Omaha Daily Bee Newspaper, March 15, 1903, Page 33

S - —— Building a Missouri River Bridge BUILDING MATERIAL ON SH ORE.—Photo by a Staff Artist. HE MOST important bridge con- struction in progress along the Missouri river is the rebuilding of the Omaha Bridge and Ter- minal company's structure, now owned by the Illinois Central Railroad company. The bridge is the northernmost of the three that span the river at Omaha and is gemerally kffown as the East Omaha bridge, extending from that section of the city to Council Bluffs, being entirely in the state of Iowa. It is about 1,620 feet long and when flliished ‘Will have cost close to $1,000,000. i 4 The bridge will consist of two Immense draw-spans each 520 feet long, and nife fixed steel spans, and will ‘be wide enough to accommodate two rajilway tracks within the trusses. Provision will be made for outside cantilever roadways for electric cars, highways and pedestrians, as the charter under which the right to build the bridge was granted spécifies that i must be open at all times to this kind of traffic. The roadways will not be put on at once, as the railway business for some time to come will demand but one track, leaving room on the bridge proper ror other pur- poses. When the present bridge was constructed in 1893 lees than ome-third of it was in- tended to be permanent. That portion is the draw-span and pivot pier on the Iowa side of the river, where the deep channel then existed. The span, 520 feet long, was then the biggest draw-span in the country, and at present has but one peer—that in the Hudson river at Harlem. Original plans contemplated replacing the temporary part of the bridge in seven years. The portion that is to be replaced consists of three 192-foot fixed through spans and 550 feet of timber trestle. It was not then intended to have two draw-spans, a permanent 560- foot fixed span being planned for the Ne- braska side. Constant veering of the river channel changed these ideas, and a decision was reached to build a draw-span, duplicating the first one, and spanning the river by these two immense swings. Together they will bridge the stream from shore to shore, and ‘unless the main channel seeks a route outside the present river bed the new bridge always will make possible the passage of water craft. The channel now is gradually leaving the east side of the river at this point. The new span will be heavier and larger than the old one and capable of sustaining greater weight. The weight of the pres- ent span is 2,768,000 pounds, while the metal and other material in the new one will tip the scales, if such a thing were possible, at 3,900,000 pounds, and is built to carry 8,020 pounds per lineal foot to the 6,100 pounds per lineal foot of the span that was bullt ten years ago. On the ground on the Nebriska side o? the bridge there will be eight spans of eteel girders resting on seven masonry piers and & masonry abutment, each standing on a base of wooden pilés driven forty feet into the ground. There will be one similar pier and one abutment on the lowa side to carry another short steel span. In the center of the river will be a pier of ma- sonry, 18x53 feet In size, upon which the inner ends of the draw spans will repose. It will rest on a pneumatic caisson and cofferdam, eighty-four feet below the sur- face of low water., The west end bf the Nebraska span will rest on a similar pler 16x47 feet in size, the foundation for which has already been sunk, complete, to a depth of seventy-four feet. The pneu- matic caisson system was used in sinking the foundation for the masonry for this pler. Largest of all plers in the new work, however, is the pivot pler for the new draw-span. This, like the other pivot pier, will be forty feet in diameter and will rest upon concentric twenty and forty-foot steel cylinders, one within the other, and both filled with steel bracing and concrete. These cylinders will not be sunk by cais- scne, but will be forced into the river bed by open dredging through the big twenty-foot hole in the center. This method was employed in forcing down the foundation for the present pivot pier, and though it was new then, it worked satis- factorily. The present bridge is under contract for completion June 1. It will hot be finished by that tithe, however, and 1t may be well into next winter before”it is. Construc- tion was begun in*September last,’and has been pushed forward as rapildly as possible, but delays; to material and the shortage cf men have retarded progress. At pres- ent there are about 150 men at work on the “bridge, and twenty-five or thirty more could be used. » Waddell & Hedrick, consulting engineers of Kaneas. City, designed the old and the new bridge. They are superintending the work through Mr. M. J. Maher, engineer in charge. The Foundation and Construction company of New York has the contract for the substructure and Mr. George ' Adgate is_in charge. The American Bridge com- pany holds the contract for the super- structure, or steel work. Their business will come later and the sending of ma- terial to Omaha has not been started. . Knowing that the wooden plera and cheap construction of the west two-thirds of the bridge would not last more than a few years, the designers arranged the present bridge so that the new parts can be built without interfering with traffic in any way. At present the bridge crosses the stream several degrees removed from right angles. The new bridge will go straight across, this being possible with- out entire reconstructicn, because the per- manent portion is a draw-span, which can be swung into alignment at pleasure. Bridge building is an occupation that re-~ quires immense capital, all the science that can be brought to bear and the services of many skilled and unskilled workmen. To the engineers and the construction su- perintendents it brings perplexities ana cares that cause loss of sleep and the per- manent wrinkling of foreheads, while to the workmen there are evident dangers to life and limb. Resourcefulness and a readi- ness to meet and to subdue new conditions are needed in bridge building, and the knowledge that thousands of dollars hang in the balance do not reduce the responsi- bilities Wha! it means to make a big bridge is apparent from an observation of the busy outdoor workshop that nestles close up under the embankments of the approaches on the river shore at East Omaha. Several acres of ground are taken up with the work of various kinds. Huge piles of crushed rock and frozen sand, in and out of railway cars, barrels of concrete, heaps of coal and nondescript tool and engine shacks give the place a disorderly and a busy air, while great ptles of evenly cut blocks of sandstone from Kettle river, in Minne- sota, stand out in straight-laced relief against the confusion. The pile driver pushes long sticks of wood into the ground, with the ald of a hydraulic pipe; donkey engines pant everywhere and pulleys and blocks groan as cranes swing heavy loads into place. A compressed air pump is coughing at- mosphere 1nto the caissons below the sur- face and spitting out a broken stream of sand which the diggers are loosening be- low. One gang of men is thawing out frozen sand; another is mixing concrete, while in the snug little tar paper-covered shanties of the building captains, clerical forces of young men are continually going over plans and making and cashing time checks and doing other kinds of labor with brain and TRAMWAY FROM SHORE TO C AISSONS.—Photo by a Staff Artist. pen. In a little dressing room just off the caisson top the men who come out of the air chambers doff their muddy, wet cloth- ing and swallow hot coffee that is prepared by a small boy. Building the piers and their foundations below the water is a subject that is in- teresting. Great engineering skill is in- volved and in the pneumatic caisson method of sinking the foundations there is great danger to the laborers. One of the two foundation piers for the East Omaha "bridge has been finished, but the larger one is in progress, and the river bed is being removed below the surface of low water. It will go eighty-four feet before the work is stopped. The smaller pier, which is close to the -west shore of the river, was sunk only seventy-four feet, but it is two feet shorter and six feet narrower than the pile of concrete that is now going down slowly day by day in the center of the stream. i 3 The caissons for the bridge were made by constructing the working chamber of twelve-inch timbers, three thicknesses being used for the walls and the ceiling. The lower timbers are beveled to a cutting edge and reinforced and protected by iron plates. Strong braces protect the working chamber from possible collapse. There is, of course, no floor, as it is through this cavity that the water and dirt and rocks are sucked up, so that the foundation may be lowered. On top of the working cham- bers is built, section by section, a heavily timbered framework of the same dimen- sions, also braced inside, and intoe which is placed concrete and stone welded so firmly together that the material will last longer than solid rock. These layers are called coffer dams and are put on as the caisson sinks into the river bed. Piercing the solid mass is a four-foot cylinder having two ladders to the working chambers below. Through this the caisson men enter and make their exit, and through it is hoisted the debris that cannot be forced through a four-inch pipe. Sand and gravel are blown out through the pipe by the force of compressed air, by which means, also, air is provided for the work- men. The top of the big vertical cylinder is locked by mechanism so that no air can get through it. If air did penetrate into the working chamber, it and the cylinder would soon be choked with dirt and water from underneath. Of course, it {s dangerous for the men to work in caissons. The history of bridge building is full of the disasters and sudden death that have overtaken them. It is not the llability of the thousands of tens of concrete above them falling in, or. any- thing of that kind, but the tremendously high air pressure, that counts. The decper they go under the water the higher the air pressure becomee, averaging about one pound to every twenty-seven inches of de- scent, At seventy-four feet, or the extreme depth of the caisson already in, it was about thirty-two pounds. Men have worked in atmosphere that weighed fifty-two pounds to the square inch, but the thirty-two-pound pressure was enough to kill one delver who worked on the Omaha bridge and to make very sick and patients in the hospital several other men. The man who died was Stephen Mattox, and the occurrence was chronicled in the newspapers. He had been at the business but two days when it proved too much for him, although to all appearances he was a strong man, Concerning the Mr. George Adgate says: “Mattox was the first man I lost, though I have sunk fifty-five pneumatic caissons., It is difficult to guard against such cares Great size and physical strength seem to make little or no difference in the work, small, wiry men getting along better many times than large ones. As a general propo- sition men with weak hearts or weak lungs have no business in a caisson, but the best of men in the best of condition are often- times overtaken. It is paralysis that kills them. A man stricken with caisson- paralysis never recovers. Another afMic- tion, which seldom is fatal, is caisson- fever, or what the men call ‘the bends.’ This causes thcm to become perfectly lmp and helpless. In either case the trouble is caused by noncirculation of the blood and in paralysis by the bursting of blood ves- sels.” d There is always a lot of water in the calsson chamber and the men slop about in high boots, and when they come out they need the clean clothing and a chance to wash that which they take off in the trough of warm water that is provided. Their work is lighted by electric bulbs and they are made as comfortable as possible. At pres- ent thirty men are working in the calsson in the center of the river. They labor in equal squads in three-hour shifts. As they go deeper the hours of work will be lessened, accordingly as the air pressure increases. They are pald $2.50 a day for the work at present. When they were down seventy feet in the old caisson they were getting $3 a day for four hours’ work, two hours at a stretch. In some places it has been necessary to pay enor- mous wages to induce men to work in the caissons, but there have been plenty of laborers willing to risk their lives for little more than ordinary pay so far at Omaha Most of the caisson men make a business of it and none belongs to this city. When they have completed their work the ingress cylinder will be filled up tight with concrete and the cofferdam founda- tiou will be ready for the sandstone ma- sonry in ponderous blocks above. It is a fact not generally known that these sec- tions of stone are carefully numbered and cut, each to fill a separate niche in the design of the whole pler. The blocks range from two to three and one-half feet in thickness, and are from three to five feet long, weighing several tons aplece. BEach has been cut carefully and a place marked for it in the plan. The masonry above the water is not solid sandstone. Only the outer walls are of this material, and this is to resist the disintegrating action of the elements. Inside the inevitable concrete is resorted to, the whole being welded to- gether by it. The men who are putting in the superstructure for the new bridge say that it will last forever, even the bard pine sheathing of the cofferdam never rotting as long as it is covered by water, or is in the ground under the water, For the pivots an entirely different method of inserting the plers is to be employed. The huge steel cylinders, tho outer one forty feet in diameter and the inner twenty feet through, will be built at the water's edge. The two are united by a conical diaphgram at the bottom. They will be braced by steel struts and the egpace between the inner and outer cyline ders will be filled with concrete as rapidly as built. There is a cutting edge at the bottom, and with the welght on top, which will be immense, the thing will sink, as big dredges scoop out the river bed in the center. In case additional excavating powers should be required, the hydraulic system wi!l be used, provision being made for a series of water jets around the cutting edge. The present pivot pler was sunk in this way. There i no chance for loss of life and the method is quick and satisfactory. The big cylinders will go down 120 feet below the water when it is at low mark, and will contaln approxi- mately 11,000 tons of metal, valued at about $35,000. On this will go the sightly blocks of sandstone and the concrete fill= ing. Sixty-horse power electric motors, make ing 250 revolutions per minute, will operate 3 (Continued on Seventh Page.)