Golden Gate Bridge | The CRAZY Engineering behind it

When watching the Golden Gate Bridge floating above the Pacific Ocean, your eyes may be drawn to its beautiful suspension cable system. What would happen to the

bridge

if this cable system were not present? In short, it would be a catastrophe. Let's face the deadly currents of the Pacific. ocean and we will build the

golden

gate

bridge

with its chief design engineer, mister joseph strauss, we will also explore the fascinating

engineering

feats that the

golden

gate

bridge has achieved. come along the golden gate bridge is a suspension bridge a highly simplified suspension bridge can be built as follows In this way, we erect two towers at both ends of the ocean and suspend a long cable between the towers.

This cable can be approximated as a parabola. Now let's connect a concrete deck with pillars, this clearly provides support at the end of the road deck when we connect the suspension cables between the main cable and the road deck, the bridge is also supported along its length to that the road deck does not fail, as we saw earlier, this is the basic design behind the suspension bridge before exploring more about the Golden Gate Bridge, let's first understand why the engineers chose a suspension design for this site the distance between the two shores of the golden gate is a whopping 2.7 kilometers let's build a conventional girder bridge here you can see that the road deck is supported by several pillars the presence of these pillar blocks the movement of the ships underneath, as you can Imagine, building them 300 feet deep in water would be extremely expensive, so the beam design doesn't make sense here.

Now let's consider an arch bridge, this would definitely provide passageways for ships, however to maintain the shape of the arch. The bridge would have to be extremely high, such a structure would be quite complex to build, that is why Mr. Joseph Strauss opted for a suspension design, a bridge that could overcome all the drawbacks we discussed in a very efficient way. Now let's get into the details of the suspension bridge design this design has an obvious problem if you build the bridge this way the towers will bend inwards as shown the main cable is under a huge tensile load this applies force on the tower when you solve This force you can see that there is an imbalance horizontal force acting inwards on the tower, which explains why the towers bend.

Can you find a solution for this problem to cancel this horizontal force? We need the same force acting in the opposite direction. The simple solution is to extend the main cable and anchor it down. the ground through an anchoring system, however, we can optimize the financial resources needed to build this bridge with a simple idea, all we need to do is move the towers closer to each other now the length of the unsupported bridge deck will be reduces because this tension in the cable will be reduced, this will obviously lead to a cable with less cross-sectional area.

The width of the main cables is more than half the height of the average human being. As a tourist attraction, a piece of this impressive main cable is displayed near the gold. Gate Bridge, however, if you build the bridge with this exact design, you will experience an early death. Can you guess why that would be so? Connections are the weakest part of any structural system. Directly connecting the steel stays to the concrete deck will lead to the formation of cracks in the deck as concrete is brittle by nature. Let's see how Mr. Strauss solved this problem.

Mr. Strauss decided to connect the stays to a steel structure. The steel to steel connection is always strong The details of the connection between the stays and the steel structure are illustrated here The road deck is placed on this structure Mr Strauss kept the width of the road at 27 meters to take into account Taking into account current and future traffic demands, assembling the structure in this way was not an easy task due to the foggy and windy conditions at the site. To facilitate the process, workers prefabricated each member of the truss and brought them to the site through of ships.

The assembly of the individual members was carried out using a derrick and their connections were secured by rivets to ensure the safety of the workers, a net was installed under the bridge. deck as the construction of the bridge progressed, they simultaneously connected the structure with the main cable using suspension cables, in addition, to maintain the same load on the cable, the workers had to assemble this system simultaneously and equally in two directions for each tower , so the golden gate was bridged 250 Pairs of vertical cables were used and the entire bridge platform was hung to the main cable.

After the construction of the steel structures, workers painted the bridge with a special international orange color. Next, let's examine some details of the construction of the concrete road on this solid structure. They first placed a wooden formwork, placed steel bars, welded them to the steel sections beneath them, and then poured and compacted the concrete using a needle vibrator. Our bridge looks perfect now, but is it ready to support the movement of vehicles? Not yet, we must first address another important one.

engineering

challenge thermal expansion the concrete and associated steel structure will expand or contract depending on ambient temperature variations if we had built this bridge as a single piece during a hot sunny day the bridge would expand and cause tremendous stress on the tower, as well as eventually the bridge would be damaged if you have ever visited the golden gate bridge you may have noticed peculiar connections along the way these connections called finger type expansion joints were mr strauss' solution to solve the expansion problem thermal mr strauss divided the deck into seven separate pieces You can see that this bridge has three supports, finger type expansion joints are installed between the spaces during an extreme rise in temperature, the length of the road deck increases and these joints They move almost 4 feet, what an elegant solution to a serious problem, however, there is still a small problem to solve: the thermal expansion of steel is slightly greater than that of concrete.

This differential expansion can cause problems to the concrete deck which is composed of a mixture of concrete and steel bars, but this expansion problem is negligible when the length is small. That's why the Golden Gate contains small expansion joints every 50 feet. Another major design challenge Mr. Strauss faced was the height of the tower. Let's do an experiment to understand better. He had two bridge designs with me. One tall tower design is having a high sag and the next a short run design obviously a small sag the question is which design gives more strength to a type of suspension bridge.

Let's try the first design using a road label that shows a really heavy rod deck when I put the rod deck on this design is staying strong this design is safe now let's tackle the same weight for the next design for the short hour design this bridge suffered a sudden failure i couldn't react to that so in short we experimentally produced the high tower design is the best for a type of suspension bridge it is stronger the question is why to get an answer to this let's invite mr joseph strauss from the project from the chief engineers room to the video the main difference between these two designs is the angle of the cable in both The load to be carried is the same.

The vertical component of the cable tension balances this weight as the small tower design has a low angle to balance the weight. The cable has to induce more tension. This is the reason why the short tower fails during the experiment. The tall tower. It will obviously reduce the strain on the cable but will cost much more to build, which is precisely why Mr. Strauss calculated the optimal height of the tower to be 746 feet, a happy average between these two scenarios. Now let's get into the most exciting part of this Golden Gate Bridge construction video in a hostile environment.

First we start with the construction of the tower. Did you know that the construction of the tower on the south side was harder than the north tower? This is because the construction of the south tower had to overcome the violent Pacific Ocean. The foundation of the tower must be built. built on strong bedrock called hard strata for the south side, the hard strata was 50 feet below the seabed level and had a steep floor, we need to dig that deep and build a rcc foundation for the south tower to do it , first professional divers were hired for underwater explosive bombs the divers cleaned the debris from the explosion and made a better surface now it's time to build a steel and wood frame on this surface the divers obviously did an amazing job here now let's see the cross section of the structure they built then Concrete was poured to create something called defense walls, then all the water inside was pumped out Now that the defense wall is ready, can the workers go in and start digging for the hard strata?

Here's the problem, the ocean currents are so nasty that the defense wall will have to withstand a huge inward force and may collapse. This type of construction is very unsafe. Mr. Strauss had a clever idea. Initially they placed the blast tubes, the workers' pit and the material pit within the walls of the defences. The trick was to build thick reinforced concrete. slab so that the workers can work under it the way the workers reach the workers chamber was quite interesting, it was through the workers well who continuously drilled the rocks and dug under the rcc slab.

This slab of rcc supported the walls of the defenses and protected the workers below against deadly drafts. During this process, the entire fender wall structure was allowed to slowly sink. You can see its knife shape. Finally they reached the hard, rocky strata. After leveling the hard strata, they made a steel structure there and built a rcc foundation. Base construction complete. It's quite easy, now you can see how the defense walls protect the main foundation from the deadly waves. Now it's time to see the construction of the giant towers. Once the foundation was ready, they assembled the steel base plate, now comes the magic of these holes. steel cells assembled and riveted these cells as if they were building a tower using legos.

You can see how cleverly they had to plan the shapes and sizes of these cells so that the tower finally reached the shape it was intended to achieve, Mr. Strauss. He designed this unique cellular structure to be economical and strong. Then the construction of the tower was completed. Then it was time to run the main cables. To do this, they first installed cable supports on top of the towers. The main cable can be thought of as a single solid cable. In fact, the main cable is made up of 27,000 smaller wires and a total length of 129,000 kilometers of steel wire was consumed for its manufacture.

To start laying these cables, the workers first built a walkway bridge for themselves, at first the workers placed a support. The main cables made their journey through these rotating wheels, furthermore, these small cables passed over the tower through the cable chair one by one and then were clamped by the workers, then the workers pressed the cables firmly using a press. hydraulics and simultaneously wound the cables. Using galvanized steel wire, that's why the main cable looks like a single big tube. These cables are anchored to the bedrock with steel shoe plates. After the main cables were laid, the suspension cables were attached.

All that was left to do was build the platform. structure and lay concrete for the road you know how they did it that a strange incident occurred on the Golden Gate Bridge on its 50th anniversary when more than 300,000 people gathered on the bridge at once, you can probably predict what will happen if a The suspension bridge is overloaded Overloading a suspension bridge can cause it to sink This can even cause the main towers to bend inward This is exactly what happened that day The road deck sank almost two meters even with this extreme load Mr. Strauss's incredible suspension bridge stood strong, one can only admire the technologies they developed 89 years ago in the design and construction of the Golden Gate Bridge.

This successful project represented a leap in civil engineering. Before you go, don't forget to become a memberfrom the lessex team. We hope you enjoyed the video. Thanks for watching