... like I'm 5 years old
Suspension bridges are a marvel of engineering that we often see in our daily lives. Imagine you have a rope between two trees and you put a plank of wood on top of it to cross a muddy puddle. The trees are like the tall towers of the bridge, the rope is like the main cables, and the plank of wood is the roadway you drive on. The main cables hang in a curve between the towers and are anchored firmly at each end. The roadway hangs from smaller ropes (suspenders) connected to the main cables. Just like how the plank can carry your weight across the puddle, the roadway of a suspension bridge can carry the weight of cars, buses, and even trains across large bodies of water or valleys.
Think of a suspension bridge like a hammock. The hammock's fabric is the roadway and the ropes at each end that you tie to trees are like the main cables. The trees are the bridge's towers. Just like you can lie on the hammock and it supports your weight, a suspension bridge can support the weight of heavy vehicles.
... like I'm in College
Taking a closer look, suspension bridges are meticulously designed structures. The tall towers are rooted deep into the ground and act as vertical supports. The main cables, which are made from thousands of individual steel wires, stretch from one anchor, over the towers, to the other anchor. They shape a curve called a catenary curve, which distributes the load of the bridge and its traffic efficiently. The smaller vertical cables, or suspenders, connect the main cables to the roadway. As vehicles drive over the bridge, the weight is transferred from the roadway, through the suspenders and main cables, to the towers and finally to the ground. This distribution of weight is what allows the bridge to withstand heavy loads and forces that act on it.
To illustrate how a suspension bridge works, let's use LEGO bricks. The LEGO towers are built on a firm base, representing the towers anchored to the ground. A flexible LEGO string represents the main cables, looping over the towers and secured at each end. Smaller LEGO strings are hung from the main string, and a flat LEGO piece is attached to these to represent the roadway. The weight of the LEGO cars on the roadway is transferred through the smaller strings to the main string, then to the towers, and finally to the base. This LEGO setup demonstrates how a real suspension bridge functions, showing the distribution of weight and the role of each component.
... like I'm an expert
In engineering terms, suspension bridges are an optimal solution for spanning long distances due to their load distribution and flexibility. The towers act as cantilevers, balancing the forces acting on them. The main cables follow a parabolic trajectory, not truly a catenary, due to the uniform load along the cable. The load from the deck is transferred to the cables via suspenders, which in turn distribute the load to the towers and anchorages, utilizing the immense tensile strength of steel. This efficient distribution of compressive and tensile forces allows suspension bridges to span distances of up to 2km. Moreover, they can withstand wind forces due to their inherent flexibility, a feature accomplished by allowing the deck to move laterally and torsionally.