Transportation Success: Forth Bridge, Scotland
Location: The Forth Bridge stretches from South Queensferry to North Queensferry in Scotland. This area received a lot of ferry traffic and the increase in railway transportation in the late 1800s emphasized a need for a bridge at this location.
When: Construction of the Forth Bridge began in 1883 and it was opened for operation in 1890.
Type of bridge: Cantilever
The Forth Bridge consists of three cantilever structures situated on granite platforms. Cantilevers are supported on one side and carry a load on the other.
Significant attributes: The Forth Bridge is regarded as the first 100% steel bridge in Britain. Additionally, the Forth Bridge was an attempt to achieve a successful transportation system in the area after the collapse of the Tay Bridge in 1879.
Dimensions: Height: cantilevers are 100 m (110m above surface of water at high tide)
Weight: 53,000 tons
Length: 2.5 km (521 m cantilever spans)
Cost: About 3 million pounds
Awards: At the time of construction, the spans of the individual cantilevers (521 m) were the longest and second longest in the world and remained so for 28 years. The Forth Bridge is still the longest cantilever bridge in the world. The Forth Bridge is protected as a Category A site in Scotland with national importance and is currently a nominee for a UNESCO World Heritage Site.
Unique Features: This year is Forth Bridge's 125th anniversary. It underwent a major paint-job restoration from 2001-2011 and there are plans for a viewing platform and a thrill climb (gallery and videos at this site) to be opened in the next year or so. The Forth Bridge is also known for its red oxide paint, which was color matched during the bridge's restoration paint job (Figures 1-3 below).
Why was this bridge a success? The Forth Bridge is a success because it has fulfilled its purpose for 125 years and remained in good working condition. Additionally, it has become an internationally recognized bridge.
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| Figure 1: Full view of the Forth Bridge |
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| Figure 2: Train crossing the Forth Bridge |
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| Figure 3: The underside of the Forth Bridge (structural layout) |
Transportation Success Presentation
Sources:
http://www.britannica.com/EBchecked/topic/214233/Forth-Bridge
http://forth-bridges.co.uk
http://www.railway-technology.com/projects/forth-rail-bridge-firth-scotland/
http://www.forthbridgeexperience.com
Transportation Failure: Arroyo Pasajero Twin Bridges
Location: The Arroyo Pasajero Twin Bridges were located near Coalinga, California over the Arroyo Pasajero Creek.
When: The twin bridges were built in 1967 and they collapsed twenty years ago today, March 10, 1995.
Type of bridge/Significant attributes: I could not find the type of bridge stated outright, but I do know that the twin bridges included wing walls, vertical abutments, and three piers made of six columns each. A web wall was later added to provide extra support to the groups of columns.
Dimensions: 122 ft long
Cost: I did not find the original cost of the bridge. However, the bridge that replaced the Arroyo Pasajero bridges after they collapsed cost $6 million. Additionally, travel time lost due to the collapse cost local residents $550,000.
Unique Features: The bridges operated as a 4-lane interstate (Interstate 5).
Why did the Arroyo Pasajero Twin Bridges fail?
Several factors contributed to the collapse of the Arroyo Pasajero bridges. The main factors include flooding, lack of planning for a web wall, increased drainage, limited space for flow, long-term degradation, scouring, and lack of adequate steel supports for columns.
At the time the bridge collapsed, California was experiencing the effects of El Nino, which included relentless storms that led to major flooding. Several years prior to the collapse in 1969, there was another flood that lowered the bed of the creek 6 ft. A web wall was constructed after this flood to provide extra support for the columns. After construction, the Arroyo Pasajero Creek was connected by a manmade channel to Chino Creek. This channel increased the amount of drainage in Arroyo Pasajero Creek by 33%. Additionally, the creek width upstream of the 122 ft bridge was 300-400 ft. The flow of water in this larger width was limited by the bridge, leading to a build-up of water during the 1995 flooding. Between the time of construction and the time of the collapse, the land level had been reduced 10 ft by degradation (wearing down of soil). During the flooding, scouring (erosion of soil around supports) exposed a depth of the columns that did not have steel supports. These factors combined to undermine the strength of the bridges and the bridges collapsed.
Bridge replacement modifications and redesign: The twin bridges were effectively replaced in 10 days. The newly redesigned bridge was built with a railroad flatcar superstructure, steel supports, a concrete column foundation, and a steel grate surface covered in trench plates and rubberized asphalt (Figures 1-3 below).
Why were the Arroyo Twin Bridges a failure? They failed in their purpose to provide safe and reliable transportation. Additionally, they were not properly maintained, which led to the death of seven people.
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| Figure 1: Caption located on digital image. |
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| Figure 2: Replacement bridge after the twin bridges collapsed. |
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| Figure 3: Underside of the new bridge. |
Transportation Failure Presentation
Clarification: Today in class, I said the twin bridges were made up of two bridges, each carrying two lanes of one way traffic. However, this was an assumption based on the information I had read and collected.
Clarification: Today in class, I said the twin bridges were made up of two bridges, each carrying two lanes of one way traffic. However, this was an assumption based on the information I had read and collected.
Sources:
http://www.fhwa.dot.gov/publications/publicroads/98julaug/planning.cfm
http://www.nytimes.com/1995/03/12/us/heavy-rains-roll-their-destructive-way-down-california-coast.html
http://www.sfgate.com/news/article/I-5-Tragedy-Unites-Residents-Of-Rough-and-Tumble-3041270.php
http://www.fhwa.dot.gov/publications/publicroads/95fall/p95au2.cfm
http://isddc.dot.gov/OLPFiles/FHWA/010590.pdf
http://water.usgs.gov/edu/earthgwlandsubside.html
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