Eads Bridge

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THE EADS BRIDGE

 

 

In 1867 a convention for the improvements of the Mississippi and its tributaries met in St. Louis. Even at this early date the people were beginning to see vaguely that the Mississippi Valley was destined to be the ruling section of the country. Eads in his address to the convention showed that he foresaw it plainly. It was at this time he made clear his remarkable plans for the bridge. A little later in the same year the long-talked-of bridge at St. Louis was at last begun. The population of St. Louis at this time was about 100,000 inhabitants. The estimated cost of the bridge, $736,000, caused consternation among the city officials and there was some delay in the plans.

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Several other schemes were suggested that would cost less. One of which, it is even said would have been carried out had not its projector died. In the winter of 1865-66 a bill was brought up in Congress to authorizing the bridging of the Mississippi at St. Louis. A Bridge was felt to be absolutely indespensable as when the river was frozen ferry service was blocked.

However, the opposition of rival commercial routes was so powerful that the bill was allowed to pass only after it had been so amended that it was supposed to require an impracticability. It declared that the central plan of the bridge must be no less than 500 feet long, nor its elevation above the city directix less than 50 feet. It was said at the time that the genius did not exist in the country capable of erecting such a structure. Still a span of over 500 feet had been built in Holland, and Eads felt there was no doubt as to the practicability of doing as well in the Mississippi Valley. His views were confirmed by the inauguration of two rival bridge companies about a year after the passage of the bill. One of these located in East St. Louis, after calling a convention of engineers, adopted a plan for a truss bridge. The other company from the first had Eads as its chief engineer. For a year a sharp contest was carried on between the two companies, confined however to the courts and newspapers. The Illinois company finally sold out to the St. Louis company. Mr. Eads knew that a truss bridge would have proven a failure, because the engineer who designed it did not arrange to base the foundation on the bed rock of the river. Eads knew that this must be done as he had been 65 feet below the river surface at Cairo, and there he had found the river bottom to be a moving mass at least three feet deep. Knowing all this and much more about what goes on under the rivers surface. Eads was absolutely convinced his bridge must be laid on bed rock, even if he had to go through 100 feet of sand to lay his piers on rock.

eads26.JPG (27395 bytes) He also saw that on account of the exceptional force of the current in its somewhat narrow bed at St. Louis, the masonry piers must be made unusually big to withstand it. Since they must be so big and sunk deep the cost would be great and Eads decided the fewer of them the better.

The central span was required to be 500 feet, with three spans the river could be crossed and three spans would require only four piers. The steel trusses 500 feet long would have to be made extremely heavy. Eads showed that a steel arch, the same length, while quite as strong would be lighter and much cheaper. The arches were finally determined on with two abutment piers, two river piers, and three arches of respectively 502, 520, and 502 feet long.

The greatest care and pains were taken in every direction. The stone, granite, and steel were both hunted up and tested by experts. The plans after being completed were gone over by Chauvenot, then chancellor of Washington U. who found them perfect.

Most of the big work, such as masonry and steel was given out on contract, and naturally there were several delays carried by the contractors. The piers were sunk to bed rock by metal caissons, that were open at the bottom but air tight everywhere else. These caissons when sunk to the bottom have the masonry of the pier built on top of them even while they are sinking. The workmen inside them keep removing the sand from underneath, and throw it under the mouths of pipes which suck it to the surface of the river.

One of the piers was sunk 100 feet below the surface of the river, through ninety feet of gravel and sand. This was the deepest submarine work that had ever been done.

In the dense atmosphere a candle when blown out would at once light again. For the first time telegraphic communications were held with the office on the shore. Out of 352 men employed in the various air chambers 12 died.

The superstructure consisted mainly of 3 steel arches, the largest that had ever been constructed. It was also the first to be built of spanded bracing, and the first to be built of cast steel. The Encyclopedia Brittannica called them "the finest example of a metal arch yet erected." They were built out from the piers from both ends to meet in the middle and were put into place without staging from below, this also was the first instance of such work. All the working platforms and machinery were suspended from temporary towers built on the piers, so that while the arches were being put up navigation below was not interfered with. This accomplishment along with the sinking of the piers presented some of the most difficult problems ever attempted by an engineer. One problem caused by the fault of the contractors presented itself when they came to insert the central tubes to close the arches. The tubes were found to be two and a half inches too long to go in, although they would only be the required length after they were in.

Eads solved this problem by cutting the tubes in half, joining them by a plug with a right and left screw. Then he cut off their ends, for the plug would make them any required length by inserting or with drawing the screws a little. It would have been much cheaper not to use this device, his assistants tried for hours to shrink the tubing by ice applications to get the arches closed. There is a popular tradition that they succeeded, but the weather was so hot they did not. Any part of this steel work can safely be removed and replaced. This was another structural feature original in this bridge. Mr. Eads took care to patent all these special innovations.

One curious detail connected with the building of the bridge in that the Milwaukee, a double turreted gun boat, which Eads had built, and had served in the war was bought from a junk dealer and her iron hull was used in making the caissons. eads27.JPG (28357 bytes)

On Jan 10, 1874 Hackett and Case, contractors were awarded the contract to fill the eastern approach. Both approaches cost approximately $1,000,000. In 1874 the bridge was finished. After it had withstood the severe tests put upon it, it was formally opened on the 4th of July. The celebrations held that day both in St. Louis and East St. Louis was the first public outburst of approval given to Eads work. The strength of the structure was demonstrated when the great tornado of 1896 failed to do any serious damage to the piers.

The building of Eads Bridge marked an era in bridge building, and while most of the credit goes to the brilliant engineer James B. Eads a great deal is shared by the men who risked and lost their lives in the hazardous work of erecting the spans over wide stretches of space, that astonished in its construction the entire civilized world.

 

Credits:

Field Worker: Edward Condon

Bibliography: East St. Louis Gazette 1872-74-75

Life of James B. Eads by Louis How -- 1900

Houghton-Miflin Co. Publishers New York City N.Y.

 

 

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