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Golden Gate celebrates 75th with help of engineers

The Golden Gate Bridge was heralded as an engineering marvel when it opened in 1937. It was the world’s longest suspension span and had been built across a strait that critics said was too treacherous to be bridged.

But as the iconic span approaches its 75th anniversary over Memorial Day weekend, the generations of engineers who have overseen it all these years say keeping it up and open has been something of a marvel unto itself.

Crews had to install a bracing system after high winds lashed and twisted the span in the 1950s, raising fears it would collapse. Years later, they had to replace vertical cables when they were found to have corroded in the bridge’s damp, foggy climate, potentially destabilizing the span.

The bridge, which rises majestically above a Civil War era fort on the San Francisco side and arches across to the Marin County headlands on the north side, is currently in the midst of a seismic upgrade that has seen many of its key structures replaced or modified. Plans for a moveable barrier to separate north and southbound traffic and a net system to prevent suicides are also moving forward.

“When (one of the bridge’s designers) made his final speech during opening day ceremonies in 1937, he said, ‘I present to you a bridge that will last forever,'” said Daniel Mohn, the bridge’s former chief engineer, who co-authored a book about the span. “What he should have said is, ‘I present to you a bridge that will last forever if properly maintained.'”

The idea for a bridge across the Golden Gate strait, where San Francisco Bay meets the Pacific Ocean, was championed by the engineer Joseph Strauss in the 1920s. Strauss’s original design, submitted to San Francisco city officials in 1921, called for a hybrid cantilever-suspension bridge. The idea for a full-suspension span — the design that was ultimately built — came later.

At a little more than three-fourths of a mile in length, the Golden Gate Bridge would become the world’s longest suspension span.

It had to be light enough to hang from its own cables, but still strong enough to withstand the strait’s fierce winds and the possibility of earthquakes. Some said it was impossible.

Engineers also had to calculate all the potential forces on the bridge without the help of computers.

“In those days, you had (notebooks) and a number two pencil and you wrote it out, did all the math at your desk,” said Kevin Starr, a history professor at the University of Southern California, who has also written about the bridge.

Eleven men died during construction from 1933 to 1937 — ten of them when scaffolding fell through a safety net that had been set up to protect workers.

The conditions were difficult, cold, foggy and windy, and workers who helped construct supports for the south tower had to contend with dangerous tides.

But it was the wind that would continue to vex engineers years after the bridge’s completion. In 1951, it was closed for several hours when wind gusts approached 70 mph and caused the bridge to flutter.

It was twisting so badly, Mohn recalled during a recent phone interview, that the light standards at the center of the span were striking the main cables.

“It sure almost destroyed the Golden Gate Bridge,” he said. The Tacoma Narrows Bridge in Washington — a suspension bridge whose designer also worked on the Golden Gate — had twisted and snapped in about 40 mph winds a little more than a decade earlier. That 1940 collapse was captured on film.

Although the Golden Gate Bridge had stiffening trusses that made it less susceptible to wind, it did sustain damage, Mohn said.

Officials decided to add lateral bracing that made the trusses more stable and reduced the chances of the bridge going into a potentially catastrophic twisting motion.

The bridge would be able to withstand winds of 70 mph today although the goal is to eventually increase its tolerance to 100 mph, according to Ewa Bauer, the bridge’s current chief engineer.

The wind is not the only element to take its toll on the span. The damp, foggy air has also kept its painters and engineers busy.

“You couldn’t have put the bridge in a more corrosive atmosphere than in the middle of the Golden Gate with that salt fog coming in,” Mohn said.

Engineers discovered in the 1970s that the bridge’s suspender ropes — the vertical cables that connect the deck to the main cables — had corroded, some so badly that they could be picked apart with a pocket knife.

The problem in part, Mohn said, was that bridge maintenance had been neglected for many years, particularly during World War II. A design flaw also hastened corrosion.

All of the cables were replaced in the mid-1970s.

There was another scare on the bridge during its 50th anniversary in 1987 when an estimated 300,000 pedestrians gathered on the span, which was closed to vehicle traffic.

The weight of the crowd flattened out the arch of the bridge deck and caused some revelers to suffer motion sickness as the bridge swayed.

Although the bridge supported its heaviest load in 50 years that day, Mohn would later conclude the weight and movement had not exceeded its design capacity.

Today, among the engineers’ most pressing concerns is the potential effect of a major earthquake.

The 1989 Loma Prieta earthquake, which occurred during a live broadcast of the World Series, caused two 50-foot sections of the San Francisco-Oakland Bay Bridge to collapse.

The Golden Gate Bridge was not damaged. But the quake still spurred bridge officials to undertake a massive retrofit of the span — a $660 million project that began in 1997 and is still underway.

Bridge pylons have been reinforced with steel and towers under the bridge’s two approaches were replaced, all while keeping the bridge open and its appearance unchanged. Retrofitting the suspension span is the project’s final phase although experts say its flexibility makes it less vulnerable in an earthquake.

“If I knew when an earthquake was coming, I’d get to the suspension span of the Bay Bridge or the Golden Gate Bridge,” said Abolhassan Astaneh-Asl, an engineering professor at the University of California, Berkeley who studied the Golden Gate Bridge after Loma Prieta. “They are safest places to be.”

The goal is to withstand an 8.1-magnitude earthquake when the retrofit is completed years from now.

The bridge district is also moving forward with plans for a steel net below the span to prevent suicides.

The Golden Gate Bridge has long lured people looking to end their lives. More than 1,200 people have plunged to their deaths from the span since it opened.

The bridge’s board of directors approved the net system in 2008. Funding for the project, which is estimated to cost tens of millions of dollars, has not yet been secured but work on its final design is underway.

The bridge, like other infrastructure, has a lifespan. But Bauer and Mohn say with proper maintenance, the Golden Gate Bridge will endure. The retrofit project alone will buy the span another 150 years, Bauer estimated.

“I believe the bridge was built to absolute great standards of workmanship,” she said on a recent morning at a vista point overlooking the span. “What we are doing right now is repairing…and you can truly do it indefinitely.”
SOURCE: http://www.foxnews.com/us/2012/05/21/golden-gate-celebrates-75th-with-help-engineers/#ixzz1vbw4i0C0

Coastal homeownership has its own challenges

OWNING A home on the coast shouldn’t be a lesson in dreams gone wrong.

For Wayne Higson, the coastal environment offered peace, serenity and a place to get away from it all – until corrosion, wind and water created a nightmare in vacation homeownership.

“People don’t really know how bad things can get until they own a home in this type of environment,” Higson said. “You realize there’s no Yellow Brick Road to follow to get help.”

Higson, 58, of Greenville, N.C., built his dream vacation home in Emerald Isle, N.C., and soon realized the standard construction materials were not faring well in the weather.

He got tired of replacing exterior lighting every few months, and major costs kept creeping up, including repairing the corroded air-conditioning unit.

“Most people don’t know it, but water can run uphill on the Outer Banks,” he said. “Those high winds and water in every direction mean it has to go somewhere.”

For his years of hassle, hardships and heartache, Higson documented his efforts in a recently published book, “Coastal Homeowners: The Complete Photo Guide to Coastal Maintenance” (DWH Publishing LLC, 2011).

The book has more than 300 color photos, each illustrating problems and solutions that promise to help save time and money. Chapter highlights include hardware fasteners and nails, doors and windows, exterior siding and trim, winterizing coastal homes and hurricane preparedness.

“People have to remember that no matter how pretty the day is outside, the weather is taking a toll on their house,” Higson said. “The best thing to do is be prepared and know how to handle maintenance.”

Higson, a general contractor, started his quest in 1992 when he built his vacation home. For more than 10 years he collected information and 4,000-plus photos documenting his work.

“You can go to the store and buy a toaster that comes with directions in different languages, but if you buy a million-dollar home, you are on your own,” Higson said. “That’s just not right.”

In addition to advice and helpful tips, Higson also created a list of 110 manufacturers who sell, use or create coastal-friendly products. Their contact information is included.

“It’s so important to address these issues before they become a problem,” said Dave Barber, who works with Carolina Casual Furniture in Point Harbor and Kellogg Supply in Manteo, both on the Outer Banks, and owns Willington Grill Co.. “Rust is what kills a grill. If people know that before they buy, then they can choose a superior product. This book will help homeowners be better informed.”

Higson said he is already working on a second edition. He has taken more photos and logged different problems that he hopes to highlight.

SOURCE: http://hamptonroads.com/2012/04/coastal-homeownership-has-its-own-challenges

Big Dig needs $54 light fix – corroded tunnel fittings must be replaced

The state’s top highway official says all the light fixtures in the Big Dig tunnels must be replaced, a $54 million effort made necessary by design or manufacturing defects that have led to dangerous corrosion.

The project, expected to begin next year, will cause frequent lane closings in the tunnels for up to two years, a headache for motorists. The work will be done largely at night, with traffic diverted to surface roads.

Since a light fixture fell onto the northbound lane of the Thomas P. O’Neill Jr. Tunnel in February 2011, engineers have temporarily shored up the 8-foot light fixtures in the 7.5 mile tunnel system with plastic ties. Now, after a year of study, the state’s highway administrator, Frank DePaola, is recommending a complete overhaul, the most expensive of several alternatives.

“The preferred alternative is a complete replacement,’’ DePaola told the Massachusetts Department of Transportation board of directors Wednesday.

“The existing fixtures continue to corrode,’’ he said. “We could have more incidents. For that reason, I think it is best for all of us that we remove the fixtures.’’

“We just have to do it,’’ added Richard A. Davey, the state transportation secretary and DePaola’s boss, agreeing it is a safety issue.

Though the replacement project will be expensive, DePaola said the new fixtures offer opportunities for savings over the long term from energy efficiency. He said the more energy-efficient LED lights are expected to cost $2.5 million a year less in electric bills than the current fluorescent lights.

He also said the new fixtures will not be susceptible to the moisture that apparently caused the corrosion in the existing fixtures. The new light casings will be sealed plastic fixtures, rather than an assembly of removable component parts that require maintenance. When the new lights burn out, the entire fixture will be replaced, he said.

Money for the overhaul is expected to be drawn from a maintenance fund set up in 2008 with the proceeds from a nearly $500 million settlement with Big Dig contractors Bechtel/Parsons Brinckerhoff and others for shoddy work on the $15 billion project, which has been plagued by problems ranging from water leaks to a fatal ceiling collapse in 2006.

Before the state can begin the project, however, the transportation board must approve the plan. In addition, the federal government must approve use of the Big Dig settlement fund for the light replacement project.

Transportation officials still have not determined who is to blame for the corrosion that so weakened one fixture that it fell and left dozens of others badly compromised, DePaola said. They initially focused on the company that manufactured the lights, NuArt of California, but the company was bought out by another firm and discontinued years ago.

“We are working with our attorneys and engineering consultants to determine responsibility,’’ DePaola said, adding, “You can’t get damages from a company out of business.’’

If the state is able to recover damages, that money will be used to replenish the maintenance fund, which now has a balance of about $393 million, he said.

If the lighting plan is approved, as expected, tunnel closings related to the overhaul could begin in about a year, transportation officials said. Crews will close either the northbound or southbound side of the O’Neill Tunnel at 11 p.m. and reopen it at 6 a.m.

Closings will also be necessary at the Ted Williams and Interstate 90 Connector tunnels.

Such closings, however, have already begun in the O’Neill Tunnel for washing and other maintenance and will continue for about a year, transportation officials said.

Wednesday’s announcement caps a turbulent year in Big Dig history as issues related to water in the tunnels forced out several top state transportation officials.

The Globe reported last year that the Big Dig’s chief engineer, Helmut Ernst, wrote in a memo to his bosses that constant water leaks in the tunnels were causing safety problems and at least $150 million in damage, including corroded electrical systems and flooded air vents, and even damage to the enormous steel girders that support the O’Neill Tunnel.

In his memo, Ernst wrote that “leaks greatly contribute to the moist corrosive tunnel environment,’’ especially when combined with road salt.

But Ernst attributed the fallen light to a much larger problem: the salty ground water that seeps in through cracks and other openings in the tunnels.

However, Ernst was fired in August after saying publicly that Big Dig engineers tried to avoid putting into writing discussions of problems in the tunnels. In fact, Ernst’s team of engineers filed no reports on the light fixture collapse after it happened.

On Wednesday, DePaola acknowledged leaks as an ongoing and permanent issue.

“We continue to work on the leaks,’’ DePaola said. “I think we are slowly reducing the amount of leaks in the tunnel, but there will always be some infiltration. And we will always be dealing with sealing off leaks.’’

SOURCE: http://www.boston.com/news/local/massachusetts/articles/2012/04/05/big_dig_tunnels_need_54m_light_replacement_mass_officials_say/?page=1