he Eads Bridge was, perhaps, the connected together to form a polygon of 800 best-known bridge of the 19th century sides.” Upper and lower arches were to be con- HISTORIC after the Brooklyn Bridge. A bridge nected by trussing, and the arches were to be fixed across the Mississippi River had been at the ends making them statically indeterminate. Tprojected as early as 1839 when Charles Ellet The easterly approach in Illinois consisted of a STRUCTURES Jr. (STRUCTURE, October 2006) proposed long iron viaduct with masonry arches flanking a 1,200-foot span suspension bridge. John A. the end spans of his arches. Railroad tracks were Roebling (STRUCTURE, November 2006) also on the lower deck, and roadways and pedestrian significant structures of the past proposed a hybrid bridge, with a pier at mid- walkways on the upper deck. river, a short time later. The St. Louis and Illinois In the meantime, Lucius Boomer was also pro- Bridge Company was formed in 1855, but noth- posing a bridge in the same area under the name ing was done until February 1864 when the State of the Illinois and St. Louis Bridge Company. He of Missouri granted a charter. James B. Eads was had Simeon Post work out a design consisting named Chief Engineer on March 23, 1867, after of six wrought iron Post Trusses with two spans he submitted preliminary plans in early March. of 368 feet and four of 264 feet. To promote his By May 1867, Eads decided to build his bridge plan, Boomer called® a convention of engineers to as a three-span arch bridge over the Mississippi look over all plans but with special attention to River with the arches made of steel. To assist his plan. The Convention favored Boomer’s plan him, the Company named Jacob Hays Linville and recommended in their Report spans of no (STRUCTURE, July 2007) of the Pennsylvania more than 350 feet. Eads went on the offensive Railroad and Keystone and responded with “If there were no engineer- CopyrightBridge Company as a ing precedent for 500-feet (stet) spans, can it be consulting engineer. possible that our knowledge of the science of engi- Eads Bridge at St. Louis The design was based neering is so limited as not to teach us whether on a bridge across the such plans are safe and practicable? Must we admit Rhine River at Koblenz that because a thing never has been done, it never By Frank Griggs, Jr., Dist. (Coblenz), Prussia. can be, when our knowledge and judgment assure M.ASCE, D.Eng., P.E., P.L.S. Eads first design had a central span of 515 feet us that it is entirely practicable? This shallow and two flanking arches of 497 feet, with a mini- reasoning would have defeated the laying of the mum clearance of 50 feet above high water. He Atlantic Cable, the spanning of the Menai Straits, recruited Henry Flad, Charles Pfeifer, and W. the conversion of Harlem Lake into a garden, and Milnor Roberts as his assistant engineers. When left the terrors of the Eddystone without their Eads mademagazine his design known to the public in warning light. The Rhine and the sea would still S T1867, Rthe St. LouisU Democrat C wrote, T “What Ube alternately R claiming E dominion over one-half a triumph for St. Louis, the noblest river, the of the territory of a powerful kingdom, if this most glorious bridge, and the finest engineer miserable argument had been suffered to prevail in the world. His arch ribs were to be made of against men who knew, without ‘an engineering steel in the form of steel tubes in straight pieces precedent,’ that the river could be controlled, Dr. Frank Griggs, Jr. specializes in the restoration of historic bridges having restored many 19 th Century cast and wrought iron bridges. He is a Professor Emeritus of Civil Engineering at Merrimack College in N. Andover, Massachusetts and is currently an independent consulting engineer. Dr. Griggs can be reached at [email protected]. Eads Bridge with St. Louis Arch in the background. Courtesy of HAER. 18 December 2017 shifting sands of the the arches in bars of 9 feet length, and of such Mississippi River bed, form that ten of them shall fill the circumfer- he insisted his founda- ence of a 9-inch lap-welded tube one-eighth tions rested on bedrock inch thick, in the manner that the staves of and looked at various a barrel fill the hoops. This would virtually methods to accomplish form a steel tube 9 inches in diameter and of this. Bedrock on the west 6 inches bore, the steel being about 1½ inches abutment was near the thick, and would be much less expensive than surface, so it presented if the tube were rolled or drawn in one piece. no problems. His east The manufacture of the steel in such small and west piers, however, bars will ensure a more uniform quality in the would have to be sunk to metal, and in the tube each bar will be sup- depths of 95 feet and 86 ported against deflection in every direction. feet below the river sur- The tubes will be retained in their positions face. His east abutment by an effective system of bracing, which will would have to reach a sustain the voussoirs® or pieces against which depth of 110 feet. the tubes are butted throughout the arch... Eads learned about The tubing in which the steel bars will be pneumatic caissons on enclosed will effectually protect the latter from a trip to Europe. Even the weather.” though no one had ever His tubes were made of steel staves covered Copyrightused them at the depths with a steel casing similar to wooden barrels. required at St. Louis, he The length of staves varied, as did the thick- decided they were the ness. Eads had to compromise his original only possible means to specifications. He had significant problems reach bedrock. While in getting the quality steel he wanted for placing the foundations, the staves as well as for the couplings that 14 men were lost, mostly connected the tubes. Once the staves were on the west pier, to what encased, he had to mill the ends to ensure East pier caisson. was to become known as full bearing from one set of staves to the next. and a curb put upon the ocean itself.” The caisson’s disease or the bends. By two bridge companies later merged. May 1870, all of the foundations When Linville saw the preliminary design, weremagazine in place, and Eads could he wrote, “The bridge if Sbuilt uponT these Rbegin erectingU his superstructure.C T U R E plans will not stand up; it will not carry its His original arches were doubled own weight… I cannot consent to imperil steel tubes, top and bottom, with my reputation by appearing to encourage diameters of nine inches. He later or approve its adoption. I deem it entirely changed this to single tubes with unsafe and impracticable, as well as in fault 12-inch diameters, and even later in the qualities of durability.” Linville later, to diameters of 18 inches. He as Chief Engineer of the Keystone Bridge also changed the vertical spacing Company, would be in charge of building between the top and bottom tubes the superstructure of the bridge. from 8 to 12 feet, as well as having When making a case for his bridge, Eads told the lower arch come up tangent his investors that he could build the bridge to the deck chords of the railroad for $3,000,000 and have it opened for traffic tracks. The spans were revised to within 3 years. He had never built a bridge 520 feet on the center span and before, especially a bridge that was going to 502 feet on the flanking spans. have a great deal of steel in it. Steel was used Transversely, the two center arches for many years, but not in bridge building would be 13 feet 9½ inches apart or major building construction. Wrought and the outer arches 15 feet 1¾ iron by this time had generally replaced cast inches off the center arches. iron and wood in bridge construction, with He knew the uniqueness of his much of the progress attributable to Linville use of steel and in 1867 wrote: and the Keystone Bridge Company plus the “To ensure a uniform quality and Phoenix Bridge Company, the Detroit Bridge high grade of steel at the lowest Company, and others. prices, and at the same time avail His first construction task was to place myself of the advantages of the foundations for his two river piers and two tubular form of construction, I abutments. Given his knowledge of the propose to have the steel rolled for Coupling and pin to connect diagonals to tubes. STRUCTURE magazine19 December 2017 He also had to cut-in the threads to receive that was used in ensuring success, expressed the structure, whose completion you sig- the couplings. He retained Theodore Cooper their gladness that my mind was relieved by nalize so notably…” (STRUCTURE, April 2011) to handle the the occasion. I felt no relief, however, for I The bridge ended up costing $6,536,729, fabrication of the staves and couplings. knew that it must go there safely…Yesterday twice as much as Eads originally estimated. Cooper was later in charge of the erection friends expressed to me their pleasure at the With construction starting in 1867 and open- of the tubes. thought that my mind was relieved after test- ing on July 4, 1874, the bridge had taken Since falsework could not be placed in the ing the bridge, but I felt no relief because I seven years to build, also more than twice river, Eads developed a way to build the had felt no anxiety on the subject.