The Silver Bridge was a 1928 eyebar-chain suspension bridge called after the color of its aluminum paint. The failure of a single eyebar in a suspension chain owing to a minor 0.1 inch (2.5 mm) deep fault was determined by an investigation of the debris. This single, critical element prevented the remaining links from functioning as intended, and the bridge collapsed into the Ohio River.
The cause of the single eyebar's failure has never been fully explained but may have resulted from corrosion due to exposure to river water. Other factors such as stress caused by traffic may also have contributed to the failure.
The accident occurred on February 14, 1955, when a truck crossing the bridge failed to lower its load of steel rails before entering the highway lane. The driver stopped the vehicle in time but not in time enough to avoid hitting another truck crossing in the opposite direction. This second truck then hit the first causing it to overturn onto its side, dragging down the bridge until it collapsed under the weight of both trucks and their loads. No one was killed but there were three people in the other vehicle who suffered only minor injuries.
After the crash, investigators found that the eyebar had a slight bend in it. Corrosion was believed to be the cause because even though the eyelet was only 0.1 inches (2.5 mm) deep, it had rusted through completely around its circumference.
The Silver Bridge collapsed under the weight of rush-hour traffic on December 15, 1967, killing 46 persons. Two of the victims' bodies were never discovered. The accident resulted in one of the nation's first multistate disasters.
On November 1, 1967, the day before the collapse, the New York State Department of Transportation performed a safety inspection of the bridge and found it to be in good condition. The following day at about 2:30 p.m., as thousands of vehicles crossed the bridge into Pennsylvania, another state department of transportation inspector noticed that one of the bridge's center spans was swaying back and forth. He reported his observation by telephone to the district office in Pittsburgh but was told there was no need for concern since the bridge had been inspected recently and was in good shape.
About four hours later, at 8:20 p.m., the last vehicle crossed the bridge and it began to tremble violently. Within minutes, it collapsed into the Ohio River below. The cause of the accident was determined to be overloading. The bridge was carrying too much traffic at once, which caused it to become unstable.
There were two separate investigations into the cause of the accident. The National Transportation Safety Board concluded that the primary factor leading up to the collapse was excessive traffic load.
The Silver Bridge was the first eye-bar suspension bridge to be built in the United States. The bridge's eye-bars were chained together in pairs. A massive pin ran through the eye, connecting one piece to the next. Each chain link was made up of two 2" x 12" bars joined by an 11" pin. The bridge was painted gray.
The Silver Bridge was completed in 1913 over the Ohio River near Wheeling, West Virginia. At the time it was the longest suspension bridge in the world. The main span was 1,595 feet long while the tower was 370 feet high. It weighed about 740 tons and had 28 cross-members to support its weight.
The bridge was named for its silver color caused by the oxidation of its iron components. Iron oxide is also known as rust. Before construction began, some people thought the bridge would collapse under its own weight because it was so tall.
In 1967, after many years of use, the New York City bridge that was then known as the Brooklyn-Queens Expressway collapsed due to rust damage from heavy traffic. This incident spurred government agencies to search for a way to prevent bridges from deteriorating with age or abuse. The solution was developed by the National Academy of Sciences' Institute of Medicine and was adopted by the American Society of Civil Engineers as standard practice for designing new bridges. This system is called "Static Renewal."
Steel The Silver Bridge was the first in the country to employ a "eyebar link" suspension system. The eyebars were two inches thick and resembled huge automotive wrenches. They were placed about every other foot on the bridge, each one carrying four vertical strands of wire that were then connected to the horizontal cross-members of the structure.
The system was invented by George Selick, who also designed the undercarriage for the Ford Tri-Motor airplane. It was an improvement on traditional truss bridges, which are made up of straight, evenly spaced wooden beams. The eyebars reduced the amount of material needed for the bridge and increased its strength while at the same time making it less likely that it would collapse under its own weight or that of vehicles crossing it.
Selick's invention won him a patent in 1905. But it wasn't until after his death in 1919 that the bridge itself became famous as the site where both sides of the controversy over its construction ended up facing each other across it.
People often ask me where the name "Silver Bridge" comes from. It's based on the fact that when it was constructed, many people believed it would be made of solid silver. The idea for such a magnificent bridge came from Henry Ford, who wanted to create a vehicle that would be able to run without breaking down.