As the Soviet Union fell, so did the final obstacle to perhaps the ultimate civil-engineering project.
BY GREGORY T. POPE; PM Illustration by Alan Gutierrez
Big bridges are back.
After years of focusing innovation on the short span, civil engineers again have far-reaching ideas in the blueprints.
By the year 2000, the title of world's longest single span will have jumped from England's Humber Estuary to Scandinavia's Great Belt to Japan's Akashi Kaikyo Bridge, with its 6528-ft. main crossing.
And even longer bridges loom on the horizon. Sicily to Italy? Spain to Africa? Today, neither seems too much of a stretch.
But to one maverick engineer, a final gap still beckons. It's the gap between East and West, between two worlds closer now than they have been in decades.
It's a gap across time as well as space, because it spans the international date line. By geographic standards it's trivial--about 55 miles--but by engineering standards it's an ocean to cross.
It's the Bering Strait. T.Y. Lin wants to bridge it.
Preposterous? Not so fast. Lin is no crackpot. Yes, he's daring, but he's also a decorated engineer, with the President's National Medal of Science among many honors under his belt.
He's written top texts on concrete construction, designed dozens of groundbreaking structures, taught at the University of California at Berkeley for 30 years--in short, enjoyed a glorious 6-decade career in civil engineering.
But the Alaska-Siberia crossing--which Lin has dubbed the Intercontinental Peace Bridge--has been this man's dream for 25 years. In 1969, he founded a charitable organization to finance feasibility studies.
In 1986, he nonplused Ronald Reagan by handing him Peace Bridge construction plans after the president had spoken fervently on the Strategic Defense Initiative.
And in 1994, as Russia reaches out to the West, the Peace Bridge has returned in a new incarnation.
Only this time it's no longer just about peace. It's about oil.
Lin and Philip Chow blueprinted Gibraltar bridge with hybrid cable-stayed/suspension design. Each span would run more than 3 miles.
That's because the attention of petroleum companies is shifting toward Krasnoyarsk, Irkutsk, Yakut--the vast, unexplored eastern stretches of Siberia.
Already, Japan and South Korea are considering pipelines to siphon natural gas out of the region. Supplies there could dwarf the current exports into Western Europe:
Last summer, geologists at Russia's Academy of Sciences prophesied that quadrillions of cubic feet of natural gas and billions of barrels of oil await exploitation in Siberia's hinterland.
This potential bonanza may just provide the financial underpinnings of the Peace Bridge. Lin wants to leverage construction by running oil and gas pipelines below the bridge's roadbed.
"I've switched to an economic front," he says. "You see, the bridge will cost a few billion dollars. The road on both sides will cost $50 billion.
The petroleum resources are worth trillions of dollars. But to get to the oil and gas you need roads. And you need the pipeline."
Laying the economic groundwork for the Peace Bridge will probably be harder than building the structure itself. In Lin's scheme, the bridge practically rolls off an assembly line in modules.
A total of 220 spans--each a double cantilever, stayed by two pairs of heavy-duty steel cables--march across the strait, the sequence hooking slightly north at the Diomede Islands.
Think the Bering Strait connection is a bridge too far?
How about a tunnel instead? That's the proposal of California architect Stuart Resor--in fact, it's the linchpin of a globe-spanning railroad called World Link.
Trains race through World Link tunnel made from prefab double-tube segments.
Resor's concept calls for an elevated track from Washington, D.C., to Paris through "the world's backdoor--swinging up through Canada, diving below the Bering Strait and arcing across Russia and Europe.
The 300-mph needle-nose trains would run on side-mounted wheels locked into grooved channels.
For the sub-strait tunnel, Resor would adopt the procedure now under way at the Central Artery tunnel project in Boston Harbor.
Prefabricated steel-tube sections are sheathed in concrete, lowered into trenches, pumped dry, buried with rubble and gasketed together.
The # 1 reason for NATF & GATT Trade Agreement for the USA is, Oil to Fuel America into the Future!
As with the Peace Bridge, the quest for oil would fuel construction of Resor's tunnel. But Resor also envisions a day when ebbing petroleum supplies will render airline travel too costly.
"There won't be any easy solution replacing aviation fuel for the long-distance haul," he predicts. Further justification, in Resor's view, for WorldLink.--G.T.P.
Every unit crosses a modest 1200 ft., except for two 1800-ft. spans for the major navigation channels east and west of the islands. The deck consists of a double box.
While road traffic rumbles across the top face in summer months, the upper box accommodates an all-weather twin-track railroad, and the lower box provides space for pipelines.
Drawing from offshore oil-rig techniques, Lin rests this modular superstructure on a series of concrete gravity piers, curved like fat bugles to fend off marauding ice floes.
Each of these is towed to its position, sunk onto a base raft and weighed down with ballast.
Then a huge catamaran barge floats each span to its pier.
The waters themselves offer little challenge--the strait runs no deeper than 180 ft.--but as in all Arctic construction, timing is critical: Weather restricts activity to only five months out of the year.
And because of the climate, concrete must swaddle everything, even the cables. "That's important from two points of view," explains Lin. "Number one, the concrete protects the steel. It simplifies maintenance in an icy area.
Number two, it stiffens the bridge, so it's not just hanging from rope." Only at the deck's expansion joints would steel--coated to resist rust--see daylight.
The Peace Bridge is typical of Lin's designs: At first glance they fly in the face of logic, but eventually they fly.
Case in point: an award-winning proposal for a bridge across the Strait of Gibraltar, linking Spain and Morocco. Lin and colleague Philip Chow picked an 8.75-mile route that European engineers had written off because it crossed water too deep.
The Lin solution: straddling the depths with two enormous main spans that leap 16,000 ft., made possible by cable-stayed cantilevered struts that trim each suspended length to 9842 ft.--still a record span, but within reach of current technology.
Only time will tell if the Intercontinental Peace Bridge gains similar acceptance, or if fortune leads two nations to forge this link.
If so, then the bridge will redefine not only geopolitical boundaries, but also the boundaries of civil engineering.