Jul 23, 2002

Checking crystal bridges

Steuben County treats spans with labor-saving engineering and design tools

New York’s Steuben County is famous for just what you
might guess: Steuben crystal. The maker of fine crystal animals, bowls and
candlesticks took its name from the county, and its parent company, Corning
Inc., took its name from one of Steuben County’s largest cities, where it
is headquartered. Corning’s factory still makes the Pyrex cookware that
made it famous 80 years ago, but since then the old glass works has become a
global giant, churning out high-tech products like fiber-optic cable and the
silica windows for NASA spacecraft.

At 1,600 sq miles, Steuben County is one of the largest
counties in New York, slightly smaller than the state of Delaware. But it is
largely a rural place, latticed throughout with rivers and streams with
vineyards rolling among the Finger Lakes in the north and Amish villages
nestled in the south. With few town-maintained bridges, the burden of taking
care of the county’s infrastructure often falls upon the county
department of public works (DPW).

The county has 678 miles of road to look after, and chances
are that each of those roads depends on a series of large and small bridges to
get across the streams that criss-cross the county. In all, the county
maintains more than 700 of these bridges, about half of them smaller than 20 ft

“We’ve got a lot of water up here,” said
Kent Longacre, a CAD specialist with the DPW.

To track and design bridge projects, along with other tasks
such as realigning roads and rebuilding intersections, the DPW relies on
Autodesk Land Desktop (Circle 921) and its companion products, Survey and Civil
Design (Circle 922). With labor-saving engineering and design tools that are
easy to learn, the department’s small staff is able to handle projects
that it might otherwise hire out to contractors.

[if !supportEmptyParas] [endif]

Troubled water

Each year in the fall and winter, when the leaves are off
the trees and won’t obscure the surveyors’ sightlines, the DPW
inspects its bridges and selects a number of them to survey and improve. Using
a Leica surveying gun that allows them to enter labels for features as they
work, county surveyors measure the GPS coordinates of the banks of a river
leading up to a bridge, including trees, buildings or other landmarks. They
download their raw data into Autodesk Survey, which creates a field book and
captures the labels.

From this data, DPW engineers can create a map of the stream
with terrain features in a “real-world” coordinate system, adding
in local watershed details if necessary.

“Land Desktop allows us to look at vertical profiles
and sections of the river, which we can check against previous maps to see if
the banks are eroding and need reinforcement,” said Longacre.

A bridge structure may need repairs if it has deteriorated
or is skewed improperly along the stream, channeling water the wrong way. In a
downpour, fast-moving water could overwhelm such a bridge, degrading its banks
or even undermining the road surface above. If the bridge needs to be realigned
or repaired, DPW engineers plan the improvements using Autodesk Civil Design,
sometimes designing new concrete beams, sending the drawings out to a beam

“We’re one of the few counties in New York that
does our own bridge design and construction in-house,” Longacre

In addition to bridges, the Steuben DPW regularly selects
parts of its road system for safety improvements—flattening out stretches
of hilly or bumpy road, extending sight lines, realigning dangerous curves. On
a road where the surface has deteriorated over the years, causing the pavement
to dip up and down, surveyors will take vertical measurements at intervals and
then view the road’s topography. Using Land Desktop, engineers can create
a digital terrain model of the road, looking at several profile cross
sections—slices of the road they can compare with previous years. Land
Desktop shows them precisely where the road has deteriorated and calculates how
much fill the DPW will need to make it level and safe again.

The same volume-measuring features in Land Desktop allow
Longacre to monitor how high the surface levels are rising from month to month
in the county’s two landfills.

[if !supportEmptyParas] [endif]

Dangerous curves

Realignment work on road curves has several elements.
Sometimes a curve will need to be “superelevated” so that its outer
edge is higher, the same way auto racetracks have steeper banks around their
curves. Banking the road this way allows a driver to move around a corner at
highway speed without veering off into a ditch. Sometimes the angle of the
curve is too tight or it is elevated on the wrong side due to the pressures of
years of traffic; these flaws show up when engineers survey the road and view
its topography in Land Desktop. Civil Design makes it simpler to design a
realignment that brings the road up to various standards for geometry and sight
distance mandated by the New York State DOT.

“Civil Design has variables for things like banking,
speed tables and superelevations,” said Longacre. “It will
automatically calculate the transitions in and out of the curve, the necessary
angles and elevations, because the DOT codes and standards are already built
in. That makes it a lot easier to do those calculations when you’re
mapping out the realignment.”

The DPW also appreciates the ability to do what Longacre
calls “what-ifs.” Autodesk Civil Design “allows us to do
three or four different scenarios for changing a curve, which is a real
benefit,” he said. “To help us make the right decision, we’ll
do several models of the same road realignment. We just put different numbers
into a table and [Civil Design] has an extension that will immediately adjust
the drawing in front of you.”

After plotting and printing the different options, they show
them to the agency’s chief engineer.

“We point to the particular positives of each, and he
can choose the best one,” Longacre said.

[if !supportEmptyParas] [endif]


Having a central repository for drawings in the DPW allows
different engineers and drafters to collaborate, building on other
people’s work.

“We’re all networked, so one of us can call up
the site plan from the database, rename it as a new file and use it for
something he has to do,” Longacre said. “My colleagues here
don’t have to design things from scratch on paper anymore; they can just
work off my drawings, and vice versa.”

Another benefit of in-house design is that the
agency’s maps are more accessible.

“For example, the other day the head of our road
construction crews wanted to see a cross section, so he just walked over to the
designer and she pulled it,” Longacre said. “If we had given the
job to a consultant, we’d probably have to mark up a drawing and send it
out, and it would take much longer.”

“The bottom line is, if we can do highway designs
ourselves, we save the taxpayers money,” Longacre said. “And
we’re doing a pretty good job of handling it ourselves.”

About the author