Arch bridges have abutments that are curved and shaped like arches (hence their name) on either end. These abutments serve as base points for the weight of the people, animals, or vehicles that would cross the bridge. Arch bridges have been around for a long time; in fact, the oldest known arch bridge was built around 1300 B.C. The Etruscans and the ancient Greeks constructed arch bridges, but it was the Romans who saw the potential of these bridges and used their design in building numerous aqueducts as well as stone and timber bridges.
As decades and centuries passed, people continued to build arch bridges, improving the design to suit their needs and reflect the architectural style that’s in vogue at the time. Arch bridges have gained popularity and admiration because of their strength and pretty appearance, but they also draw criticism because of a few drawbacks. Read on to know about the pros and cons of arch bridges.
List of Pros of Arch Bridges
1. They have excellent strength.
Arch bridges are some of the strongest types of bridges because of their unique arch design. These bridges are built with a keystone (a wedge-shaped stone that helps lock all the other stones into place) in the middle of the arch. When people or vehicles cross the bridge, the keystone distributes their weight by pressing on the stones beside it which, in turn, passes the weight to the stones beside them. The weight is distributed evenly instead of just staying in the middle portion of the bridge, which can weaken and become damaged over time when exposed to too much pressure.
2. They get stronger as years pass.
Other bridge types get weaker as time goes by, but this isn’t the case for arch bridges. In fact, these structures get stronger over time because of their design. As mentioned above, the keystone distributes the weight of the bridge’s load to the stones beside it, which pass on the weight to the stones beside them. This “domino effect” continues until the weight reaches the abutments, which pass the pressure on to the ground. Illustrating Newton’s Third Law of Motion (“For every action, there is an equal and opposite reaction”), the ground pushes back up into the abutments, which push on the stones until the force reaches the keystone. This process, in effects, “locks” each stone in place and makes the bridge stronger the more it gets used.
3. They can be made of any kind of material.
Arch bridges can be made of any material that can withstand pressure. Ancient arch bridges were made of stone (both cut and uncut), and later versions were constructed from bricks. Modern arch bridges are made of steel and reinforced concrete.
4. They look attractive.
Since they have been around for a long time, arch bridges have become associated with romantic poems and heroic stories. They have become the meeting place of fictional lovers and the dying places of fictional heroes and villains. Even real-life arch bridges have gained popularity for being charming and enchanting; the Stone Arch Bridge in Minneapolis, for instance, has become known as the most romantic spot in the city.
List of Cons of Arch Bridges
1. They are difficult to build.
Designing arch bridges can be challenging since there are lots of factors that have to be taken into account. Building them can also be time-consuming, and many workers are required to put them up.
2. They require stronger supports.
Arch bridges need stronger supports than ordinary bridges would since, as explained above, their structural integrity greatly depends on how sturdy their abutments are and how they’re well-set into the ground. This is one of the reasons why arch bridges take a lot of time and effort to be built; if engineers want to have bridges that can withstand a lot of load and can last for years, they must first build supporting structures that are stronger than normal.
3. They have limited spans.
By their own nature, arches need to have starting and ending points. Unlike other designs, they just can’t go on for long stretches of distance; they need to stop at a certain point or else they’d become too weak to handle their load. This is one of the limits of arch bridges: a single arch won’t be enough if a long distance has to be covered or if the bridge needs to support a lot of weight and traffic. If this is the case, the bridge must be built with several arches or constructed with reinforcing material that will allow it to withstand the pressure.
4. They can’t be built just anywhere.
Several requirements must be met before an arch bridge can be built in a certain spot. One of these is the condition of the ground, which has to be strong and compact enough to support the force that would be distributed along the bridge and down to the abutments. It’s important to note, though, that the design and materials of modern bridges allow them to tolerate pressure within their structure and make it possible for them to be built on weaker ground.
5. They can be expensive.
As mentioned above, arch bridges require lots of time and labor, which can translate to thousands of dollars. It also requires the expertise of numerous engineers and builders which, again, equates to a substantial amount of money. Of course, the materials that are used to construct the bridge also contribute to the overall cost; the higher the quality of the materials, the more expensive the bridge would be.
6. They need regular maintenance.
Arch bridges become stronger over time, but this doesn’t mean that they should just be left on their own. In fact, they need more frequent repair and maintenance than other kinds of bridges since their flexible design makes them more prone to cracking and tearing when exposed to harsh elements. The costs that come from keeping them in good shape can make them more expensive over time.
Arch bridges have several benefits in terms of aesthetic value and structural integrity, but it also has its drawbacks in the form of cost, time, and labor. Because of this, engineers and other experts should carefully the pros and cons of arch bridges and decide if they’re the right choice for a certain project.
Natalie Regoli is a child of God, devoted wife, and mother of two boys. She has a Master's Degree in Law from The University of Texas. Natalie has been published in several national journals and has been practicing law for 18 years.