The Silver Bridge was an eyebar-chain

suspension bridge A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...

built in 1928 which carried U.S. Route 35 over the

Ohio River The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its river mouth, mouth on the Mississippi Riv ...

, connecting

Point Pleasant, West Virginia Point Pleasant is a city in and the county seat of Mason County, West Virginia, United States, at the confluence of the Ohio River, Ohio and Kanawha River, Kanawha Rivers. The population was 4,101 at the 2020 United States Census, 2020 censu ...

, and Gallipolis, Ohio. Officially named the Point Pleasant Bridge, it was popularly known as the Silver Bridge for the color of its

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

paint. On December 15, 1967, the Silver Bridge collapsed amid heavy rush-hour traffic, resulting in the deaths of 46 people, two of whom were never found. Investigation of the wreckage soon pointed to the failure of a single eyebar in one of the suspension chains as the primary cause — a finding noted in a preliminary report released within 10 months of the collapse. However, to explain why that eyebar failed — a failure triggered by a flaw just deep, which led to a fracture — required significantly more time and effort to uncover, with the final accident report taking three years to complete. The collapse led to significant changes in the way bridges in the U.S. are inspected and maintained. The collapsed bridge was replaced by the Silver Memorial Bridge, built as a

cantilever bridge A cantilever bridge is a bridge built using structures that project horizontally into space, supported on only one end (called cantilevers). For small footbridges, the cantilevers may be simple beam (structure), beams; however, large cantilever ...

which was completed in 1969.

History of eyebar-chain bridge construction

At the time of the Silver Bridge construction, eyebar bridges had been built for about 100 years. Such bridges had usually been constructed from redundant bar links, using rows of four to six bars, sometimes using several such chains in parallel. An example can be seen in the Clifton Suspension Bridge, designed by

Isambard Kingdom Brunel Isambard Kingdom Brunel ( ; 9 April 1806 – 15 September 1859) was an English civil engineer and mechanical engineer who is considered "one of the most ingenious and prolific figures in engineering history", "one of the 19th-century engi ...

having chain eyebars that are redundant in two dimensions; this early suspension bridge is still in service. Other bridges of similar design include the earlier road bridge over the

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built by

Thomas Telford Thomas Telford (9 August 1757 – 2 September 1834) was a Scottish civil engineer. After establishing himself as an engineer of road and canal projects in Shropshire, he designed numerous infrastructure projects in his native Scotland, as well ...

in 1826; the Széchenyi Chain Bridge in

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, built in 1839–1849, destroyed in the closing days of

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by retreating Germans in 1945, and rebuilt identically by 1949, with redundant chains and hangers; and the Three Sisters, three self-anchored suspension bridges in

Pittsburgh Pittsburgh ( ) is a city in Allegheny County, Pennsylvania, United States, and its county seat. It is the List of municipalities in Pennsylvania#Municipalities, second-most populous city in Pennsylvania (after Philadelphia) and the List of Un ...

of similar design and construction period (from 1924 to 1928), each with suspension chains consisting of at least eight eyebars per link.

Silver Bridge structure

Low redundancy, high strength

The eyebars in the Silver Bridge offered little to no redundancy, as each chain link consisted of just two eyebars in parallel. (Each bar was 45–55 feet long and 2 inches thick; bars were joined together at the eyeholes using cylindrical pins 11.5 inches in diameter.) These eyebars were made of a new, higher-strength steel (more than twice the tensile strength of other steels of that era), which meant fewer eyebars per link were needed to achieve the required strength to support the bridge (earlier such bridges often used four or more eyebars per link). However, with only two eyebars per link, the failure of one of them would hugely increase the loading on the other, making failure of a suspension chain — and the collapse of the entire bridge — far more likely. Accident investigators found that " d there been three or more eyebars per link, there would have been the possibility that the failure of one bar would not have led to disaster." By comparison, the Brooklyn Bridge used suspension cables made up of thousands of individual wires each to provide the cables a relatively high

safety factor In engineering, a factor of safety (FoS) or safety factor (SF) expresses how much stronger a system is than it needs to be for its specified maximum load. Safety factors are often calculated using detailed analysis because comprehensive testing i ...

of six. Such a cable also has an extremely high level of redundancy, with the failure of a single wire having almost no effect on its overall strength. During the Brooklyn Bridge's construction, it was discovered that some substandard steel wire had been installed in the cables. To compensate, 150 more good steel wires were added to each cable, supplementing each's 5,434 wires. The designer's son, Washington Roebling, decided the safety factor may have been reduced, but remained more than sufficient.

Rocker towers

The two towers that supported the two suspension chains rose nearly from the bridge's main piers. They featured a "rocker" design, which allowed them to tilt slightly at their bases in response to unbalanced loading on the bridge, or to changes in chain length due to temperature change. Prior to their use on the Silver Bridge, rocker towers had been used on a similar bridge in Brazil and, before that, on two large bridges in Europe. Although the rocker towers required the bridge's suspension chains to keep them upright, their ability to tilt allowed the towers to minimize bending stresses — which standard, fixed-base towers must be designed to resist — resulting in a simpler tower design that used less material than fixed towers, and cost significantly less to build. Early into the collapse investigation, the rocker towers provided a significant clue as to the failure's cause and location. Investigators noticed that both towers had fallen during the collapse, a strong indication that a suspension chain had broken — since neither tower could stand upright without the support of intact chains. (The towers themselves showed no sign of failure.) And the fact that ''both'' fell eastward (toward the West Virginia side) clearly indicated a chain break occurring somewhere west of the tower on the western side (i.e., Ohio side) of the bridge. (By contrast, a chain break occurring, say, in the center part of the span would have resulted in the towers falling in ''opposite'' directions, away from each other.)

Design loads

The bridge, which was designed in 1926–27, generally conformed to the engineering standards of its era, according to the investigation into the bridge's collapse, and the investigation's review of the original stress calculations underlying the design found no significant errors. A few years earlier, in 1923, AASHO, a national standards-setting organization, had released documentation to aid engineers in designing bridges — providing quality-control specifications and guidelines on topics such as computing forces and loads, types and properties of steel, and estimating future traffic levels. The bridge's eyebars, which used a new, stronger steel, offered a maximum allowable stress of 50,000

psi Psi, PSI or Ψ may refer to: Alphabetic letters * Psi (Greek) (Ψ or ψ), the twenty-third letter of the Greek alphabet * Psi (Cyrillic), letter of the early Cyrillic alphabet, adopted from Greek Arts and entertainment * "Psi" as an abbreviat ...

, significantly higher than most other steels then in use, and the bridge had a design

of 1.50, within engineering norms. Investigators into the collapse found no indication that the bridge had been overloaded, even on the day it failed. Despite the bridge's age and the heavy traffic on it at the time of its collapse, the load it was carrying was found to be within its normal capacity; and the location where the failure occurred was at less than half the maximum "live" load it was designed to handle when the collapse began.

Victims

According to the Point Pleasant River Museum, a total of 44 of 46 victims were recovered and identified following the collapse of the Silver Bridge. Additionally, 32 vehicles were lost or destroyed.

Recovered victims

* Albert A. Adler, Jr, Gallipolis, OH * J. O. Bennett, Walnut Cove, NC * Leo Blackman, Richmond, VA * Kristye Boggs, Vinton, OH * Margaret Boggs, Vinton, OH * Hilda Byus, Point Pleasant, WV * Kimberly Byus, Point Pleasant, WV * Melvin Cantrell, Gallipolis Ferry, WV * Thomas A. Cantrell, Gallipolis, OH * Donna Jean Casey, Gallipolis, OH * Cecil Counts, Gallipolis Ferry, WV * Horace Cremeans, Route 1, Gallipolis, OH * Harold Cundiff, Winston-Salem, NC * Alonzo Luther Darst, Cheshire, OH * Alma Duff, Point Pleasant, WV * James Hawkins, Westerville, OH * Bobby L. Head, Gallipolis, OH * Forrest Raymond Higley, Bidwell, OH * Alva B. Lane, Route 1, Gallipolis, OH * Thomas "Bus" Howard Lee, Gallipolis, OH * G. H. Mabe, Jamestown, NC * Darlene Mayes, Kanauga, OH * Gerald McMannus, South Point, OH * James Richard Maxwell, Gallipolis, OH * James F. Meadows, Point Pleasant, WV * Timothy Meadows, Point Pleasant, WV * Frederick D. Miller, Gallipolis, OH * Ronnie G. Moore, Gallipolis, OH * Nora Isabelle Nibert, Gallipolis Ferry, WV * Darius E. Northup, Gallipolis Ferry, WV * James O. Pullen, Middleport, OH * Leo "Doc" Sanders, Point Pleasant, WV * Ronald Sims, Gallipolis, OH * Charles T. Smith, Bidwell, OH * Oma Mae Smith, Bidwell, OH * Maxine Sturgeon, Kanauga, OH * Denzil Taylor, Point Pleasant, WV * Glenna Mae Taylor, Point Pleasant, WV * Robert Eugene Towe, Cana, VA * Victor William Turner, Point Pleasant, WV * Marvin Wamsley, Point Pleasant, WV * Lillian Eleanor Wedge, Point Pleasant, WV * Paul D. Wedge, Point Pleasant, WV * James Alfred White, Point Pleasant, WV

Unrecovered Victims

* Kathy Byus, Point Pleasant, WV * Maxine Turner, Point Pleasant, WV

Wreckage analysis

The bridge failure was due to a defect in a single link, known as eyebar 330, on the north of the Ohio subsidiary chain, the first link below the top of the Ohio tower. A small crack was formed through fretting wear at the bearing, and grew through internal corrosion, a problem known as

stress corrosion cracking Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SC ...

. The crack was only about deep when the link failed, breaking in a brittle fashion. When the lower side of the eyebar failed, all the load was transferred to the other side of the eyebar, which then failed by ductile overload. The joint was then held together only by three eyebars, and another slipped off the pin at the center of the bearing, so the chain was completely severed. A collapse of the entire structure was inevitable since all parts of a suspension bridge are in equilibrium with one another. The damage to the link would have been difficult to see during inspection of the bridge:

Inspection prior to construction would not have been able to notice the tiny crack ... the only way to detect the fracture would have been to disassemble the eye-bar. The technology used for inspection at the time was not capable of detecting such cracks.

Aftermath

The collapse focused much-needed attention on the condition of older bridges, leading to intensified inspection protocols and numerous eventual replacements. There were only two bridges built to a similar design, one upstream at St. Marys, West Virginia, and the notably longer Hercílio Luz Bridge at

Florianópolis Florianópolis () is the capital and second largest city of the state of Santa Catarina (state), Santa Catarina, in the South Region, Brazil, South region of Brazil. The city encompasses Santa Catarina Island and surrounding small islands, as we ...

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. The St. Marys bridge was immediately closed to traffic and was demolished by the state in 1971. (A small truss bridge remained to allow access to an island in the river.) The Hi Carpenter Memorial Bridge was later built to replace the demolished bridge. The Hercílio Luz Bridge remained in active service until 1991. Although both it and the Silver Bridge used the same type of high-strength steel for the eyebars, it was built to a higher safety factor than the West Virginia bridge and had greater redundancy, with each suspension chain using an array of four eyebars per link, compared to just two per link for the Silver Bridge. But in 1991, the Florianópolis bridge was closed due to high levels of corrosion. Following extensive renovation, it reopened in December 2019. Modern

non-destructive testing Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), n ...

methods allow some of the older bridges to remain in service, but with tighter weight restrictions. Most heavily used bridges of this type have been replaced with bridges of more modern design. The collapse inspired legislation to ensure that older bridges were regularly inspected and maintained; however, aging infrastructure is still a problem in the United States. In 1983, the Mianus River Bridge in

Greenwich, Connecticut Greenwich ( ) is a New England town, town in southwestern Fairfield County, Connecticut, United States. As of the 2020 United States census, 2020 census, it had a population of 63,518. It is the largest town on Gold Coast (Connecticut), Connectic ...

, collapsed, causing the deaths of three drivers. In 2007, the I-35W Mississippi River bridge disaster in

Minneapolis Minneapolis is a city in Hennepin County, Minnesota, United States, and its county seat. With a population of 429,954 as of the 2020 United States census, 2020 census, it is the state's List of cities in Minnesota, most populous city. Locat ...

, Minnesota, resulted in 13 deaths. In early September 2009, the failure of an eyebar in the San Francisco–Oakland Bay Bridge was discovered during a scheduled closure, resulting in an emergency repair to reinforce the failed member. A memorial was installed in Point Pleasant to commemorate the 46 bridge-collapse victims. A scale model of the original Silver Bridge is on display at the Point Pleasant River Museum. An archive of literature about the bridge is also kept there for public inspection. On the lower ground floor, the museum displayed an eyebar assembly from the original bridge. The museum closed on July 1, 2018, when it received heavy damage due to an attic fire but was later moved to a new building and reopened in 2024. The Silver Bridge exhibit was able to be salvaged. Another eyebar example has been erected for public viewing at a small rest area on the Ohio side of the river, along Route 7. The bridge has been designated as a National Historic Civil Engineering Landmark by the

American Society of Civil Engineers The American Society of Civil Engineers (ASCE) is a tax-exempt professional body founded in 1852 to represent members of the civil engineering profession worldwide. Headquartered in Reston, Virginia, it is the oldest national engineering soci ...

as its collapse ultimately led to the creation of the first national bridge inspection program in the Federal-Aid Highway Act of 1968.

Legacy

Reviewing the collapse and subsequent investigation in his 2012 book ''To Forgive Design: Understanding Failure'', engineering historian Henry Petroski finds it "a cautionary tale for engineers of every kind." As a result of the thoroughness of the investigation, the cause of the disaster was precisely and indisputably found to be "a design that inadvertently made inspection all but impossible and failure all but inevitable. If ever a design was to blame for a failure, this was it." Petroski does not fault the bridge's designers, who were unaware of many of these hazards. Instead, he points to the future. "If there is anything positive about the Silver Bridge failure," he concludes, "it is that its legacy should be to remind engineers to proceed always with the utmost caution, ever mindful of the possible existence of unknown unknowns and the potential consequences of even the smallest design decisions."

In popular culture

In his 1970 book '' Operation Trojan Horse'', and in his 1975 book '' The Mothman Prophecies'', Fortean author John Keel linked the Silver Bridge collapse to alleged sightings of the Mothman. The story was adapted as a film by the same name, released in 2002. Author Jack Matthews wrote a novella, ''Beyond the Bridge'', written as the diary of an imaginary survivor of the disaster starting a new life as a dishwasher in a tiny West Virginia town.

Honky tonk A honky-tonk (also called honkatonk, honkey-tonk, honky tonk, or tonk) is either a bar that provides country music for the entertainment of its patrons or the style of music played in such establishments. It can also refer to the type of piano ...

singer-songwriter and West Virginia native Ray Anderson released "The Silver Bridge Disaster" as the A-side of a 1967 single. Also known as Shane’s bridge. Author James Tynion IV uses both the mothman and the bridge as a plot point in his ongoing comic '' The Department of Truth''. The Silver Bridge was featured as the pilot episode of ''Well There's Your Problem'', then named ''Untitled Engineering Disaster Podcast-like content'', by Justin Roczniak.

Silver Memorial Bridge

The Silver Memorial Bridge is a

that spans the

between Gallipolis, Ohio, and Henderson, West Virginia. The bridge was completed in 1969 as a replacement for the collapsed Silver Bridge, although it is located about downstream (south) of the original.
/ref> The bridge carries US 35 across the river and serves as a major crossing for people and goods traveling between

Charleston, West Virginia Charleston () is the List of capitals in the United States, capital and List of municipalities in West Virginia, most populous city of the U.S. state of West Virginia. It is the county seat of Kanawha County, West Virginia, Kanawha County and ...

, and Southern and Central

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

. The speed limit on the bridge is 65 mph (105 km/h). No toll is imposed at either end. Silver and Point Pleasant Bridges aerial 2019

References

External links

Silver Memorial Bridge
at Bridges & Tunnels.

provides a link to the official state disaster video the next day, archive 1.6 MB wmv file having good quality, no sound: http://www.wvculture.org/history/av/silverbridge256.wmv
Case study of bridge collapseVideo concerning collapse
includes comparison of Silver Bridge and earlier eyebar chain suspension bridges using lower strength materials

at National Institute of Standards and Technology Virtual Museum {{United States bridge disasters Cantilever bridges in the United States Road bridges in West Virginia Monuments and memorials in Ohio Monuments and memorials in West Virginia Bridges completed in 1969 Bridges over the Ohio River Buildings and structures in Mason County, West Virginia Transportation in Mason County, West Virginia Road bridges in Ohio Chain bridges U.S. Route 35 Bridges of the United States Numbered Highway System 1969 establishments in West Virginia 1969 establishments in Ohio Bridge disasters in the United States Bridge disasters caused by engineering error Bridge disasters caused by maintenance error Suspension bridges in West Virginia Suspension bridges in Ohio Bridges completed in 1928 Transportation disasters in Ohio Transportation disasters in West Virginia Buildings and structures in Gallia County, Ohio Transport disasters in 1967 1967 disasters in the United States 1967 in Ohio 1967 in West Virginia Former road bridges in the United States Point Pleasant, West Virginia Steel bridges in the United States 1928 establishments in Ohio 1928 establishments in West Virginia 1967 disestablishments in Ohio 1967 disestablishments in West Virginia Interstate vehicle bridges in the United States Historic Civil Engineering Landmarks