Union Pacific Missouri River Bridge

Union Pacific Missouri River Bridge
use	Railway bridge
Crossing of	Missouri River
place	Omaha ( Nebraska ) and Council Bluffs ( Iowa )
Entertained by	Union Pacific Railroad
construction	Truss bridge
overall length	533 m
width	10 m
Longest span	75 m
Construction height	14 m
Clear height	19 m
opening	1872, 1887, 1916
	location

41.249722222222 -95.917222222222Coordinates: 41 ° 14 ′ 59 " N , 95 ° 55 ′ 2" W.

The Union Pacific Missouri River Bridge , also known as Omaha Bridge , is a double-track railroad bridge across the Missouri between Omaha , Nebraska and Council Bluffs , Iowa . The truss bridge of the Union Pacific Railroad goes back to one of the first permanent railroad bridges over the Missouri from the year 1872, which then connected the first transcontinental railroad from Sacramento to Omaha with the east of the USA. It became an important railway junction at the end of the 19th century and the volume of traffic increased to up to 300 trains a day in the period that followed. Due to the rapid development of locomotives and freight volumes, it had to be rebuilt several times and in the meantime also served as a road connection, for which additional lanes were attached to its outer sides. The current steel bridge has existed in its current design since 1916. The operator is still the Union Pacific , which still uses the bridge for rail freight transport , including for transporting coal from the Powder River Basin in Wyoming and Montana .

First bridge in 1872

The Union Pacific's first Omaha Bridge from 1872 (single track)

With the completion of the Omaha-Ogden ( Union Pacific ) and Ogden-Sacramento ( Central Pacific ) railways in 1869, the need for a permanent railway bridge over the Missouri, where the connection to the east coast of the USA was built , grew at the eastern end of the first transcontinental railroad in Omaha was realized in a cumbersome and time-consuming manner using railway ferries . By the end of 1870, the Union Pacific had built the first temporary wooden trestle bridge , which was replaced by a single-track iron bridge by 1872 . This consisted of eleven 75-meter-long post truss girders (English: post truss , after its inventor Simeon S. Post, 1805–1872), which rested on ten pillars. These, in turn, were made up of two connected iron pipes with a diameter of 2.6 meters, which were driven down to the bed of the rock in the river bed and then backfilled. The construction of the bridge took a total of 1162 days and, at almost US $ 3 million, was one of the most expensive projects of the time.

The Union Pacific tried to refinance the construction costs through fees for use by other railroad companies. Due to the existing monopoly - it was only the third railroad bridge over the Missouri - the income amounted to US $ 15,000 per month. Due to the increase in settlement in the West and Midwest of the USA, the volume of traffic increased considerably and the weight of the increasingly powerful locomotives also increased, which forced the Union Pacific to think about expanding or building new ones ten years after the construction.

Second bridge 1887

The second Omaha Bridge built by George S. Morison by 1887 (double-track with additional lanes on the outside)

In 1885, the bridge construction engineer George S. Morison was hired to design a new double-track truss bridge that only reused a few bridge piers. In addition, he was able to shorten the bridge by more than 300 meters, as the continuously changing course of the Missouri river shifted westwards towards Omaha and the former bridge over the eastern floodplain could be replaced by a pile of earth. As central elements, Morison chose four 75-meter-long Whipple trusses with a track below (English whipple truss , after its inventor Squire Whipple , 1804–1888), which rested on five new stone pillars erected using caissons , followed by three shorter trusses with a track on top . The bridge also had two carriageways with footpaths on its outer sides, which were realized with wooden planks on side arms.

Construction work began at the end of 1885 and the trusses were erected and dismantled one after the other with the help of portal cranes after the new bridge piers had been erected. At that time, Morison was increasingly replacing the usual cast and wrought iron with the new material steel and was already using 40 percent of the four central trusses of the second Omaha Bridge . The work was completed in mid-1887, but the commissioning of the second track was delayed until the beginning of October due to the necessary double-track expansion of the access roads. At this time, the young Ralph Modjeski (1861–1940) also worked under Morison. After working with Morison for seven years, he later founded his own engineering office and, like his teacher, became one of the most important bridge engineers in the USA. The costs amounted to around US $ 850,000 and were therefore more than two thirds lower than for the previous structure, which had only been in use for thirteen years. Morison's bridge was only supposed to have existed for just under 30 years, as the locomotives and the freight transported were steadily gaining weight and the second bridge finally reached its load limit in the 1910s.

Third bridge 1916

Construction of the third Omaha Bridge in 1916. Using wooden scaffolding on both sides, the old trusses (left) could be replaced with the new ones (right) within a few hours by moving them sideways

The trusses of today's steel bridge in 2004

In the mid-1910s, Union Pacific engineers designed a new superstructure with an eight times higher load-bearing capacity than Morison's bridge, which was almost 20 percent above the requirements then necessary. Since the volume of traffic had increased to an average of 300 trains a day, a way had to be found to replace the trusses without major interruptions to train traffic. By the end of December 1916, the American Bridge Company erected the new steel lattice girders downstream on wooden scaffolding next to the stone pillars, and on December 23, around noon, the old girders were detached, moved to the same wooden scaffolding on the upstream side and then the new girders onto the stone pillars pushed. The first train was able to pass the bridge again after a ten hour break.

The current bridge consists of four 75 meter long Pratt truss beams (engl. Pratt truss , after the inventors Caleb and Thomas Willis Pratt, 1812-1875) with a bent upper flange and three smaller beams with straight upper flange and subsequent girder bridges of access roads, the parts of the replace former smaller trusses. The total length of the bridge is equal to Morison's Bridge 533 meters. The weight of the four central girders increased from a total of almost 2000 tons to almost 3600 tons due to the larger load capacity. The bridge has been in operation almost unchanged for over 100 years and is still used by the Union Pacific for rail freight transport, including the transport of brown and hard coal from the Powder River Basin in Wyoming and Montana , 40 percent of which are opencast mines of the US coal supply.

A Union Pacific freight train loaded with coal passes the now more than 100-year-old bridge towards Omaha (2006)

Web links

Commons : Union Pacific Missouri River Bridge - Collection of pictures, videos, and audio files

Union Pacific Missouri River Bridge. John A. Weeks III.
March 1872: First Bridge Across the Missouri River. History of Union Pacific.
Omaha Bridge, Spanning Missouri River, Omaha, Douglas County, NE. Historic American Engineering Record, HAER NE-6.

literature

Clayton B. Fraser: Nebraska City Bridge. Historic American Engineering Record, HAER No. NE-2, Denver, Colorado 1986, pp. 116-138.
George S. Morison: The New Omaha Bridge: A Report to Charles Francis Adams, President of the Union Pacific Railway Company. New York 1889.
Four Spans of Union Pacific's Omaha Bridge Rolled to Place. In: Engineering News-Record. Vol. 77, No. 3, 1917, p. 122 f.

Individual evidence

^ ^A ^b Clayton B. Fraser: Nebraska City Bridge. Historic American Engineering Record, HAER No. NE-2, Denver, Colorado 1986, pp. 116 f.
^ George S. Morison: The New Omaha Bridge: A Report to Charles Francis Adams, President of the Union Pacific Railway Company. New York 1889, p. 3.
^ ^A ^b Clayton B. Fraser: Nebraska City Bridge. Historic American Engineering Record, HAER No. NE-2, Denver, Colorado 1986, pp. 117-138.
^ George S. Morison: The New Omaha Bridge: A Report to Charles Francis Adams, President of the Union Pacific Railway Company. New York 1889, p. 11 f.
^ ^A ^b Four Spans of Union Pacific's Omaha Bridge Rolled to Place. In: Engineering News-Record. Vol. 77, No. 3, 1917, p. 122 f.
^ Union Pacific Missouri River Bridge. John A. Weeks III, accessed March 21, 2018.

[Fraser116f-1] A ^b Clayton B. Fraser: Nebraska City Bridge. Historic American Engineering Record, HAER No. NE-2, Denver, Colorado 1986, pp. 116 f.

[2] George S. Morison: The New Omaha Bridge: A Report to Charles Francis Adams, President of the Union Pacific Railway Company. New York 1889, p. 3.

[Fraser117f-3] A ^b Clayton B. Fraser: Nebraska City Bridge. Historic American Engineering Record, HAER No. NE-2, Denver, Colorado 1986, pp. 117-138.

[4] George S. Morison: The New Omaha Bridge: A Report to Charles Francis Adams, President of the Union Pacific Railway Company. New York 1889, p. 11 f.

[ENR-5] A ^b Four Spans of Union Pacific's Omaha Bridge Rolled to Place. In: Engineering News-Record. Vol. 77, No. 3, 1917, p. 122 f.

[6] Union Pacific Missouri River Bridge. John A. Weeks III, accessed March 21, 2018.