June 2013
CONSTRUCTION WORLD
47
A diamond-shaped cathedral of concrete and finely
tuned steel, the Rio Negro Bridge rises from the
Amazon jungle to span one of the world’s largest
rivers. A massively complex project, the Rio Negro
bridge measures 3 500 m in total length, and boasts
a 400 m long cable-supported central section which
will allow the Amazon’s significant shipping traffic to
pass unimpeded.
roads & bridges
WHEN COMPLETED, THE BRIDGE
over
Rio Negro will be the second largest cable-
stayed bridge over freshwater on the planet,
second only to the crossing of the Orinoco in
Venezuela at Ciudad Bolivar. The new bridge
will reduce the trip from the regional capital,
Manaus, to the interior of the Amazon by 30
minutes each way.
A country divided
Brazil is the largest country in South America
in land mass and the fifth largest on Earth
with a populationof 190million. Brazil has the
seventh largest GDP and is, bymost accounts,
the fastest growing economy. Rich in natural
and human resources, this massive country
is divided by a complicated system of rivers
with the Amazon at its heart, separating its
territory into five distinctive regions.Travel in
Brazil by anything other than air is difficult, if
not nearly impossible, because of its massive
river system which divides the country like
great walls of water. The Rio Negro bridge
will connect the only urban center in the
region, Manaus, across the Rio Negro to the
city of Iranduba, which serves as the gate-
way to the interior of the Amazon, one of
the most remote and untouched regions of
the world. Making that connection is costly.
Originally projected at USD359-million, the
government decided to maximise competi-
tion for construction by breaking down the
bids into stages of construction. Every stage
of the project was separately contracted by
the government includingprimary surveying,
pillar construction and insertion, spanning of
the pillars with roadway, marine engineering,
lighting, and nautical signaling. The benefit
of this plan, of course, is that government
fundswouldbe spreadmore broadly through
smaller companies, none of which could take
on the entire project alone. The downside,
however, is that exact costs could not be
predicted over the multi-year project, and
particularly in a region where little massive
construction had been attempted before.
Taming a river
The Amazon region is well known for its
extremes in weather. In Manaus, the tropi-
cal monsoon climate means torrential rains
which create huge floods that annually in-
undate the surrounding areas: factors which
hinder mobility, especially considering that
the primary means of transportation across
the river is by ferry. The Rio Negro bridge
crew has to overcome these challenges as
they attempted to span a portion of the river
that experts knew very little about. In fact, so
littlewas known about the spanof riverwhere
the bridge was planned to cross that initial
projections required significant surveying
of the riverbed as well as monitoring of the
river currents. The task proved formidable.
Awork platformof 400 bargeswas neededon
the river as well as a crane that could hold up
to 300 tons to position the piles. But the eco-
nomic impact was also significant.The bridge
construction employedover 3 300workers di-
rectlywith an additional benefit of more than
8 000 workers tangentially involved with the
project. As Henrique Domingues, manager
of Obras Consorcia Rio Negro, describes it,
“We had big challenges. First, the Rio Negro
is a big, fast-flowing river, so we chose the
narrowest point where we could reasonably
cross. Second, little was known about the
geology of the region sowe had todo surveys
for the foundations.The foundations required
large-scale metal skirts that we had to drive
Amazon catherdral
Bridge facts
Length:
3 595 m
Road spans:
73 Cable-stayed section: 400 m
Center span height:
55 m
Central Mast Height:
10 m
3
Excavated piles:
246 Concrete used:
138 000 m
2
Steel used:
14 500 tons
Continued on page 48
