridge.
But as with all beautiful things, bridges fail spectacularly. There have been many incidents in the history of engineering where completely fine looking bridge designs failed. When bridges fail, it can lead to injuries, loss of life, property damage and an ugly failure in the engineer’s portfolio. While natural causes are sometimes at play, most failures can be traced back to human and material errors.
So let’s have a look at the 6 common reasons why some bridges fail–
Some bridges have certain restrictions on the load limits. Ignoring these limits can lead to serious damages to the structure. Even if an immediate collapse does not occur, there can be developing signs of failure caused by regular overloading.
Analysts have found overloading to be the 3rd most common cause of failures in bridges, followed by old age. So combine old age and overloading and you have the perfect recipe for a disaster.
All things come to an end and so do bridges. All structures have a designated lifespan. After which the signs of failure starts to creep in. The average age of Highway Bridge is around 70-80 years in the optimal conditions. When the signs of aging start to show up, then a structural failure analysis can reveal details of the expected structural life.
It’s best to replace or demolish old bridges when time remains. It is also important to note that optimal conditions also include the maintenance and servicing of the bridge. Regular maintenance can help to eliminate the issue before they take complete form.
Sometimes it is the incompetence, negligence and poor engineering that becomes the cause of the issue. Many examples have been published in the history books that have marked as poor designing as the culprit of the failure. Fortunately, modern computational and simulation techniques have helped to curb the incidents.
“Galloping Gertie”, the Tacoma Narrows Bridge is a prime example of this issue. Gusts of wind made this suspension bridge kiss the water in pieces.
A good design is as good as the materials used. Blame it on cost-cutting, corruption, laziness or lack of technical knowledge – whatever you feel fancy to choose, the outcome is the same. Poor materials will always fail over time.
Bridges are subjected to a lot of forces – both man-made and natural. That’s why quality and safe materials are so crucial.
Ships hitting the pillars, cars committing suicides off the rails, trucks leaning on to the sides, or trains derailing are some of the transport accidents that cause bridges to fail. They may or may not lead to complete collapse but surely lead to failures. Quick repair and reconstruction are absolutely necessary in such cases.
Finally, it’s nature that wants to spoil an engineer’s efforts. Earthquakes, floods, hurricanes, ice, or just the land become the common sources of failures. While modern bridges are designed to withstand many natural elements, many small road bridges or walkways are not treated with the same construction techniques. That’s why many small bridges collapse even in the faintest of a natural disaster.