Source: Created by Rich Koors
For the construction of the New River Gorge Bridge, the West Virginia Department of Highways hired Michael Baker, Jr., Inc. to prepare the design package for the project. Michael Baker, Jr., Inc. both prepared the design package and acted as the construction manager throughout the project. This project, though monumental in bridge design, was not the first record-braking project for the Michael Baker Jr., Inc. One project that the company is probably best known for is the Trans-Atlantic Pipeline which runs from Prudoe Bay, Alaska to the port of Valdez. This enormous pipeline traveled a total of 789 miles and cost $7.7 billion, making it the largest privately funded venture in human history. Although Michael Baker, Jr., Inc. had a large amount of experience with large projects, designing a structure to span across the New River Gorge was no easy task.
Many obstacles were taken into consideration when designing the structure of the bridge. First, the Michael Baker, Jr., Inc. had to come up with the best design to minimize construction costs, minimize maintenance costs, and maximize aesthetic beauty. The first bridge design considered was a continuous truss design:
Source: Created by Rich Koors
This design, while economical, was rejected due to the enormous size of the piers. If constructed the piers would have extended to heights equal to and greater than those of skyscrapers. The second design for the bridge was a common suspension bridge:
Source: Created by Rich Koors
While this design met the needs of the project, it failed to meet budget requirements. The high cost was from the two piers shown which were each located 900 feet from the center of the bridge. Due to high costs, this design was rejected. The third consideration for the bridge was what is called a "jack knife" arch truss:
Source: Created by Rich Koors
This design met the requirements of the project and provided a very attractive structure to the gorge. However, due to the limited number of supports for the arch, excessive amounts of concrete were needed in the footers in order to stabilize the bridge. Consequently, costs for building the structure were too high. After many considerations, the design team from Michael Baker, Jr., Inc. came up with the final design for the bridge. The design not only provided beauty to the gorge, but it met all needs of the project and minimized costs for construction. The final bridge design was a simple arch span bridge. (Blair, 1991)
Source: Created by Rich Koors
With the concept of the bridge in mind, the Michael Baker, Jr., Inc. went on to devise a set of intricate drawings and specifications. Computations were made, calculating stresses on each steel member of the bridge, stresses on the abutments, lengths and sizes of each steel member, quantities of materials needed, etc. However, before the final drawings could be created, there were some problems to solve. First, two mined out voids were found beneath critical supporting piers for the bridge. To stabilize these voids, a method of gravel and grout was used to provide footing as shown below: (Baker, 1991)
Source: Created by Rich Koors
Normally in arch design, the bottom chords of supporting trusses carry the major
compressive stresses, however for this bridge, these chords would have become
too massive. This would not have been economical. To reduce the compressive
stresses on the bottom chords, the compressive stresses were shared between the
top and bottom chords.
With the structural design completed, the Michael Baker, Jr., Inc. chose unpainted
USS Cor-ten Steel to construct the bridge. This steel was stronger than ordinary
bridge steels and was better versus deterioration than most other steels. The
steel, when weathered, provided a rust-like appearance to the bridge and
developed a protective layer, which would resist deterioration in the future.
This rust-like appearance helped the bridge blend in with the environment. Once
all the potential problems had been solved, the engineers began to create the blue prints for what would be the largest arch
span bridge in the world, spanning 1700 feet and more than 876 feet above the
gorge's bottom. (Horstman)
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