What happened to Tacoma Narrows Bridge?
on 7. November 1940 was a big news of the day of the overall failure and collapse of the Tacoma Narrows bridge in Washington. The bridge simply torn and fell into the water Sound. How and why this happened are questions that have only recently been answered. The bridge across Narrows meant that the state government could open another part of the state for expansion, so they wanted to build one. Architects and engineers were looking for the most beautiful and lightest weight and thinnest patterns. As a result, Tacoma Narrows, when he was finished, was 5,939 feet long (1,810.2 meters) and 39 feet (11.9 meters). It was also light, due to shallow nasal nose used in construction. Elegant? Undoubtedly. Open for operation 1 July 1940.
The public did not know that the bridge showed some unusual behavior in the construction stage, but soon they were given a hint that everything was not well with their high, spindle bridge. ODBThe sculptures noticed unusual linear movement along the road when the wind grew, how often it does through the snippets. The engineers tried to compensate for some of this "oscillation" by installing hydraulic buffers and steel "bound" cables to stabilize. Yet, the central range was customary up and down, similar to the roller coaster.
The drivers soon found out that the cars would disappear in front of them in the "valleys", reappearing on the ridge of the hill. People came from far wide to go on the bridge of roller coaster. The locals quickly nicknamed the structure of "Galloping Gertie" and stuck.
on 7. November 1940, the State Police of the Highway Department closed the bridge for operation about 10:00, after reports of 3 to 5 feet (1 to 1.5 meters) were reported, with winds exceeding 35 mph (56.3 km / h). Fortunately, there was still only one person and managed to get off before the central range collapsed. When the crowd of the Assembly was watched by fascinated horror, the central range ofALO circle from side to side and also moved up and down. Anyone who watched knew that the bridge could not resist this kind of movement for a long time.
At about 10:30 in the morning, the first pieces of the pavement began to fall. At 11:02, the cables holding the central range began to retreat and the western part turned over and crashed into the water. Until 11:09, the remaining part of the central range was also gone. Galling Gertie was no longer. Only the side span and towers remained.
So the question was chased by engineers: What happened to their bridge? The article of this scope cannot explore all physics and aerzúti with the questions of osynamics, but the first hypothesis believed that the resonance of the wind destroyed it. Later testing and engineering models showed that this was probably not the case.
In fact, the failure of the Tacoma Narrows bridge was a combination of many factors, including design shortcomings. Used shallow boards of beams to reduce weight instead of deep open stiff products, causing a bridgeLess stable. The structure was also quite simply too long to its width. The wider bridge could survive, but the road was too narrow to withstand others.
Aerodynamics and a strange sounding phenomenon called "self -expression" also played a role. When the span began to curl and was more unstable, instability brought instability. Therefore, when the span started its twisted movement, he also fed the flames of instability until the structure failed. "Self-Excitation" means that one thing leads to the other and turns back to each other until we are threatened. Gertie's collapse is available online, as well as pictures of undulating, twisted roads. Many articles, also online, can also view more answers to the question "Why".
World War I and the resulting deficiency of the steel delayed construction of another Tacoma Narrows bridge. The second range of steel cable suspension varieties opened on October 14, 1950. This time engineers studied and modeled patterns for four years to complete their elections. OneE is not threatened. As a toll bridge, it has paid for itself and currently contains the fifth longest range in North America.
Galling Gertie costs Washington millions of dollars, but its failure revolutionized the profession of bridge building. Proposals are now undergoing strict testing and modeling before they are sometimes built, saving money and human lives.