Most people drive, walk, or even bike across bridges daily as they make their way to work, school, or the grocery store (or when they’re just trying to get a breath of fresh air!). We rarely give these engineering feats a second thought, even though they make our lives so convenient. Bridges are such an elegant solution to bodies of water or uneven land that would otherwise be untraversable, and we take them for granted. How many people have ever considered how bridges are made? Fortunately, you’ll learn how if you keep reading.
Although bridge-building details differ based on the body of water the bridge will span, and the type of bridge itself (beam, suspension, truss, arch, etc.), the basis of these bridges is similar. Supports known as piers or piles must be established before the rest of the bridge is created.
To build a bridge over low water, the area may be temporarily filled so that pillars can be erected. Rigs can install pillars deep within a river bed. From there, the bridge can be crafted by using the piers as support, creating platforms, or working from barges, which are less common in low-water situations.
When water is too deep to use the previous method, bridge construction may use the cofferdam method. This alternative uses an enclosure known as a cofferdam, which is made by erecting walls around the area where the bridge will be. Water is continuously pumped out from this area to allow for construction, and 24-hour monitoring is necessary.
The third method of bridge construction, Case Drilling, is more advanced than the previous two. Air pressure created by a watertight chamber allows room for development. Then, a sealed tube is installed in the chamber; engineers can insert and operate a long drill into this tube to direct their efforts efficiently and effectively. The holes created by the drill are filled with casings that will create forms for concrete. Once the concrete forms, it will be used as a stable foundation for the bridge.
In creating suspension bridges, a cable spanning the bridge’s length is strung through the piers and anchored on either side. Hangers connect the chain to the “deck” or surface of the bridge, which is the last part constructed. It takes plenty of resources to streamline transportation infrastructure, but with the power of civil engineering technology and some good old-fashioned construction effort, it’s doable and completely worthwhile!