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MC Magazine |
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Portland’s King-Size Railing
The Martin Luther King Jr. viaduct in Portland,
Ore. Will feature precast concrete railing tough enough to
withstand 60 mph-plus vehicle impacts – and it will
look good too.
By Greg Snapper
Since 1937, the Martin Luther King Jr. viaduct
in Portland, Ore., has served as a major traffic artery. A
confluence of trade, Portland relies heavily on commercial
traffic flowing through the inbound and outbound lanes. But
due to years of wear and tear, the viaduct faces a structural
overhaul, and in the process, it will become safer and more
aesthetically appealing than its predecessor.
Precast architectural bridge railing will
line the east and west perimeters, serving not only as an
aesthetic spindle-railing touch, but as protection for drivers
as well. With a bid letting planned for early 2006, this new
design is on the table for Oregon Department of Transportation
and Portland officials to mull over, and the Portland community
has its finger on this project’s pulse.
Community members leading a design advisory
committee had a powerful voice in the viaduct’s architectural
elements, and they want to ensure that it will surpass both
the beauty and staying power of the current structure. The
envisioned precast railing will help accomplish both of these
goals.
Designed to deflect,
not grab
Making a bridge practical and pretty is a challenge ODOT officials
have dealt with since the newly designed viaduct’s inception,
says Stacy Codington, senior community affairs coordinator
for ODOT. “It’s a huge challenge – we are
walking a fine line between visual appeal and functionality,
with many interests invested in the process,” she says.
One of those interests happens to be the railing design, which
features four rails spanning the length of the 1,639-foot
viaduct. Two of these railings will line the perimeter –
the east and west edges of the viaduct – while the other
two will gird a 10-foot-wide space with planters down the
center. Each railing segment includes two 5.5-inch galvanized
tubes that are tied into the street-facing side and jut out
the same distance as the concrete rails. “The purpose
of this design is to contain and redirect the errant vehicle
back to its lane,” says Tony Stratis, bridge design
unit manager for ODOT.
“There’s really no chance for
car bumpers to get hung up on the railing,” says Jim
Morrison, owner of Pacific Precast Inc., a potential supplier
for the project. “The purpose of the design is to deflect,
not grab.” Additionally, the railing design has been
given a 60 mph-plus highway impact rating, making the precast
railing a two-pronged product – pretty and practical.
Terry Shike, bridge design task lead with
David Evans & Associates, says the complex installation
and placement of the state-of-the-art railing will be a challenge.
“By precasting portions of the rail and casting other
portions of the rail (on site), we will be able to provide
a good finished product and meet the intricate geometry challenges
of the project,” he says.
“At each bent of the viaduct, an 8-foot-long
pilaster will be installed along with a shorter but similar
pilaster installed at midspan,” he says. “Between
midspan and each bent there will be a total of four or five
intermediate pilasters.” The three types of pilasters
will carry the vehicle impact load into the deck. The bent
pilaster and midspan pilaster will be a combination of precast
and cast-in-place concrete, while the intermediate pilasters
will all be cast in place.
The top rail, spindles and curb will be
precast in units of four or five spindles. The precast units
will then be set in place into blockouts in the previously
cast-in-place deck. Once the precast units are placed, the
intermediate pilasters and the outside portions for the bent
and midspan pilasters will be cast-in-place.
On the west side of the viaduct, the rail
will be connected to a raised sidewalk, and on the east side,
the rail will be connected to the deck. The effectiveness
of installing the rail is vital to the safety of the traveling
public.
When the design team considered precast
railing for the Martin Luther King Jr. viaduct, it needed
something tangible before going any further with a precast
design. It needed evidence that the product would meet the
strict design demands of the architect, Lloyd Lindley, and
the highly involved community surrounding the viaduct. Morrison
leaped at the chance to offer his company’s services
and promptly cast a model of the railing spindles for ODOT.
“The sample looked great,” says
Shike. “We think we will get a better product in the
end.”
The original Martin Luther King Jr. Boulevard
portion of the structure was built by Hoffman Construction
Co. of Portland in 1937 at a cost of $459,000. This Roosevelt-era
Works Progress Administration project brought many needed
jobs to Portland-area residents. Now the current proposal
and construction of the new viaduct could face a high price
tag. With federal and state funding, total costs could hit
$40 million to $50 million.
After years of design consultation from
ODOT and the surrounding Portland community, Dave Thompson,
communications coordinator for ODOT, says the robust public
involvement coupled with the determination of the viaduct
design team will give the city of Portland a bridge it can
be truly proud of. “The viaduct will be a welcome replacement
upon its opening,” says Thompson. “It will renew
the economic lifeblood of Portland once traffic picks up again.”
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MC Magazine July/August 2005 Table of Contents
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