Hoover Dam Bridge
October 14, 2010 by staff
Hoover Dam Bridge, Hoover Dam bypass bridge looks spectacular, stretching 1,900 feet across Black Canyon and 900 feet above the Colorado River churning. Tourists visiting the famous Hoover Dam can not help but turn and take pictures of the new span over.
Well before its completion, it has been called “engineering marvel.”
Perhaps the greatest challenges associated with the long-awaited construction of the bridge linking Arizona and Nevada had less to do with technology and the dimensions of size and more to do with respect for the engineering marvel 1500 feet upstream. That, at least the opinion of a civil engineer highly respected.
“I think the challenge was to bring the standards of the iconic Hoover Dam, to build something in such proximity to a world class structure like this,” said Henry Petroski, a professor of civil engineering at the University Duke. “The engineers involved were very aware of that, they worked with a site that should be respected.”
Although the enormous size and importance of the scope is at the center of photographs, it is always the 75-year-old Hoover Dam attracts tourists away from the glitz and glamor of the strip.
The bridge and 240 million took nine years to move from the drawing board. When it opens to traffic, scheduled for next week, this will be a relief for commuters, travelers and interstate, particularly truckers, who for nine years, took the long way through Laughlin to deliver their goods to Las Vegas. The opening is also eagerly awaited by locals and tourists who are willing to take a view of Hoover Dam, previously available only by helicopter.
Although the bridge is majestic in its own right, he did not steal the limelight from its famous neighbor.
“Bridges like that were built before,” said Bill Bahrenburg, a resident of Long Island, NY, who recently visited the dam with his wife, Coretta. “But the dam was built in 1930, before all this equipment.”
The equipment used to build the largest concrete arch bridge in the Western Hemisphere is obviously much more advanced than what was available for workers during construction of the dam Depression.
But the methods used to establish the bridge have been borrowed from projects dating back to the 1800s, Petroski said. For example, the cable system that was arc 1060 feet of concrete in place on the duration of bypass was the same method adopted by the teams that built the Eads Bridge in Mississippi in 1874.
High-line cranes lifted and moved heavy equipment, columns and blocks of concrete around the canyon are similar to workers in the cable system used to build the Hoover Dam, Petroski said.
“They have certain advantages, they are not using the exact methods they have done to the dam, but they were virtually identical,” said Petroski. “More brutal was used back in the early stages.”
CHOOSING A DESIGN
Petroski acknowledges that construction of the detour bridge was a “world-class challenge” because of the steep canyon walls and rugged terrain. It simply asserts that compliance with the engineering phenomenon that is the Hoover Dam poses greater challenges for engineers.
Dave Zanetell, project manager of the bridge, acknowledged that from the beginning.
“We’re in the shadow of Hoover Dam, he said. “We’re not just building a very difficult project of civil engineering, but we do in the shadow of the largest civil engineering project ever created. It creates a standard heavy responsibilities.”
Aesthetics are vital for communities adjacent to major projects such as bridges. In the Bay of San Francisco, the Golden Gate Bridge is a major destination for tourists worldwide. Thus, when considering to extend its commercial cousin, the San Francisco Bay Bridge, city officials in Oakland have fought for a design that resembles that of the attractiveness of the Golden Gate.
“The deck of Hoover Dam is in the middle of nowhere,” said Petroski. “There is no civic pride so many cities can or can not play the same role. Those who identify with the dam and see it as an engineering marvel, for them it was important how it looks “.
A steel bridge could be a cheaper option for the team of architects responsible for designing the bypass, but he was never seriously considered because of concerns should be far from this historic site. Petroski also said that when the bridge was designed, only eight steel arch bridges are in North America and only five have lasted more than 1,100 feet.
The project management team installed on the concrete bridge, because it is the best compliment of the dam.
Hoover Dam is also an arch structure, so that the arch bridge symmetry offers that might not be obvious to the average observer.
Even the location of the new bridge was discussed. One proposal called for a period of over Lake Mead, but concerns about accidents in road transport of hazardous materials causing them to spill into the water supply in the area set aside that idea.
Building it further downstream of the dam near Davis was considered but ultimately rejected because, among other reasons, the longer detours.
A road very REQUIRED
The federal government has identified a need to improve Highway 93 near the dam 40 years ago. But the project has not started to move forward until the mid-1990s when it was listed as a high priority corridor in the National Highway Designation Act of 1995 and designated a portion North American Free Trade Route.
The road was considered dangerous because of the increasing number of vehicles passing along it and the laces strong as we approach the dam.
Since September 11, 2001 attacks, terrorists, semi-trailers were banned from crossing the dam, instead of traveling nearly 30 miles on their way through Laughlin. Before the restrictions, 14,000 trucks and vehicles crossed the dam each day, according to the Federal Highway Administration.
In early 2005, construction finally began on the detour bridge, which was officially named Mike O’Callaghan-Pat Tillman Memorial Bridge. O’Callaghan is a decorated veteran of the Korean War who served as governor of Nevada from 1971 to 1979. Tillman, who left his pro football career with the Arizona Cardinals to serve as Army Rangers, was killed by friendly fire in Afghanistan.
Since the bridge was built and trucking restrictions on the dam remains in place, commuters would have been happy, they did not have to share the road with semi-trailers, even if the security checks and construction often related to traffic crossing the dam.
But the restrictions affected all consumers in the state, according to Paul Enos, chief executive officer of the Transportation Association of Nevada. Higher fuel and transportation costs have been blamed for rising prices of fruits and vegetables in recent years, Enos said.
“When 90 percent of our manufactured goods come exclusively by truck, then you see an impact,” said Enos. The trip “has absolutely had an impact on our industry.”
“The drivers will take the road which is more efficient in time and money and operations and is the new bridge.”
The bridge is expected to cut about 45 minutes drive to Kingman, Arizona, but with delays that have affected motorists for the past two years, the amount of time saved could actually be more than an hour.
Faster travel times are also expected to open the door to new developments – community room in Las Vegas, Arizona just south of Hoover Dam – should the economy turn around.
As the bridge bypass progress, development companies began marketing the White Hills, just across the border in Arizona, saying that residents of communities near the equestrian Highway 93 could go to the band in one hour.
DO NOT FEAR
It’s no secret that the winds tear the throat. If this was never in doubt, gusts over 50 mph toppled a construction crane high line work on the bridge in 2006.
The bridge is designed to withstand winds of 100 mph.
But the semi-trailers and large vehicles will be prohibited from crossing the bridge when the meters installed on and around the clock span sustained winds of 40 hours mph or gusts up to 50 km / h, according to Mary Martini District Engineer for the Nevada Department of Transportation. The truckers will be notified via numerical restrictions messaging signs posted 100 miles in Utah, California and Arizona, which allows them ample time to choose an alternate route.
Enos said he expected that drivers – and vehicles carrying trailers – will face restrictions on high-wind of about 26 days a year.
Recent tests have shown that the concrete barrier of 54 inches on each side full-bridge protects cars winds. Martini said when gusts pushing against the concrete, they shoot upward, away from traffic.
“Ordinary vehicles will still be able to cross the bridge,” she said. “They will be protected because they are lower than the rail bridge.”
Barriers should also alleviate the anxiety of drivers fear of heights. The guardrails are so high that motorists across the bridge does not even know when they cross the throat, “said Martini.
The guardrails are designed to prevent motorists from slowing curious to take a quick Hoover Dam. To see the dam from the bridge, the driver must exit on the side of Nevada, where a new parking lot and interpretive trail was constructed. Pedestrians can stroll along the upstream side of the bridge, which offers spectacular views of the dam.
“The original design did not go at all,” said Martini. “By adding the width of a bridge is expensive.”
These tourists DAM
Once the detour bridge opened to traffic, Hoover Dam is no longer available on the Arizona side.
Visitors from Arizona to cross the bridge and take the bypass road to the existing visitor center of the dam.
The question is what will happen to the number of visits to Hoover Dam: The dam attracted tourists to appreciate the genius and enjoy the impressive view of Black Canyon? Or are they the dam because it is the main route from Arizona to Las Vegas?
“Hoover Dam was always meant to be a tourist attraction. The minute he got into current government was to sell it as a tourist attraction,” said Dennis McBride, curator of collections and history for the Museum of State of Nevada in Las Vegas. “This will certainly have an impact.
“I think many people got to the dam, seen what traffic is like and just retired and hung around until the light”.
Visitors will be permitted to park in the visitor center or across the Arizona side and park. But it will not be a road. An exit marked from U.S. 93 will guide motorists to the dam on the north side of the bridge.
Going to the dike will be a chore, “said McBride. “I really believe that the number of tourists will decrease People are on the way from here to there;. They will not stop.”
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