Golden Gate Bridge | The CRAZY Engineering behind it
Summary
TLDRThis video explores the engineering marvel behind the Golden Gate Bridge, focusing on its design and construction. The suspension bridge was chosen for its efficiency in spanning the 2.7 km distance without obstructing ship traffic, unlike beam or arch bridges. The video discusses key challenges, such as balancing cable tension, constructing stable foundations in the Pacific Ocean, and addressing thermal expansion. It highlights innovations by chief engineer Joseph Strauss, including cable systems, tower designs, and safety measures, emphasizing the bridge's resilience even under extreme conditions.
Takeaways
- π The Golden Gate Bridge is a suspension bridge that spans 2.7 km over the Pacific Ocean, using a parabolic cable system for support.
- β οΈ Without the suspension cable system, the bridge would fail due to the lack of structural support.
- ποΈ Joseph Strauss, the chief engineer, chose a suspension design because beam and arch bridge designs were either impractical or costly for this location.
- π Suspension bridges rely on tall towers and cables anchored to the ground to balance tensile forces, preventing the towers from bending inward.
- π§ Strauss solved the issue of concrete cracking by connecting the suspension cables to a steel structure, which provided a strong and flexible connection.
- π οΈ The bridge deck was divided into seven sections with finger expansion joints to allow for thermal expansion, preventing damage from temperature changes.
- ποΈ Constructing the south tower foundation was challenging due to its location in the deep and turbulent waters of the Pacific Ocean.
- π Taller towers in suspension bridges reduce tension on cables and increase bridge strength, which was key in the design of the Golden Gate Bridge.
- π© The main cables were created by spinning 27,000 smaller wires, resulting in a total steel wire length of 129,000 km.
- π On the bridge's 50th anniversary, it successfully supported a massive crowd of 300,000 people, sagging by 2 meters but remaining structurally sound.
Q & A
What would happen to the Golden Gate Bridge if its suspension cable system was not present?
-Without the suspension cable system, the bridge would collapse, as the cables provide crucial support to the road deck, distributing the weight and ensuring the bridgeβs stability.
Why was the suspension bridge design chosen for the Golden Gate Bridge?
-The suspension bridge design was chosen because it allows ships to pass underneath and avoids the need for costly underwater piers in deep water, making it an efficient solution for the 2.7 km distance between the coastlines.
How did the engineers resolve the issue of inward bending of the towers caused by the tension in the main cables?
-The engineers resolved the issue by extending the main cable and anchoring it to the ground via an anchorage system. This balanced the horizontal forces acting on the towers.
Why did Mr. Joseph Strauss move the towers closer together, and how did this impact the cable design?
-By moving the towers closer together, the length of the unsupported bridge deck was reduced, lowering the tension in the cables. This allowed for a reduction in the cable's cross-section area, optimizing costs.
How did Mr. Strauss address the issue of the suspension cables causing cracks in the concrete deck?
-Mr. Strauss addressed this by connecting the steel suspenders to a steel structure beneath the road deck, as steel-to-steel connections are stronger and prevent the formation of cracks in the brittle concrete.
What solution did the engineers use to handle thermal expansion in the Golden Gate Bridge?
-The engineers used finger expansion joints between the road deck sections to allow movement during temperature changes. These joints prevent stress on the towers and road deck caused by expansion and contraction.
Why is the height of the towers crucial in a suspension bridge design?
-The height of the towers is crucial because taller towers reduce the tension in the cables by increasing the angle of the cables. This reduces the overall stress on the structure, making the bridge stronger.
How was the south tower foundation constructed, and what challenges did the engineers face?
-The south tower foundation was built on bedrock 50 feet below the seabed. Engineers faced challenges from the violent Pacific Ocean currents. To overcome this, they built protective fender walls and an RCC slab to safely carry out the construction beneath the water.
How was the main cable of the Golden Gate Bridge constructed?
-The main cable was constructed by spinning 27,000 smaller steel wires over the towers and clamping them together. The wires were pressed using a hydraulic press and then bound into a single large cable.
What happened to the Golden Gate Bridge during its 50th anniversary celebration when it was overloaded with people?
-During the 50th anniversary, the Golden Gate Bridge sagged by almost 2 meters due to the weight of over 300,000 people, but the suspension system held strong and prevented any structural failure.
Outlines
π Introduction to the Golden Gate Bridge's Engineering
This paragraph introduces the Golden Gate Bridge and its key structural component: the suspension cable system. It outlines how the bridge's construction involved overcoming the powerful currents of the Pacific Ocean with the help of Chief Engineer Joseph Strauss. The paragraph explains why a suspension bridge design was chosen over other designs, such as beam and arch bridges. It highlights the suspension bridge's basic design, consisting of two towers with a main cable suspended between them. Additionally, it touches on some of the challenges engineers faced, including how the tension in the main cable affects the towers and how the bridge deck is supported. The choice of suspension design was critical due to the large span and deep waters, making alternative designs costly and impractical.
π§ Construction and Safety Measures of the Golden Gate Bridge
This section details the construction process of the bridge, emphasizing the importance of safety measures taken to protect workers. It describes how prefabricated components were brought to the site and assembled using derricks and rivets. A net was installed beneath the bridge deck to catch any falling workers. Suspension cables were then connected to the main cable to evenly distribute the load. The construction process involved painting the bridge with a special International Orange color for protection. The paragraph also describes the concrete road deck's construction, where wooden formwork and steel bars were used before pouring concrete. Finally, the section addresses the thermal expansion challenge and how Mr. Strauss used finger expansion joints to prevent damage from temperature changes, dividing the deck into separate sections to account for differential expansion between steel and concrete.
π Overcoming Challenges in Building the South Tower
This part focuses on the challenges faced while constructing the South Tower, which was built in the turbulent waters of the Pacific Ocean. The foundation required digging down to the bedrock, 50 feet below the seabed, with divers performing underwater blasts to clear debris. The structure's cross-section reveals the construction of fender walls, which had to withstand inward oceanic forces. The workers built a thick reinforced concrete slab to support these walls, allowing them to dig safely underneath it. Once the foundation was complete, the assembly of the towers began using hollow steel cells, carefully planned to give the tower its final shape. The paragraph also explains how the main cables were constructed from 27,000 smaller wires. A catwalk bridge was created for workers to lay down the wires, which were wound together using galvanized steel wire, giving the cable its large pipe-like appearance. The construction of the deck and road was completed afterward.
π The Golden Gate Bridge: Strength, Resilience, and Legacy
This concluding section recounts the Golden Gate Bridge's strength and resilience, particularly on its 50th anniversary when it supported an immense crowd, causing the road deck to sag by 2 meters. Despite the extreme load, the bridge held strong, showcasing the robust design engineered by Mr. Strauss 89 years ago. The paragraph acknowledges the technological marvel of the bridge and its significance in civil engineering history. It also invites viewers to join the team behind the video, thanking them for their time and highlighting the incredible feats achieved during the bridge's construction.
Mindmap
Keywords
π‘Suspension Bridge
π‘Cable System
π‘Towers
π‘Anchorage System
π‘Thermal Expansion
π‘Concrete Road Deck
π‘Suspension Cables
π‘International Orange
π‘Finger Expansion Joints
π‘Tensile Load
π‘Optimal Tower Height
Highlights
The Golden Gate Bridge's suspension cable system is crucial for its stability, without it, the bridge would fail.
A simplified suspension bridge is constructed by erecting two towers and suspending a cable in a parabolic shape between them.
The Golden Gate Bridge is a suspension bridge designed to allow for ship passage and to overcome the challenges of the site's geography.
Conventional beam bridges would block ship movement and are costly to construct at such depths, making them unsuitable for the site.
Arch bridges would require an extremely high structure to maintain their shape, leading to complexity and high construction costs.
Suspension bridges offer an efficient solution to the site's challenges, balancing cost and functionality.
The main issue with the initial suspension bridge design is the inward bending of towers due to the horizontal force from the main cable.
Extending the main cable and anchoring it to the ground via an anchorage system can resolve the horizontal force issue on the towers.
Optimizing the bridge's design by moving the towers closer together reduces the unsupported bridge deck length and the cable's tension.
The width of the main cables on the Golden Gate Bridge is more than half the height of an average human.
Directly connecting steel suspenders to a concrete deck can lead to cracks due to the brittle nature of concrete.
Mr. Strauss solved the connection issue by using a steel structure to connect the suspenders, ensuring a strong steel-to-steel connection.
The road deck's width was kept at 27 meters to accommodate current and future traffic demands.
Construction of the bridge was challenging due to foggy and windy conditions, requiring prefabrication of members and assembly on-site.
A net was installed under the bridge deck to ensure the safety of laborers during construction.
To maintain equal loading on the cable, the assembly system had to be assembled simultaneously and equally in two directions for each tower.
The bridge was painted International Orange, a special color chosen for its visibility and aesthetic appeal.
Thermal expansion is a significant engineering challenge addressed by dividing the deck into separate pieces with finger expansion joints.
Mr. Strauss designed the optimal tower height of 746 ft to balance strength and construction cost.
The construction of the south tower was particularly challenging due to the violent Pacific Ocean currents.
Divers were hired to blast the seabed and clear debris for the construction of the south tower's foundation.
A thick reinforced concrete slab was constructed to protect workers from ocean currents while digging for the hard strata.
The main cables of the bridge are composed of 27,000 smaller wires, totaling 129,000 km of steel wire.
The bridge's construction was a testament to the engineering advancements of the time, showcasing innovative solutions to complex problems.
On its 50th anniversary, the Golden Gate Bridge withstood an extreme load of over 300,000 people without collapsing, demonstrating its resilience.
Transcripts
when observing the Golden Gate Bridge
floating over the Pacific Ocean your
eyes may be drawn to its beautiful
suspension cable system what would
happen to the bridge if this cable
system was not
present in short it would be a
catastrophe let's Brave the deadly
currents of the Pacific Ocean and
construct the Golden Gate Bridge with
its Chief design engineer Mr Joseph
Strauss we'll also explore the
mesmerizing engineering Feats the Golden
Gate Bridge has achieved come
along the Golden Gate Bridge is a
suspension bridge a highly simplified
suspension bridge can be constructed the
following
way 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
attach a concrete road Deck with
pillars this C clearly provides support
to 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 so the road deck won't
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
coastlines of the Golden Gate is a
whopping 2.7 km let's construct a
conventional beam bridge
here you can see that the road deck is
supported by various
peers the presence of these peers blocks
the movement of ships
underneath as you can imagine
constructing them 300 ft deep in the
water would be extremely costly thus the
beam design does not make sense
here now let's consider an arch bridge
this would definitely provide
passageways for
ships however to maintain the arch shape
the bridge would need to be extremely
high such a structure would be quite
complex to
construct that's 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 design details of the
suspension
bridge this design has one glaring issue
if you construct the bridge like this
the towers will bend inward as
shown the main cable is under a huge
tensile load this applies force on the
tower when you resolve this Force you
can see that there is an imbalanced
horizontal force acting inward on the
tower which explains why the towers
Bend can you find a solution for this
issue to cancel this horizontal Force we
need the same force acting in the
opposite direction the straightforward
solution is to extend the main cable and
anchor it down to the ground via an
Anchorage
system however we can optimize the
financial resources needed to construct
this bridge with a simple
idea all we need to do is move the
towers closer to one
another now the length of the
unsupported bridge deck is reduced
due to this tension in the cable will be
reduced this will obviously lead to a
cable with less cross-section area the
width of the main cables are more than
half the height of the average human as
a tourist attraction a piece of this
impressive main cable is demonstrated
near the Golden Gate
Bridge however if you construct the
bridge with this exact design it will
experience a premature death can you
guess why this would be the
case connections are the weakest part in
any structural system the direct
connection of the steel suspenders with
the concrete deck will lead to the
formation of cracks on the deck since
concrete is brittle in
nature let's see how Mr Strauss solved
this
problem Mr Strauss decided to connect
the suspenders to a steel structure
steel to Steel connection is always
strong the details of the connection
between the suspenders and steel
structure are Illustrated
here the road deck is placed on this
structure Mr Strauss kept the width of
the road to 27 M to account for current
and future traffic
demands assembling the structure like
this was far from an easy task due to
foggy and windy conditions at the site
to facilitate the process workers
prefabricated each member of the trust
and brought them to the site VI
ships assembly of the individual members
was accomplished using a Derek and their
connections were secured via
rivets to ensure the safety of the
laborers a net was installed underneath
the bridge deck as the construction of
the bridge progressed they
simultaneously connected the structure
with the main cable using suspension
cables moreover to maintain equal
loading on the cable workers had to
assemble this system simultaneously and
equally in two directions for each Tower
thus the Golden Gate was
bridged 250 pairs of vertical cable were
used and they hung the whole bridge deck
to the main cable after the construction
of the steel structures the workers
painted the bridge a special
International Orange
color next let's examine some details of
concrete road construction on top of
this solid
structure workers first laid down wooden
form
workor they attached steel bars welded
them to the steel sections below
them and later poured and compacted the
concrete using a needle
vibrator our Bridge looks perfect now
but is it ready to support vehicle
movement not yet we must first tackle
another major engineering challenge
thermal
expansion the concrete and Associated
Steel structure will expand or contract
based on environmental temperature
variations if we had constructed 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 on the
road eventually the bridge would
experience
damage if you have ever visited the
Golden Gate Bridge you may have noticed
peculiar connections on the
road these connection
called finger Expansion Joints were Mr
strauss's solution to solve the thermal
expansion
problem Mr Strauss divided the deck into
seven separate pieces you can see this
bridge has three cradles the finger
Expansion Joints are installed between
the gaps during an extreme temperature
increase the length of the road deck
increases and these joints move by
almost
4T what an elegant solution for a
serious issue however there is still a
small problem to solve the thermal
expansion of the steel is slightly
higher than that of the
concrete this differential expansion can
cause trouble for the concrete deck
which is composed of a mixture of
concrete and steel bars but this
expansion issue is negligible when the
length is small this is why the Golden
Gate contains tiny Expansion Joints
every 50
ft another great design challenge Mr
Strauss dealt with was the height of the
tower Let's do an experiment to gain a
better
understanding I had two Bridge designs
with me a toll Tower design it is having
a high sack and the next one a short
over design obviously a small
sag the question is that which design
gives more strength to a suspens kind of
bridge Let's test the first design using
a road dech that to a really heavy Road
deck
when I attach the road deck this design
is standing strong this design is
safe now let's attach the same weight to
the next design to the short to
design this bridge went for a sudden
failure I couldn't react to that so in
short we proved experimentally the toll
to design is the best for a suspens kind
of bridge is more strong the question is
why to get answer for this let's invite
the chief engineer of this whole project
Mr Joseph St to the video the major
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 since the small Tower design
has a low angle to balance the weight
the cable has to induce more
tension this is why the short Tower
fails during the experiment the tall
tower will obviously reduce the tension
in the cable but it will cost much more
to construct it that's precisely why Mr
Strauss calculated the optimal tower
height of 746 ft a happy average between
these two
scenarios now let's get into the most
exciting part of this video construction
of the Golden Gate Bridge in a hostile
environment first we start with the
tower const construction did you know
the construction of the Southside Tower
was tougher than the North Tower this is
because the south tower construction had
to overcome the violent Pacific Ocean a
tower Foundation must be constructed on
strong Bedrock called hard strata for
the South Side the hard strata was 50 ft
below the seabed level and had a steep
floor we need to dig this deep and build
an RCC foundation for the South
Tower to do so first professional divers
were hired to blast bombs underwater the
divers cleared the debris of the
explosion and made a better
surface now it's time to construct a
steel and wooden framework on this
surface the divers obviously did an
amazing job
here now let's see the cross-section of
the structure they built then the
concrete was poured to create something
called Fender walls afterwards all the
inside water was pumped out
now that the fender wall is ready can
the workers go inside and start digging
for the hard
strata here is the issue the ocean
currents are so nasty that the fender
wall will have to bear a huge inward
force and can collapse this kind of
construction is highly
unsafe Mr Strauss had a clever idea
initially they placed the blasting tubes
the workers shaft and the material shaft
inside the fender walls the trick was to
construct a thick reinforced concrete
slab so that workers can work beneath it
the way workers reached the workers
chamber was quite interesting it was via
the workers shaft they continuously
drilled The Boulders and dug underneath
the RCC
slab this RCC slab supported the fender
walls and protected the workers
underneath against deadly
currents during this process the entire
fender wall structure was allowed to
sink
slowly you can see its knife-like
shape eventually they reached the rocky
hard
strata after leveling the hard strata
they made a steel structure there and
built an RCC
Foundation the construction of the
complete Foundation is quite easy now
you can see how the fender walls protect
the main Foundation from the deadly
waves now it's to see the construction
of the gigantic
Towers once the foundation was ready
they assembled the steel base plate on
it now comes the magic of these hollow
steel cells they assembled and riveted
these cells as if they were constructing
a tower using Legos you can see how
cleverly they had to plan the shapes and
sizes of these cells so that the tower
would finally achieve the shape which it
was intended to
achieve Mr Strauss designed this unique
cellular structure to be economical as
well as
strong the tower construction was then
complete next it was time to lay down
the main cables for this they first
installed cable Saddles at top the
towers you may think that the main cable
is a single solid cable the main cable
is in fact made up of
27,000 smaller wires and a total length
of
129,000 KM length of Steel wire was
consumed for fabrication of it to start
laying these cables workers first
constructed a catwalk bridge for
themselves at first workers laid a
support
wire the main cables made their Journey
via these spinning
wheels furthermore these small wires
were passed over the tower through the
cable saddle one by one and were then
clamped by
laborers then the work pressed the wires
tightly using a hydraulic
press they simultaneously wound the
wires together using galvanized steel
wire which is why the main cable looks
like a single large
pipe these cables are anchored to the
Bedrock with strand shoe steel
plates after laying the main cables the
suspension cables were attached to it
all that was left to do was construct
the deck structure and lay down con for
the road you already know how they did
that a strange incident happened on the
Golden Gate Bridge on its 50th
Anniversary when more than 300,000
people gathered on the bridge all at
once you can probably predict what will
happen if a suspension bridge is
overloaded overloading a suspension
bridge can cause it to
Sag this can even cause the main Towers
to bend inward this is exactly what
happened on that day the road deck
sagged by almost two 2 m 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 signified a leap
in civil
engineering before you leave don't
forget to become a lesic team member we
hope you enjoyed the video thank you for
watching
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