Engineers on a Dare—Building a Bridge Near the World’s Strongest Quake

November 10, 2016 | Comments

bridge001In an artist’s depiction, the Chacao Channel bridge connects the island of Chiloe and mainland Chile. If finished, it will be the longest suspension bridge in South America. Its daring design won it the “Bridge” category at Bentley’s Year in Infrastructure 2016.

How do you build a bridge near the site of the strongest earthquake ever recorded? Very carefully, says Matias Valenzuela, from the Ministerio Obras Públicas de Chile, who is presenting on what could be the longest suspension bridge (2,750 meters) in South America. The plans for the bridge won the “Bridge” category in Bentley’s Year in Infrastructure 2016 in London.

A 9.5 earthquake rocked Chile in 1960, killing 1,655 people, injuring thousands and making 2 million people homeless, according to the United States Geological Survey. To this day, the Chile quake remains the strongest one ever recorded.

The experience of the world’s worst quake may have prevented even the thought of connecting the island with anything but ferries. The bridge will also be battered with high winds as well as the ocean currents that abound in the many deep fjords along Chile’s coastline.

But engineers are not ones to give up so easily. After all, what is building a bridge compared to putting men on the moon?

“We had to switch from a cable stayed design to a suspension design,” said Valenzuela, “to withstand the seismic demands in the area.” A suspension bridge can sway with, rather than try to resist, nature’s forces.

After all, San Franciscans who live in fear of the “Big One” are fond of saying the safest place in the entire city is on its Golden Gate Bridge.

 

Why Build It?

The bridge will be a boon to the populations on either end of the bridge, small as they are. A round trip to the mainland will only take a few minutes—with access to a car—compared to 20 to 45 minutes on the ferry. The village of Chacao can be now connected with Ancud, the 2nd largest city in the Chiloe province with a population of 40,000.

People on both sides will owe a debt of gratitude—and maybe more—to a 2009 multinational effort that was needed to revive plans for the bridge. The effort sought out and found funding from various donors, such as Brazil, France, Norway (a nation of fjords) and South Korea.

The cost of the bridge was originally to be capped at USD $740 million, according to the Chilean authorities. The bridge was to have been named the Bicentennial Bridge in honor of the country’s birthday, which came and went in 2010.

However, the completion of the earthquake-defying bridge remains a dream of engineers at the time of this writing. A local news source reported in March 2016 that a “massive delay” could stall the laying of the foundation by 10 months, citing engineering and administrative issues.

Valenzuela, encouraged by honors received at the Bentley event, expects construction to start in 2017 and for it to be finished by 2020.

Should the Chacao Channel bridge come to pass, there may be may others raising their hands and saying, “Me too.” After all, Chile’s 2,500-mile coastline is dotted with over 5,000 rocky islands—most of them lacking bridges.

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