Categories Galloping Gertie (1940) Tacoma Narrows Bridge (1950) New Tacoma Narrows Bridge (2005)
Designer Leon Moisseiff Dexter R. Smith

Charles E. Andrew

United Infrastructure Washington
Built By The Pacific Bridge Company, Bethlehem Steel and John A. Roebling's Sons Company Bethlehem Pacific Coast Steel Corporation and John A. Roebling's Sons Company United Infrastructure Washington
Cost to build 6.4 Million 14 Million 350 million (est.)
Construction Started 1938 1949 2001
Construction Completed July 1, 1940
October 14, 1950
2005  (est.)
Total Structure Length 5,939 feet 5,979 feet 5,400 feet
Suspension Bridge Section 5,000 feet 5,000 feet  
Center Span 2,800 feet 2,800 feet 2,800 feet
Second Deck Capabilities No No Yes
Shore Suspension Spans (2), each 1,100 feet 1,100 feet  
East Approach and Anchorage 345 feet 365 feet  
West Approach and Anchorage 594 feet 614 feet  
Center Span Height Above Water 195 feet 187.5 feet  
Width of Roadway 26 feet 49 feet 10 inches  
Capacity of Roadway   60k cars per day  
Width of Sidewalks(2), each 5 feet 3 feet 10 inches  
Diameter of Main Suspension Cable 17.5 inches 20.25 inches  
Weight of Main Suspension Cable 3,817 tons 5,441 tons  
Weight Sustained by Cables 11,250 tons 18,160 tons  
Number of No. 6 Wires Each Cable 6,308 8,705  
Weight of Shore Anchors 52,500 tons 66,000 tons  
Total Length of Wire   20,000 miles  

Towers

Height Above Piers 425 feet 467 feet  
Weight of Each Tower 1,927 tons 2,675 tons  

Piers

Area 118 feet, 11 inches by 65 feet, 11 inches 118 feet, 11 inches by 65 feet, 11 inches  
East Pier, Total Height 247 feet 265 feet  
East Pier, Depth of Water 140 feet 140 feet  
East Pier, Penetration at Bottom 90 feet 90 feet  
West Pier, Total Height 198 feet 215 feet  
West Pier, Depth of Water 120 feet 120 feet  
West Pier, Penetration at Bottom 55 feet 55 feet  

Comparison of the 1940 and 1950 bridges

 

1940 Roadway

Every reasonable precaution was taken to stabilize the structure and insure against any possibility of noticeable motion. One of those precautions, and a feature unique to this bridge, is the design of the roadway deck. Open steel grid slots were installed between each of the four traffic lanes and at both curbs. These open steel gratings function as vents to relieve oscillations created by passing wind. The gratings are bonded to the concrete to preserve slab continuity across the full roadway. In tests the use of these slots was an effective method of reducing the forces which cause oscillation and, consequently, constitute a large factor in stabilizing the structure.

1950 Roadway

 

The two main channel piers were undamaged during the failure of the original bridge and were used to support the second bridge with only minor modifications to the concrete pedestals under the new steel tower legs. The original construction of Pier 5 was one of the most difficult ever attempted, establishing a world record for depth of water in which a caisson had ever been landed. Water depth, along with tidal currents of nine miles per hour at the site, required extreme caution and ingenuity on the part of the engineers and contractors. Thirty concrete anchors, each weighing approximately 600 tons and connected to the caisson with 90 one-inch diameter wire cables, were required to hold the caisson against the current. At times the level of water at one end of the caisson would be seven to eight feet higher than at the other. Holding construction barges alongside the caisson was extremely difficult. Steel cutting edges were attached to the bottom of the caisson. After the caisson was lowered to the bottom of the channel in 135 feet of water, the cutting edges assisted in penetrating through 90 feet of sand, gravel, and boulders where the bottom of the caisson was finally positioned at a depth of 225 feet below mean low tide. Lightweight concrete was used in the roadway deck of the present bridge to lessen the load on the piers. However, the total superstructure weight of the present bridge exceeded the first bridge by approximately 1.6 times per lineal foot. The designers determined that this additional weight would not cause excessive overloading of the foundations. The original anchor blocks were also used in the second bridge, but were modified substantially due to the greater weight of the superstructure. This weight increased the horizontal force in the main cables from the original 28 million pounds to 36 million pounds. In addition, the new cables were spaced 60 feet apart compared to the original 39 feet. The concrete anchorage was modified by removing the sides and blasting to the top of the footing blocks. Then, new anchor bars were installed for the main cables. In addition eight feet of concrete was added on each side, and extending the back of the anchor 20 feet to its full height. The additional width and length, in effect, provided a yolk or "U" configuration around the old concrete core that remained.

 

click here to view the blueprint (link opens in new window)

Cross section drawing of a completed tower pier ready for erection of steel tower. (1940)

Completed steel towers. (1940)

Showing strand former and support used in fabricating main cables. (1940)

Primary State Highway No. 14. (1940)

Construction of the second bridge
Toll Booths just visible in lower right. (1962)
The Tacoma Narrows Bridge became toll free on May 14, 1965.

Tacoma Narrows Bridge Engineering Record (839k.pdf)