The longest plan to rebuild cable-stayed bridges in the world after 80 years

The construction of lighter bridges allows the abutments to be built closer to the shore, where the riverbed is more shallow, which will significantly reduce costs.

Since being opened on May 27, 1937, Golden Gate Bridge has become one of the most prominent symbols of the United States.

In 1870, it was recognized the need to build a bridge across the Golden Gate Strait to connect the city of San Francisco to Marin County. However, it was not until half a century after engineer Joseph Strauss submitted to his design.

Through the steps and finally the project was approved, the suspension bridge took four years to build. When completed, the Golden Gate Bridge becomes the longest suspension bridge in the world with cables that hold the bridge's lane without needing intermediate pillars.

When completed 80 years ago, the Golden Gate Bridge is the longest cable-stayed bridge in the world.(Photo: somchaij).

The total cost to build the bridge at that time was about $ 37 million, equivalent to a billion dollars at today's exchange rate. But if the bridge was built today and not 80 years ago, what would it be like?

The first suspension bridges in the world simply connect the two cliffs with flexible ropes across the valley or a river. Hundreds of years ago, hanging wires were taken from plants. The Brooklyn Bridge in New York City opened in 1883, being the first suspension bridge to use steel cables and became the standard for later suspension bridges.

The Golden Gate bridge cables are the only thing that has never changed since 1937 until now. Each main cable is made up of 27,572 small steel fibers with a pencil-like thickness. In total there are about 128,800km of steel wire to connect from one end of the bridge to the other.

Explaining why a lot of small cables are needed to make a giant cable, engineers say this will increase the rigidity of the cable, if one strand has a problem, the demand will still No problems. Or even if there is a sabotage, tens of thousands of small steel wires will gradually break down, helping people on the bridge have time to evacuate in time.

Since the bridge construction project in San Francisco Bay, there is a lot of concern about the bridge structure that can withstand strong winds, turbulent waters and unexpected earthquakes. San Francisco is located at the intersection of two tectonic plates, apparently no one wants to see an earthquake that could collapse the bridge to receive 112,000 cars a day.

The Golden Gate bridge cables are the only thing that has never changed since 1937 until now.

To avoid this problem, construction engineers also put shock absorbers on each side of the bridge to absorb the energy from the earthquake caused by the earthquake. These special vibration dampers are designed from several-meter diameter cylinders with lead cores and rubber ends, which can effectively absorb the impact force that can cause a bridge collapse.

During the past 80 years, to keep the Golden Gate Bridge always in its original state, the maintenance team must constantly repair and maintain the bridge in every day, ensuring that no parts are corroded or damaged. . This work must be done very accurately.

There are other problems when maintaining the structure. As time passes and the temperature changes in the air, the cable is always stretched or shrunk. Adjusting the wire length as it is is an extremely difficult task and must be done continuously.

So what if we rebuild the bridge today? Due to the large maintenance cost, there have been some suggestions that the Golden Gate Bridge should be rebuilt. Ignoring the political factors, how will today's engineers rebuild from the top of this iconic bridge?

Over time, researchers have developed more lighter materials. Using cables made of polymers rather than concrete or steel is a way to reduce the weight of this project. A large weight affects 70% of the bridge's stamina, which is the maximum load it can withstand before it collapses. By reducing volume, construction and maintenance costs will be lower.

For example, designers began using FRP in bridges like the Market Bridge in western Virginia. FRP uses plastic to combine with fiberglass or carbon fiber to create the strength of the fiber, and uses 4 times lighter concrete than conventional concrete.

We have at least a few dozen years to contemplate this architectural masterpiece.

Perhaps the first thing to do when designing and rebuilding the bridge changes the cable part. Because steel has corrosion properties over time and is very heavy, it is necessary to change them because carbon is not corroded, light and widely used in the world.

In addition to the structure of the bridge, other elements of the bridge can also be replaced with lighter materials. For example, roads, using plastic composite wood can make the bridge's surface lighter 5 times. The first cable-stayed bridge using the CFRP suspension cable was Switzerland's Stock Bridge, opened in 1996.

The construction of lighter bridges allows the abutments to be built closer to the shore, where the riverbed is more shallow, which will significantly reduce costs. The towers of the current Golden Gate Bridge are built in deep water with swirling currents, which are very difficult to construct.

Anyway, the Golden Gate Bridge is now a symbol of design and construction, the bridge is still under careful scrutiny to ensure it does not exceed the load. We have at least a few dozen years to contemplate this architectural masterpiece.