How a bridge is built over deep water - Suspension Bridge| Amazing Construction

Hello everybody, my name is Losis. Today I'm going to talk about how a giant bridge is built over deep water. In this video, I'm using a suspension bridge as an example. First, let's talk about how it works. Suspension bridge parts consist of towers, anchors, main cable, hangers or suspenders, and bridge decks. When vehicle drives through the deck and puts up a lot of weight, the deck is suspended by the hangers. That is why it's called suspension bridge. The weight then creates tension to the main cables with equal force on both sides. And finally, the weight transfer to the towers. On both sides of the bridge, there are anchors. They hold the main cables in position. Now you can see the weight load being carried by all parts of the bridge. Now you probably wonder how this giant bridge is built. The construction first started with the bridge towers. The underwater part is called a pier. There are three main methods to build underwater piers using pile foundation, cofferdam, and caisson. Pile foundation constructed by drilling down to the riverbed, installing rebars, then pouring concrete. Another method is to use a cofferdam. Cofferdam is built by individual slates, then water is pumped out, creating a water-free and safe space for construction workers. When it is done, the cofferdam will be removed. The next method is using caisson. It is a reinforced concrete box built offsite and then delivered to the location using a submerged vessel. Caisson is sunken down to the riverbed, filled with sand inside. After the underwater piers are built, the construction of the towers begins. At this time, it is no longer underwater, so the construction happens as usual. After the towers are built, it is time to put on the main cables. The main cables look small from the far distance, but it is actually very big in diameter if you look closer. For the reference, you can see here is the size of the Golden Gate Bridge main cable. The main cable consists of so many small steel wires in it. They will be squeezing together to form a big main cable, and then covered by armor plates to prevent weather damages. The whole cable is very big and heavy, so it has to be installed on site by each little wires. This process is called cable spinning. On top of the towers, there are saddles. That's where the cable will be laid on. Workers need to install a travel ropeway and a walking platform. This is a cable carrier. It carries small wires across the top of the towers through the entire bridge. The cable carrier has to make so many trips back and forth to deliver small wires until it is enough to form a big main cable. This process could take months. When the main cable is done, the hangers will be installed. The final part is installation of the decks. Decks are different pieces built off-site then be lifted up using a crane. Decks connect to each other and to the hangers. They must be installed starting from the towers and grow outward on both sides. In this way, make sure to not throw the towers off-balance. That is pretty much a quick way to explain how a giant suspension bridge is built. Thank you for watching this video. If you find this interesting, subscribe to my channel. My name is Lucas and I'll see you in the next video.