What Type of Bridge is the Golden Gate Bridge

If you ever wondered, "What type of bridge is the Golden Gate Bridge?" -- the answer is found in its cables. The vertical cables you see spanning the length of the bridge "suspend" the deck below them, thus revealing the answer. The Golden Gate Bridge is a suspension bridge.

Perhaps the world's most famous suspension bridge.

Admired around the world, San Francisco's Golden Gate Bridge is a perfect example of a suspension bridge, one of six main types of bridges. The other types are:

• Beam bridges
• Cantilever bridges
• Arch bridges
• Truss bridges
• Cable-stayed bridges

Suspension bridges are among the most beautiful bridges in the world, representing a symmetry that directly reflects its internal balance. The Golden Gate Bridge, completed in 1937, remains an engineering marvel the world over.

Though cable-stayed bridges and suspension bridges look quite similar, they are different in how their cables are attached and thus, how their construction bears the weight. With cable-stayed bridges, all cables are attached to the tower(s), which in turn, bears the load. With suspension bridges, you have main cables running between the two anchorages and suspender cables spanning the length of the bridge. All cables are under constant tension.

However, because the cables run the length of the bridge, weight travels. It's transmitted to the towers, as well as to the anchorages on each side. Through this setup, weight is evenly distributed before being deposited into the ground (by way of the towers and anchorages). In addition, suspension bridges benefit from a deck truss, found beneath the bridge deck. This support helps further stabilize the structure, minimizing any motion that might affect the bridge’s delicate balance.

Next time someone asks, "What type of bridge is the Golden Gate Bridge?" -- simply point to the cables: the stretched cables and suspender cables. Indeed they are the key, and as noted, they're built to absorb tension forces. The main cables that pass over the towers? They are literally stretched.

The Golden Gate Bridge has two main cables that rest above its 746-foot tall towers and end in a curve at its two opposing anchorages. From the main cables, 250 pairs of suspender cables are inserted. These cables suspend the Bridge's roadway and help any/all weight travel evenly across the bridge. Because the suspender cables are spaced out, no one cable is under enough stress to snap free.

Golden Gate Bridge main cable stats:

• Diameter of each cable: 36 3/8 inches
• Length of each cable: 7,650 feet long
• Composition of each cable: 27,572 galvanized wires, bundled into 61 strands of 454 wires each
• Combined total weight: Of each cable, plus vertical suspenders and accessories, is 24,500 tons

The cables, towers, anchorages, deck and deck truss all work in concert on a suspension bridge. If any one part is compromised, the entire structure fails. Did you know that the construction of a suspension bridge is such that it can span the longest distance of any bridge type? As far as bridge length is concerned, the order goes:

1. Suspension bridge
2. Cable-stayed bridge
3. Cantilever bridge

Suspension bridges can span distances 2,000 to 7,000 feet, and back in 1937, the Golden Gate Bridge pushed towards the high end of that extreme. Besides that, its boldness in design and color has made it a global inspiration.

Upon its completion, the Golden Gate Bridge had the tallest towers and the longest span in existence. Though these records have fallen in the intervening years, what remains is the fact that the Golden Gate Bridge is a miraculous engineering achievement -- for 1937 and today. It measures 6,450 feet in length, with a main bridge span of 4,200 feet. Its side spans measure 1,125 feet each. To cross the bridge entirely, including its approaches, you'll travel some 1.7 miles before you're done. Its two towers rocket 746 feet into the sky and its two anchorages combine for 60,000 tons. The width of the bridge is 90 feet and the clearance from the San Francisco Bay below, 220 feet.

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