New bridges will be
new Twin Span Bridge will be taller, stronger and more
hurricane-resistant than its predecessor. Wind and
wave action from Hurricane Katrina battered the existing
bridge and knocked more than 400 concrete deck spans out of
alignment. Fifty-eight other concrete spans were
toppled into Lake Pontchartrain. To illustrate the
ferocity of the storm, each of the concrete deck spans
weighed in excess of 300 tons.
designing the new bridge the Louisiana DOTD established
rigorous standards for combating hurricane wind and wave
action. The new standards result in bridges that are
better able to resist lateral forces and in some ways
resemble those built in earthquake zones.
new bridge is 21 feet higher than the old one (30 feet
versus 9 feet), but that’s only part of the difference,”
said John Horn of Volkert Construction Services.
“Included in the design are shear keys and reinforced steel
and concrete tie-ins between the bridge decks and caps that
will help prevent misalignment and toppling due to storm
surge. In addition, the entire bridge is being
constructed using high-performance concrete.”
innovations are adding some time and cost to the project,
but Horn says they will result in a more robust bridge.
estimated lifespan of the existing bridge was 40 years, the
new bridge will have a lifespan of 100 years. That
represents a good investment of taxpayer dollars.”