Earthquake could destroy 520 bridge, too, study says

An Article By LARRY LANGE

So you thought the Alaskan Way Viaduct was on shaky ground? Now you can worry about the state Route 520 bridge, too.

A recent engineering analysis, quietly discussed among state transportation officials and planners, says a magnitude-6.5 earthquake in the wrong spot could take out both structures.

The analysis says the viaduct fronting Elliott Bay and the bridge crossing Lake Washington have about the same ability to withstand the kind of major earthquake that occurs on average every 210 years. It is widely accepted that this region is at risk of catastrophic quakes.

To put it bluntly, a quake ranging in magnitude from 6.5 to 7.2, located close to the Earth's surface and near the spans, could destroy either structure or both.

The odds of this actually occurring have not been determined, state bridge engineer Patrick Clarke said.

Last year's major earthquake, centered near Olympia, registered a magnitude 6.8 but was centered 35 miles underground and 60 miles to the south -- too far away to destroy either span. Still, it was forceful enough to damage both, and to close the viaduct for several days for inspections and repairs.

Losing the bridge and viaduct, besides being deadly, could cripple traffic for years.

More than 225,000 drivers now use the two bridges every day, and would be forced to use side streets or other already-strained highways.

Rush-hour traffic backups could routinely extend south on Interstate 5 as far as the Boeing Access Road or east on Interstate 90 as far as Interstate 405, said Morgan Balogh, the state's regional traffic operations engineer.

"It gets ugly in a hurry, I'm sure," said Les Rubstello, manager of the state's Trans-Lake Washington study examining ways to improve mobility in the 520 corridor.

Replacing the 520 bridge could cost from $1.8 billion for four lanes to $7.4 billion for eight lanes, according to recent state estimates. Construction, depending on the option chosen, could last from nine to 11 years.

That the 520 bridge is as quake-vulnerable as the viaduct was startling news to some.

It was "new information for me," said King County Councilman Dwight Pelz, chairman of the council's Transportation Committee and a key player in planning a regional ballot measure to pay for major highway and transit improvements.

The quake analysis actually has been around for several months and was known to state officials and to some members of an advisory committee discussing whether to rebuild or replace 520's Evergreen Point Bridge.

Rubstello said the state didn't formally release details to avoid sounding "like we were crying wolf twice" after much-publicized reports about the viaduct's vulnerability to tremors.

In February, state Transportation Secretary Doug MacDonald urged legislators and Gov. Gary Locke to set aside money to plan replacements for both the viaduct and 520 bridge.

The letter did not mention the earthquake risk but said the 520 bridge is vulnerable to high winds and waves, which could break it apart.

"I've been flapping my lips at every meeting that it's an unsafe facility," said Redmond Mayor Rosemarie Ives. "Nobody wants to listen."

The quake analysis "serves to move 520 (replacement) up on the regional priority list," Pelz said.

Doing this, however, could reignite controversies about the effects of a bigger new bridge on the shorelines it connects. And some, including transit advocate Peter Hurley, want to see more detailed information before they agree that replacing the bridge makes more financial sense than retrofitting it to better resist earthquakes.

Engineers have long said that a major quake could fatally damage the viaduct, a 2.2-mile, double-deck structure that carries state Route 99 along the Seattle waterfront from the port docks to Aurora Avenue.

They have said the viaduct, which carries about 110,000 vehicles on an average weekday, could collapse if ground gives way under part of it, or if concrete cracks and support columns shear.

In a report issued a year ago, a team of engineers recommended replacing the viaduct, saying retrofitting it to meet modern earthquake standards didn't make sense.

That report came four months after an earthquake did more than $1.7 million in damage to the viaduct, cracking it and prompting crews to close parts of it for several days while it was shored up.

The same Feb. 28, 2001, earthquake that opened cracks in the viaduct did minor damage to the 520 bridge, loosening bolts in a joint on the western approach span.

A 1993 earthquake-evaluation study concluded that the tops of the 520 bridge's approach supports near each shoreline, filled with concrete five feet down from the top, would bend enough in an earthquake to hold up.

But that's no longer accepted. Below those solid "caps," the supports are hollow shells with 5-inch outer walls. State officials said researchers in California later became skeptical about how well hollow columns would hold up.

After a tug and barge hit and shattered one of the 520 bridge columns two years ago, Washington state engineers re-evaluated the earlier conclusion.

And in a memo three months ago, two state engineers said the caps wouldn't bend enough in an earthquake to keep the bridge supported.

That conclusion also was included in a brief internal state Transportation Department report in January. This said that even though the double-deck viaduct and the floating 520 bridge are built differently, the earthquake risks to the two structures when faced with the 210-year earthquake "are almost identical."

Rubstello said state analysts are just beginning to calculate how motorists would react to the simultaneous loss of both structures. Balogh, the state engineer, said backups would be longer on I-5 and I-90 and congestion would worsen on other highways as drivers tried to compensate for the loss of the two spans.

"You're not going to sit on the freeway for an hour. You're going to risk it on an arterial" (street), he said.

Some think the earthquake risk makes the 520 bridge a higher replacement priority. State officials have said retrofitting the 520 bridge for safety is not worthwhile because of its age, though they did do $1.14 million in retrofitting work in 1999.

Even people in Seattle's Montlake neighborhood, where the bridge's west approach is located, agree it should be replaced, said Jonathan Dubman, president of Montlake Community Club.

But the question is: With what? The advisory committee hasn't decided how many lanes a new span should have. That's a big issue in Dubman's neighborhood where, depending on the width of a new bridge, people living 200 feet from it now "could be as close as 20 feet to the new highway."

"The neighborhood would support an effective transportation solution that would improve the quality of life along the (520) corridor and through the region," Dubman said. "But we have some work to do to figure out a solution."

Dubai's Mile-Long Super Arch Bridge

Dubai is going ahead with another ambitious project which is a super arch bridge. Dubai's next super structure will stand higher than the George Washington Bridge (604 ft.) but fall short of San Francisco's existing Golden Gate Bridge (746 ft.).

100 Years Bridge Oberndorf - Laufen

Bridge construction has gone back along way in history

Oberndorf has witnessed a large number of devastating floods during the last centuries. The first record of a bridge being washed away dates back to 1316. The damage was often caused by flotsam which was caught between the wooden bridge pylons and forced the water to dam up. Ultimately the bridges were often just washed away. During the last decade of the 19th century four floods cased great damage, and a decision was made to relocate the town to a more elevated plateau.

The Bavarian Laufen and Austrian Oberndorf developed the plan to construct a stable bridge made of stone and iron incorporating a greater span. As the bridge was in close proximity to both the old town square of Laufen and the new centre of Oberndort, an aesthetic design was implemented.
The two-pylon construction had three apertures, the largest of which was on the Austrian side to allow for shipping needs. The construction was made of 648 tonnes of Martin River iron ore, with a chain-like curved upper cable and a straight lower cable. The facing of the pillars and decorative elements required an additional 67 tonnes of material to ensure a pleasing design. Eagles with spread wings were placed upon the bridge portals, adding to the elegant impression of the construction. The bridge was inaugurated on the 2nd of June 1903 in a collective festival of inhabitants from Laufen and Oberndorf.

Sungai Johor Bridge

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The Sungai Johor Bridge will definitely be the longest cable stayed bridge in Malaysia

The cable-stayed bridge has a single central plane of cables in a harp configuration.

Construction of the cable-stayed bridge across the Johor River began in 2006; the bridge was first planned in 1996 but the Asian currency crisis put paid to it at the time. The bridge will connect Kong Kong on the western bank to Teluk Sengat in the east.

The preliminary and detailed design and engineering work was carried out by COWI Consulting Engineers and Planners AS and Ranhill Consulting Sdn Bhd for Senai Desaru Expressway Berhad (the concession holder). Three Ranhill engineers spent six months in Denmark with COWI designers to develop the design of the bridge.

The construction was undertaken by Ranhill Engineers and Constructors Sdn Bhd, foundations were constructed by Ranhill Antara Koh Sdn Bhd, the steel construction was the remit of Jawala and MBEC. Waiko Engineering Sdn Bhd are construction subcontractors, the stay cables and incremental launching of sections were contracted to VSL International.

"The new road will be a four-lane dual carriageway and will improve access across the region of Johfor."

BRIDGE STRUCTURE

The main span of the bridge is 500m and the pylon height is 150m above the surface of the river. The cable-stayed design of the bridge is in a harp configuration but in a single central plane (only one set of stay cables). This means that the cables are in a near-parallel arrangement, by virtue of the fact that the cables are attached to various points on each of the two ‘A’ shaped concrete pylon towers.

Each tower has a foundation of 34-bore 2m-diameter steel cased piles. The result of this is that the height of attachment of each cable on the tower is similar to the distance from the tower along the roadway to its lower attachment.

The middle 739m of the bridge has a composite deck with a 250mm-thick precast concrete deck slab and a closed structural steel skirt (3.5m deep). There are two 484.5m deck sections on either side of the central section and these consist of a concrete box girder structure.

Millau Viaduct – World's Tallest Bridge

Extreme Engineering Marvel

Mankind has certainly moved on to the next challenge of constructing on what was thought to be as the impossible by our predecessors. Credits to the Engineers.

To me there are few things more impressive than being on a man-made structure, such as a very tall building or a bridge, and viewing blue sky above and clouds below. Of, course for this to occur the structure has be be rather high and the clouds low.

This is why I was immediately impressed when a friend sent me pictures of the Millau Viaduct, which crosses the valley of the Tarn River valley near the city of Millau in the mountains of southern France.

Normally it is the high mountains that present a challenge to engineers building roads that connect two or more points. However, in case of the Millau Viaduct, the mountain area through which the A75 autoroute, also known as la Méridienne, passes is apparently rather high most of the way until it reaches the Tarn River valley.

Bridge with blue sky above and clouds below.

Bridge spans valley of the Tarn River.

 

A Joint Franco-British Project

As can be seen from the picture at the right, one has to traverse a long, winding road down the mountain on one side of the valley and then immediately repeat the process while climbing up the mountain on the other side of the valley.

In addition to the kilometers / miles and time added by the trip down into the valley and back up into the mountains, time was also lost in the past to traffic congestion in the town and on the two lane bridge across the Tarn River. It is estimated that the bridge over the valley has shortened the driving distance between the Paris and the Mediterranean coast of France by 100 kilometers (about 62 miles) and, during the summer tourist season, reduced travel time by as much as four hours.

Construction of the bridge was a joint Franco-British project with help from companies in other European countries. Financing for the 394 million Euro (U.S. $524) project was provided by the French construction firm Eiffage. As a result of corporate mergers*, the Eiffage frim includes the firm that built the Eiffel Tower in Paris which, at the time of its completion in 1887, was the tallest structure in the world. This is obviously a company with long experience in being involved with construction of structures of record setting size. British architect Norman Foster designed the bridge, which has come to be viewed both as a work of art as well as a construction marvel, while the French bridge engineer, Dr. Michel Virlogeux, provided the engineering design.

While planning began in the late twentieth century, actual construction did not begin until December 2001 and its 2005 target completion date was achieved a little early when it was formally dedicated on December 14, 2004 and opened to traffic on December 16, 2004.

The Millau Viaduct is an artistic and engineering marvel. It currently holds the record for having the highest piles (the pilers rising from the ground and supporting the bridge from below) of any bridge in the world with its highest being 244.96 meters (803.7 feet) and the highest mast (the pilers rising up from the top of the bridge and holding the suspension cables) which towers 343 meters (1,125 feet) above the roadbed of the bridge. It also has a claim to having the highest roadbed of any bridge in the world with its roadbed reaching 270 meters (885.8 feet) above the river below.

However, the roadbed of the Royal Gorge Bridge in Colorado in the United States tops this with its roadbed which towers 1,053 feet (321 meters) above the river below. Based upon height of roadbed, the Royal Gorge Bridge is the highest in the world while based upon mast height, the Millau Viaduct is the highest in the world. Regardless of which is the highest, the Millau Viaduct is the clear winner in terms of length and beauty.