Eads Bridge

Design and Construction

Back   Next

Design of the Bridge

In his capacity as chief engineer, Eads assembled an engineering staff in the spring of 1867 and began to work on a schematic design for the bridge and on a preliminary cost estimate. The schematic design was presented to the bridge company's shareholders in Eads' “Report of the Engineer in Chief of the Illinois and St. Louis Bridge Co.,” published in May 1868. Engineering work continued after release of the 1868 report, with phased completion allowing construction to start on some parts of the project while design continued on others. The first masonry for the west abutment was installed in February 1868. During the following three years, while design of the superstructure was in progress, work began on the river piers, east abutment, and the approaches. The definitive set of working drawings was not issued until February of 1871.[1]

Schematic Design of 1868

As described in the 1868 “Report of the Engineer in Chief,” the schematic design features arch spans of 497, 515, and 497 feet. Each span is comprised of four parallel arch ribs spaced across the width of the bridge. Each rib consists of a top and bottom chord separated vertically by 8 feet and laced together by diagonal bracing. The chords were to be constructed as a pair of 9-inch tubes mounted side by side. At the piers, the arches bear on wedge-shaped skewback blocks which extend the height of the rib to engage both the top and bottom chord. In the schematic design, the railway emerges from the tunnel that carries it beneath downtown St. Louis and runs in a straight line across the bridge. This arrangement causes the train deck to hang below the arches at mid-span, cutting off the top of their otherwise graceful curves.

Final Design of 1871

Engineering work continued after release of the 1868 report and the design was still in flux in February of 1870, when the contract was signed with Keystone Bridge Company to fabricate and erect the metal superstructure. The definitive set of working drawings, issued in February of 1871, includes changes suggested by Keystone to simplify fabrication as well as a number of refinements introduced by Eads' design team.[3]

Architecturally, the most important change was to reconfigure the bridge so that the railroad deck no longer cuts off the crowns of the arches. This was accomplished by flattening the curve of the arches so that their summits are lowered by 4 feet. At the same time, the tracks were raised by 4 feet at the center of the bridge, tucking them neatly between the arch ribs. The decks, previously level, now rise in a gentle curve, up from the abutments to pass over the center arch. To prevent the descending legs of this curve from dipping below the crown of the two side arches, the riverbank end of each side arch is lowered 18 inches relative to the ends at the river piers.

Other significant revisions included changing the top and bottom arch chords from tandem 9-inch pipes into a single tube (first 13, then 18 inches in diameter); increasing the distance between the top and bottom chord of the arches from 8 to 12 feet; splitting the skewback blocks into separate fixtures for the upper and lower chords; and increasing the width of the highway deck from 50 to 54 feet and 2 inches. In the final drawings, the spans of the arches are given their “as-built” dimensions of 502, 520, and 502 feet.[2] [4] (See the Length of Spans page for discussion).

German Influence

Eads bridge is unusual among metal bridges in 19th century America in being an arch- instead of a truss-bridge. This reflects the outsider status of the design team. Eads had no prior bridge-design experience and his “first assistant engineer” Henry Flad, and “assistant engineer” Charles Pfeifer, were German-educated immigrants. Their design was influenced by the recently-completed (1864) Pfaffendorf railway bridge across the Rhine River at Koblenz (Coblenz), but differs from it in its size and in the use of fixed-end arches, cylindrical arch chords, and steel.[5]

Departures from the Koblenz Model

Although superficially similar to the Koblenz bridge; Eads Bridge incorporates a number of innovations not found in the German structure.

Equal Load on the Arch Ribs

At Koblenz, each span was made up of three parallel arches spaced across the width of the bridge with two rail-lines nestled between the crowns of the arches. The center arch, supporting part of both tracks, was more-heavily loaded than the two arches at the sides. Eads bridge has four parallel arches. With each track supported on its own pair, all of the arches are equally loaded and could be made from similar components. The 4-arch configuration has the further advantage that any one of the parallel arches can be taken out of service for repairs (The remaining three are sufficient to support the bridge). This capability has been used on several occasions when it was necessary to replace damaged arch components.[6]

Cylindrical Arch Chords

The top and bottom chords of the Koblenz bridge were built-up from rectangular metal bars and plates. At St. Louis the arch chords are round tubes, theoretically a more efficient distribution of material in compression members.[7]

The tubes are 18 inches in diameter. They are fabricated from steel segments assembled into a cylinder (similar to the construction of a wooden barrel) and bound together by a steel jacket. This design allowed the use of relatively small parts, a concession to the limitations of then-current steelmaking procedures.[45]

The outside diameter of all of the tubes is the same but the wall-thickness varies, with thicker walls located in more-heavily stressed parts of the arches and lighter tubes at locations where less strength was required.

Fixed-End Arches

The Koblenz bridge was a two-hinge design. Prior to completion of the bridge, the arches were supported on pivots, which allowed the ends to rotate slightly, relieving the secondary stress that would have been imposed by deflection. At St. Louis, the arches are firmly anchored to their supports, preventing rotation of the ends. This stiffens the arches, allowing them to be constructed using less metal than would have been needed otherwise. Rigid connection also gave the arches the ability to cantilever for some distance during construction. This enabled an erection strategy in which the incomplete arches were suspended from above, on cables, instead of relying on temporary shoring standing in the river.[8]

Indeterminate Design

Although structurally efficient; fixed-end arches are “statically-indeterminate,” a category of structures which are extremely difficult to model mathematically. Calculations for Eads Bridge required months of effort by a team of clerks (called “computers”) working under the direction of Charles Pfeifer. Three computations were made. The first applied the formulas originally developed for the two-pin arches at the Koblenz bridge. A second set of calculations looked at the behavior of arches with fixed ends. In the third pass, the ends of the arch were strengthened by increasing the sectional areas near the piers. Calculations were made for the dead load of the arch, for loads imposed by trains moving across the bridge, and for strains generated by temperature changes of ± 80° Fahrenheit.[44] To guard against errors and to reassure investors regarding the safety of the design, the calculations were peer-reviewed by mathematician William Chauvenet, who at the time was chancellor of Washington University in St. Louis.

(For further discussion of Charles Pfeifer's analysis, see the Theory of the Ribbed Arch page of this website).

Steel

Prior to Eads Bridge, steel had rarely been used as a structural material. In the few instances where it was used, it was confined to isolated components in structures that were otherwise fabricated from wrought iron.

Eads fully committed to the use of steel and specified it for every component of the bridge's primary load-path. It was used for the hollow tubes that comprise the upper and lower chords of the arches, the couplings that connect the tubes together, the pins through the couplings which attach other components to the arches, and many of the anchor bolts which secure the arches to the masonry piers and abutments. The greater strength of steel enabled these parts to be smaller and lighter than would have been required if they were made of iron, an efficiency that Eads considered a key to the success of the project.

In his 1982 article, John Kouwenhoven suggests that Eads may have learned about steel during the American Civil War, when his firm designed and built a fleet of ironclad gunboats for the United States government. According to Kouwenhoven, this work placed Eads in communication with the Navy Department at a time when the navy was investigating possible military uses of steel. It is not known if Eads' ironclads contained steel components, but a few years after the war, when Eads started working on the bridge, he was already familiar with the properties of the new material. From its inception, Eads Bridge was designed as a steel structure.[9]

Condition of the Steel Industry

In the late 1860s, when the bridge was designed, steel was a specialty product manufactured in small quantities for applications such as machine parts and cutting tools. In the United States, most steel was made using the crucible process, a method which could produce high-quality metal but which was inherently a small-batch procedure, ill-suited for making large components for a bridge. Despite the shortcomings of the process, Eads' specification called for crucible steel.[10] This was probably unavoidable. Bessemer steelmaking would soon prove to be capable of large-scale production but, at the time bids were solicited for the bridge, there were only a few small Bessemer facilities in the country and their output was fully committed to making rails for train track. (Andrew Carnegie's Edgar Thompson steelworks, which would usher in the era of mass-produced steel, did not open until 1875)[11] All of the steel used in Eads Bridge, both carbon and chrome alloy, was crucible steel.

Quality-Control

The transition from crucible to Bessemer steel-making coincided with a shift away from a craft industry and toward “scientific” production subject to explicit, quantified, specifications. Eads Bridge straddles this transition. The steel was made using the time-honored crucible method but was required to achieve targets for yield strength, ultimate strength, and modulus of elasticity; with these properties verified by laboratory tests.[12] Because quality control procedures had not yet been standardized, every aspect of the quality assurance program had to be negotiated between the bridge company and steelmakers, a lengthy and often contentious process. Equipment needed to make these tests was not generally available and had to be custom-built for the project. Testing machines, built to designs prepared by Eads' staff, were installed at the steel plant and in the bridge company's shops in St. Louis.[13]

Keystone Bridge Company

For several years before he was invited to participate, Andrew Carnegie had been tracking the St. Louis Bridge as a potential project for his Keystone Bridge Company. For Keystone, the St. Louis Bridge was attractive because of the promotional value of such a high-profile project. For the St. Louis Bridge Company, Keystone had the advantages of its technical expertise and its connections to prospective investors. As an inducement to closing the deal, Carnegie offered to personally help sell the bridge company's bonds through his connections in the financial worlds of New York and Europe. For this service, Carnegie received a commission in St. Louis Bridge Company stock.[14]

A contract for fabrication and erection of the metal superstructure was awarded to the Keystone Bridge Company in February of 1870. Iron components were obtained from Keystone's sister firm, Carnegie, Kolman & Company (operator of Union Iron Mills in Pittsburgh). Keystone engaged the William Butcher Company of Philadelphia (later reorganized as the Midvale Steel Company) as a sub-contractor to manufacture the steel used in the bridge. The St. Louis Bridge Company was responsible for the overall design, and was authorized by the contract to perform quality-control inspection and testing within Keystone's and their sub-contractor's shops and to reject work that did not comply with the specifications.[15]

Other Contractors

The Illinois and St. Louis Bridge Company acted as designer and construction manager for the overall project and constructed the foundations using its own forces. Other parts of the project were performed by separate firms under contract to the bridge company. In addition to Keystone, separate entities were engaged to construct the masonry abutments and piers, the-cut-and-cover tunnel under downtown St. Louis, and the approach viaduct on the Illinois shore.

Unlike the bridge, for which the St. Louis Bridge company provided a detailed design, the tunnel and the east approach viaduct were design-build contracts. The bridge company provided the general parameters, the construction firms were given considerable latitude concerning details.

Problems with Steel

Keystone's contract with Butcher Steel Company was signed in October of 1870 and production of steel components started, only to stall when the difficulty of the work became manifest. Although Butcher had produced acceptable metal in small samples, they could not maintain the required quality when making full-sized parts for the bridge. Some pieces cracked spontaneously before they left the steel plant. Others failed in testing at stresses far less than specified. After months of trial-and-error, the arch tubes and the large bolts which secure the arches to the piers were successfully manufactured only after Butcher's carbon steel was abandoned in favor of a proprietary chrome-alloy steel manufactured by Butcher under license from the patent-holder, the Chrome Steel Company of Brooklyn, NY. (The bridge company brokered this arrangement in order to expedite the work).[16] The couplings that secure the sections of the arch tubes, specified as steel, proved to be too difficult to make and were finally executed in wrought-iron. Wrought-iron was also substituted for some of the steel anchor-bolts at less-critical locations.

Foundations

The depth of water opposite St. Louis was normally in the range of 10 to 60 feet. The river-bed consists of sand with a few deposits of gravel.[43] The depth of solid rock varies from about 40 feet below the “City Directrix” at the St. Louis shore to more than 100 feet at the Illinois side of the river.[17]

Where it was necessary for a bridge to have piers in a river, 19th century bridge designers had two options. Ideally, the pier could be extended down to solid rock. Where this was impractical, the pier could be supported on piling (usually wood, sometimes iron) driven into the riverbed (Wood piling was protected from rot by the oxygen-free environment below the riverbed and could last indefinitely).

The design of the bridge's foundations was informed by Eads' previous career as a salvage contractor. Observations made while hunting for and recovering sunken steamboats convinced Eads that the erosion and transport of riverbed sediment might extend much deeper than was generally assumed by Eads' contemporaries. He concluded that the turbulence of the water sluicing around the bridge's piers would scour pits in the riverbed adjacent to the piers and that such pits might extend as much as 40 feet below the normal level of the riverbed, possibly all the way to bedrock. Given that the enormous cost of excavating to this depth could not be avoided, there was little to be gained by using piles. It would be best to simply keep digging, and set the foundations on solid rock.[18] The river piers and the west abutment, which are exposed to the current, would extend to bedrock. The east abutment and the piers of the east approach, which are inland and not exposed to the current, could be set on piling.

Construction started first at the west abutment. Bedrock was relatively shallow and the excavation was exposed to the river on only one side. A sheet-piling cofferdam was constructed on the river side of the site, a pit excavated to bedrock and pumped dry, and the foundation constructed. (See the "West Abutment" page for Ead's description of problems encountered while excavating for the foundation)

The river piers were more challenging because they were surrounded by water and must extend much deeper. In his 1868 “Report of the Chief Engineer,” Eads proposed to construct these piers using an enormous open caisson and a device he referred to as a floating cofferdam. This approach was not pursued. Shortly after completing the report, Eads took an extended vacation in Europe. While the Eads family was traveling, Eads took advantage of every opportunity to talk to European engineers and visit bridges under construction. Among the sites he visited were projects using pneumatic caissons, a recently-developed European technique for installing foundations. Eads was able to observe their operation and was encouraged to consider their use at St. Louis. When he returned, he redesigned the piers to take advantage of the new technology.[19]

Caissons

As designed by Eads, the caissons were enormous wood and iron boxes, of roughly hexagonal shape, about 9 feet tall and 60 x 82 feet for the river piers and 72.5 x 82 feet for the east abutment. The boxes had air- and water-tight roofs and walls and open bottoms. The iron-plate sidewalls extended above the roof to create a shallow tray which could float on the river like a barge. The lower extremity of the walls, at the open bottom of the box, terminated in an iron-shod cutting-edge that could be forced into the riverbed.

The caissons were constructed by Eads' associate, William Nelson (his partner in the salvage business and in the Civil War gunboat contract).[42] They were built at the Carondelet shipyard, just south of St. Louis; then towed to the construction site and anchored at the locations of the piers. A ring of “guide piles” was driven into the riverbed around each caisson to lock it precisely on-station, and a pair of pontoons, containing the machinery needed to operate the caisson, was moored alongside. Compressors on the pontoons operated continuously, pumping air into the caisson to displace the water and maintain an air-pocket in the lower chamber.

When the caissons were ready, masonry crews were ferried out and set to work, constructing the piers on the roof of the boxes. As the mass of masonry grew, the caissons were depressed deeper into the river. Additional iron plates were rivited to the side-walls, extending them as needed to keep the rim safely above water-level. Jack-screws suspending the caissons from the guide piles were slowly backed-out to control the descent and keep the caisson level. (Most of the weight of the caissons was supported by the buoyancy of the air in the lower chamber).

When the caissons reached the riverbed, more weight was applied to drive the cutting edge into the sand. Now workers could enter the chamber through an air-lock and walk around on the riverbed. After this, work continued in two directions. Men in the air-chamber hosed and shoveled sand out from under the caisson, causing it to settle into the riverbed. Meanwhile, overhead, the masons continued to raise the pier so that its summit was always near water-level and its growing weight could help to force the caisson deeper. Excavated material was ejected from the caisson using a sand pump (an Eads invention). Sometimes buried objects were encountered that were too big to fit through the pump. Logs and stumps were sawn up and passed out through the air-locks. Stones and boulders were stockpiled in the air-chamber and carried down with the work for eventual inclusion in the foundation.

When the caissons reached bedrock, the air-chamber and the communicating shafts up through the masonry of the piers were packed full of concrete to create the permanent foundation. (To save money, the air chamber at the east abutment was filled with sand instead of concrete. Eads argued that because this caisson is embedded in the riverbank, the sand will never be subjected to washing out, even after the iron plating has rusted away).[20]

Eads' caissons became the model for subsequent projects. In April 1870, Washington Roebling toured the east pier while he was working on the design of even-bigger caissons to be used at the Brooklyn Bridge.[21] Many features of Eads' caissons were replicated in the Brooklyn works, including the use of an iron-clad timber structure and the location of the airlocks in the caisson instead of at the head of the communicating shafts (Eads later sued Roebling for stealing the design).[22]

The caisson for the east pier was launched on October 17, 1869 and reached bedrock on February 28 1870, 95 feet below water level. The success of the caisson prompted Eads to revisit his decision to set the east abutment on piles. Instead, as with the river piers, it would be extended to bedrock using a caisson.

The caisson for the west pier was launched on January 3, 1870, while work on the east pier was in progress, and reached bedrock, 77 feet, 9 inches below water, on April 1 of the same year.

The caisson for the east abutment launched on November 3, 1870 and reached bedrock on March 28, 1871, 109 feet below the water surface.

The water depths are those measured on the day the caissons landed. Because the river level varies, a more meaningful dimension is depth below the project's reference elevation, the “city directrix”. These depths are; east pier – 90 feet below, west pier – 119 feet below, and east abutment – 128 feet below the directrix.

After completion of the foundations, work on the piers continued, pausing only to wait for delivery of the steel anchor-bolts which had to be built into the masonry before the piers could be finished. In the spring of 1872 all of the piers were ready for installation of the metal superstructure.[23]

The Bends

Decompression sickness (also known as “the bends” or as “caisson disease”) is a condition arising when the ambient pressure is reduced too quickly. Rapid release of pressure causes dissolved gases to come out of solution and form bubbles in the blood or within bodily tissues. Today, divers and other personnel working in pressurized environments avoid rapid decompression but when Eads Bridge was built, the cause of the bends was unknown. The airlocks were cycled as rapidly as possible so that workers could return to the surface quickly at the end of their shift.

As the caissons descended past 40 feet below water level, symptoms of the bends began to be noticed. Initially they were considered more of a nuisance than a threat (aching joints to be treated with copper bracelets and patent medicine). Below 60 feet, the frequency and severity of attacks increased and had to be taken seriously. Men were subjected to debilitating pain, temporary paralysis, and seizures. Usually the victims recovered but sometimes they were permanently impaired. Some cases were fatal.[24]

The bridge company attempted to respond. A physician was added to the staff (Dr. Alphonse Jaminet) and a clinic was fitted-out on one of the pontoons. Proceeding by guess-work and never clearly understanding the cause of the malady, the company instituted a regimen that helped somewhat. Time in the caissons was progressively reduced to as little as 1 hour at the river piers and 45 minutes at the east abutment (were an elevator was provided to ease the frequent trips to and from the surface). Workers were prohibited from working another shift for at least four hours after leaving the airlock and were limited to three work-shifts per day at the river piers and two work shifts at the east abutment.[25]

The company's initiatives seem to have been partially effective. After instituting the revised work schedule, the incidence of caisson disease was reduced (Fewer complaints and only one death while constructing the east abutment). Over the course of constructing the piers, 600 “submarines” worked in the caissons. 119 suffered symptoms of the bends. 14 of these cases resulted in the death of the victim.[26]

Dr. Jaminet never identified the rate of decompression as the culprit. He did institute a crude decompression rule: one minute for each six pounds of pressure (psi), but this was intended to limit ear damage while transiting the airlock not as a measure against caisson disease. One minute for six psi is too fast to have any effect against decompression sickness.

Erection of the Arches

Although Keystone Bridge Company was responsible for fabrication and erection of the arches, the method used to support them during construction was devised by Eads' “chief assistant engineer,” Henry Flad.

A partially-complete bridge is usually supported by temporary shoring standing in the river below. At St. Louis, this would be problematic. Shoring below the bridge would be subject to damage from the river's annual floods and ice-flows and would create an unacceptable obstruction to riverboat traffic. To avoid these problems, Flad proposed to suspend the partially-complete arches from above, using cables rigged from temporary wooden towers which would be erected on top of the piers.

The steel arches were flexible and deflected as construction crews moved around on them and as arch components were hoisted. They also squirmed as they were heated by the moving sun. Because of their dynamic character, provision had to be made for actively controlling the alignment of the half-arches as they grew toward each other. This was accomplished by adjusting the bracing rods between the parallel arch ribs and by varying the tension on the support cables.

Tension on the cables could be changed by raising and lowering the wooden towers, which were set on hydraulic jacks. All of the jacks at each tower were connected by pipes to a common master cylinder. Water pressure in the system, and thus the force applied by the jacks, was controled by attaching weights to the plunger of the master cylinder. Once the desired cable tension was set, the hydraulic system maintained it automatically, regardless of thermal expansion of the bridge and the cables.

When it was time to complete an arch, hydraulic pressure could be increased to pry the ends of the half-arches slightly apart so that the last section could be slipped in. This operation was critical because, to compensate for the compression of the arches under the weight of the bridge, each tube section was oversized by a factor of 1.0005221 (adding to about 3 inches over the length of each span).[46] Without the pre-load applied by the hydraulic system, the closure pieces could not be installed.

Keystone adapted the erection scheme but refused to accept responsibility for successful closure of the arches. It was agreed that, on the day that the last pieces were installed, Keystone's engineers would vacate the site and the bridge company's engineers would direct the closure operation. Keystone's crews began erecting the arches in June of 1872, with Keystone's superintendent Walter Katte, and the St. Louis Bridge Company's Henry Flad collaborating to supervise the work. Progress was delayed by slow delivery of steel components. As construction fell behind schedule, it became apparent that closure of the arches would occur during the hottest months of the following year. Eads worried that hot weather might cause the half-arches to expand so much that it would be impossible to fit-in the last pieces. To prepare for this, he designed adjustable closure pieces that could be shortened for installation, then screwed out to their full length prior to relaxing the shoring cables. A set of these couplings was prepared in the bridge company's shops and held in reserve.

The two center ribs of the west arch were ready for closure in September of 1873. As agreed, Keystone's engineers stayed home and Henry Flad supervised the closure operation. As Eads had feared, the weather was hot. After several unsuccessful attempts using the closure pieces provided by Keystone (including an attempt to shorten the arch by packing its entire length in ice), Flad resorted to Eads' adjustable couplings and successfully closed the span. Thereafter adjustable couplings were used for all of the arches. The final closure was made on December 18, 1873 – just meeting a deadline stipulated in the bridge company's bonds.

After the arches were closed, completion of the iron superstructure proceeded quickly. The decks were ready on April 18, 1874 but Keystone refused to release them to the bridge company until settlement of outstanding claims for payment. Negotiations dragged on until May 23 when Keystone finally vacated the bridge.

Construction of Approaches and Tunnel

As work progressed on the arches, the approaches to the bridge were also under construction. On the St. Louis side of the river, the tracks arrive at the bridge by way of a tunnel which extends under downtown St. Louis. The Illinois approach was an iron trestle which ramped gently down from the east end of the bridge to reach ground-level about 3,000 feet inland (the trestle was replaced with a steel structure early in the 20th century)[27]

The trestle-work of the east approach had no unusual features. The bridge company issued bid documents outlining the general configuration and detailed design was left to the contractor.[28] In March of 1873, after Keystone declined to bid on it, the work was awarded to the Baltimore Bridge Company. Construction went smoothly and the trestle was ready for traffic the following June, in time for the opening ceremony for the bridge.

Initially the bridge company hoped to entice the railroads to build the tunnel. When there were no takers, it was necessary for the bridge company to build the tunnel itself. A separate entity, the St. Louis Tunnel Railroad Company, was established to sell bonds for the tunnel project. Eads prepared bid documents and in October of 1872 a construction contract was awarded to William Skrainka and Company.

The 4,880-foot-long tunnel consists of parallel brick arches, one for each of the two tracks. It extends west from the bridge below Washington Avenue, then turns to the south under 8th Street to reach the Mill Creek valley near the present site of Busch Stadium. To achieve a workable turning radius, the tunnel departs from the public right-of-way and cuts across the block at the corner of 8th and Washington.

The tunnel was constructed using the cut-and-cover technique. First a 30 foot deep trench was excavated between the curbs of city streets, then the masonry structure of the tunnel was completed, and finally, the trench was backfilled and the streets restored. It was an inherently difficult project requiring the purchase and demolition of some buildings, temporary support of others, and wholesale re-routing of underground utilities. Boggy ground was encountered which made excavation difficult and required continuous pumping. Neighboring businesses, cut off from their customers by the open trench, were hostile and sued the tunnel company. The work was plagued by accidents, some fatal. Citing unanticipated costs, Skrainka and Company threatened to abandon the job when the tunnel was half-finished. A compromise was reached wherein Skrainka completed the portion of the tunnel south of Market Street and James Andrews, the contractor for the stone abutments of the bridge, took over the work to the north. At the time of the bridge's opening ceremony only one of the two tracks was installed and there were no connections beyond the tunnel's south portal.[29]

Proof-Loading

In June of 1874, the bridge was substantially complete and ready for final inspections. While adjustments and testing proceeded on the railway deck, the upper level was opened for sightseers who paid a nickel to stroll across the bridge. On June 14, to the delight of spectators, an unofficial test was conducted in which an elephant was led over the bridge. Popular legend had it that an elephant would never set foot on an unsafe structure. The beast judged Eads Bridge to be secure and ambled calmly across.[30]

On June 9 the first train crossed the bridge. Initially planned as a test of the straightness of the track, the excursion evolved into an impromptu opening ceremony when members of the press and selected guests were invited to ride along. As the train chugged across, the VIPs marveled at the view of the river, then choked on coal smoke as the train drove into the tunnel, which did not yet have a ventilation system.[31]

After this first crossing, the bridge was subjected to a series of progressively more-exacting tests. On the 29th, a locomotive was driven across the bridge, stopping at each joint in the track while the rail fastenings were inspected. The following day, a 50-ton locomotive and tender were again driven across, stopping every few feet while bridge company engineers measured the deflection of the structure. On July 1 a more elaborate test was conducted using a locomotive and 10 cars loaded with gravel and iron-ore, which were parked in various configurations on the spans while the survey crew made precise measurements. Testing culminated on July 2 with a public test in which 14 locomotives were maneuvered on the bridge while a vast crowd of spectators thronged the highway deck above. As on the previous day, the surveyors recorded the behavior of the bridge but the main purpose of the July 2 event was to generate publicity. (An estimated 50 tons of pedestrians strolling on the bridge and riding on the engines[32] must have played havoc with the deflection readings.) The measurements gathered during the three days of testing were found to agree with the deflections predicted by the design calculations and the bridge was pronounced ready to carry traffic.

During the tests it was observed that if one span was heavily loaded while adjacent spans were not, the unloaded spans bulged upward as the loaded span sagged. This shows that the adjacent spans, bolted to each other through the piers, act together as one continuous structure. Implicit in this observation is recognition that the masonry piers flex in unison with the metal superstructure. This aspect of the data was not widely publicized at the time (Victorians preferred to think of their masonry as unyielding) but was pointed out many years later in the memoirs of one of Eads’ staff, Carl Gayler, who was present during the tests.[33]

Grand Opening

On the 4th of July, 1874, a grand celebration was staged. Festivities kicked-off at 9 in the morning with an inaugural crossing of the bridge by a train of 15 cars carrying 500 distinguished guests. This was followed by a day of patriotic speeches and a 15 mile-long parade of “trades and occupations” which wound through the city and crossed and re-crossed the bridge. The finale was the discharge of $10,000 worth of fireworks from the deck of the new bridge as spectators watched from the riverbanks and from an armada of boats anchored below.[34]

Failure of the Illinois and St. Louis Bridge Company

As a business venture, the bridge was a failure. Burdened with debt, its success depended on cornering a large portion of trans-Mississippi rail traffic. This might have been possible in 1865, when the project was first conceived, but by the time the bridge opened in 1874 many of the railroads had well-established routes across the upper Mississippi, which gave them other options. The situation was made worse by poor timing. The bridge opened while the country was in the throes of the depression of 1873 – 79. With business slumping, railroads were not inclined to pioneer new routes through St. Louis.[35] Desperate to generate cash, the bridge company set high tolls which the bridge's arch-competitor, the Wiggens Ferry Company, was able to undercut, further shrinking the pool of customers. Only a handful of trains crossed the bridge during the first year.[36]

In April 1875, its reserves depleted, the Illinois and St. Louis Bridge Company declared bankruptcy. A group of the company's bondholders acquired the bridge at auction for $2 million and held it until they were bought out, two years later, by the newly-formed Terminal Railroad Association (TRRA), a consortium of railroads organized by financier Jay Gould. Both James Eads and Andrew Carnegie disposed of their shares in the bridge company well in advance of the bankruptcy,[37] leaving resentful investors grumbling about what would today be termed “insider trading”.

TRRA Ownership

The TRRA rationalized St. Louis' previously anarchic rail network and, in 1894, finally opened the long-delayed Union Station. With Eads Bridge integrated into a coherent rail system, traffic began to grow. By 1920 the bridge was carrying 26,000 carloads of freight and 3,000 passenger trains per month.[38]

Abandonment

Heavy traffic continued through the 1940s, when Union Station was the most heavily-traveled railroad depot in the United States, then tapered off during the 1950s and 60s as passengers abandoned rail in favor of air travel and the freeways. By this time, Eads Bridge was functionally obsolete. New generations of rolling-stock were too big to negotiate the bend in the tunnel and too heavy for the bridge's deck.[39] The construction of other bridges in the St. Louis area provided alternatives cheaper than continuing to maintain the aging structure. The rail deck was abandoned in 1974.[40]

Renewal

In 1989, in exchange for the MacArthur Bridge, the TRRA traded the derelict Eads Bridge to the City of St. Louis for incorporation into the city's Metrolink light rail system. The tunnel and rail deck were rehabilitated and re-opened for commuter trains in 1993. The highway deck was replaced during the late '90s and reopened in 2003. Finally, between 2012 and 2016, the bridge's superstructure was abrasive-blasted down to bare metal and re-coated, the first complete re-painting since the construction of the bridge.

After years of neglect, Eads Bridge is now the centerpiece of a regional transit system. It carries 290 commuter trains on a typical day[41] as well as automobile traffic between St. Louis, Missouri and East St. Louis, Illinois. The new upper deck includes public sidewalks that provide the definitive view of the river and of Eero Saarinen's Gateway Arch, which is immediately south of the bridge.

---

Footnotes

Back   Next