Golden Gate Bridge – Suspension Bridge with amazing Story
The concept to make this bridge was conceived in 1920. It is a suspension bridge anchored on the ground. The making of the bridge is although not that simple. Some quick facts :
- 2.7 km is the distance between the two river shores.
- Approx 300 feet depth from the bridge to river surface.
- 27 meter is the width of road on the bridge
- Above Golden gate strait.
- Golden Gate Bridge is one of the most famous landmarks in the world.
- The river channel is between San Francisco bay and Pacific Ocean.
During the growth of San Francisco in 1929 2.5 billion cars were being moved across the strait over a year. The mode of travel was ferries. Thus, a demand of bridge came up during this time.
Bridge faced a lot of difficulties in getting started like
- Golden gate distric was estd. for this work.
- Bridge faced roadblocks from railroad company.
- First the railroad companies of the Sothern pacific who operated the profitable ferries.
- US Department of war also raised concerns over the bridge.
- They feared enemy could bomb the bridge during war to attack navy.
- The city authorities further took the financial work in their hands.
- Bond was issued in secure of the propeties of the citizens of san francisco.
35million US$ was the total cost out of which 5mil US$ was funded by founder of Bank of America. - Eng. Strauss was offered to make the design but city authorirties did not accept.
- Then design input came from Leon Moisseiff, Irving Morrow and Charles Alton Ellis.
The Construction
- In Jan 1933 the construction began
- South tower was far more challenging to erect.
- Seagulls operation was done to make the tower
- 22000 tonnes is the weight of each tower.
- 746 feet or 227 meters above the water
- Entire weight of the bridge is carried by these towers.
- 27572 wires are combined to make the main Cables.
- 2 main cables on the bridge.
- total wires measure 80k miles in length and can circle the earth 3 times.
- first cable was dragged by coastguard and then lifted by crane into 150 tonne curved cable cradles
- bundling and draping strands of wires began
- harsh environment, 45 miles per hour wind
- the main cable is 3 feet wide in dia
- after the main cable smaller 250 pairs of vertical cable hanging were placed
- thermal expansion problem was solved by finger expansion joints.
- 600,000 steel rivets.
- 4 years of construction.
- Opened on 27 may 1937
- 50th anniversary 1987
International orange was the final colour decided to paint the bridge.
Recent Updates
The bridge is very old i.e. more than 80 years. Hence some changes have been done to make it running smooth.
- The bridge is in high risk earthquake zone
- To counter this energy dissipating devices have been subtletly retrofitted and the towers supporting approach ramps have been replaced.
- Bridge is like offshore oil platform
- Suspension ropes have been replaced, light steel road deck placed
The Golden Gate Bridge is a cultural and construction heritage.
