THE
STILLWATER ROAD (SHEA) BRIDGE
Cumberland,
Rhode Island
The Stillwater Road Bridge or Shea Bridge, as it is also known, was
built in July, 1886 by the Berlin Iron Bridge Company of East Berlin,
Connecticut. It features a parabolic, lenticular truss system, a design
patented and used exclusively by that company. Of the several thousand
bridges with this design that were constructed nationwide between 1870
and 1900, fewer than 5 percent remain standing today.
In Rhode Island, the Stillwater Road Bridge is one of only two remaining
lenticular truss bridges, and the only one built as a highway truss.
For more than a century the bridge was an integral part of the textile
mill village of Georgiaville, in the town of Smithfield, Rhode Island
(see figure 1 above). The bridge was determined to be individually eligible
for listing in the National Register of Historic Places in 1984. A year
later, the Georgiaville Historic District was listed. Finally, in November
1989, Stillwater Bridge was documented according to Historic American
Engineering Records (HAER) standards after it had been marked for demolition
and replacement.
Problem
The almost predictable physical threats to historic bridges --deferred
maintenance, harmful deicing salts, and overloading--have accelerated their
rate of deterioration in recent years. In addition, many do not meet current
loading and safety requirements. The Surface Transportation and Uniform
Relocation Assistance Act of 1987 calls for the preservation, rehabilitation,
and re-use of historic bridges and makes such projects eligible for federal
funding. The Intermodel Surface Transportation Efficiency Act of 1991 acknowledges
the urgent need to upgrade our nation's aging highway infrastructure. Together,
the laws create a momentum for positive action.
Preservation projects for historic bridges have the highest success
rate--within existing law--when partnerships are forged among transportation
planners, preservationists, engineers, state and local governments and
the interested public. Creative planning, innovative design solutions,
modem technologies, and possible financial savings over new construction,
offer the best hope to ensure that historic bridges remain in active
use. In the case of the aging Stillwater Road Bridge, the town of Smithfield
began searching for ways to replace it in the1960s. The relatively light
construction of the span, coupled with the deteriorated condition of
its structural members, were the primary reasons for its slated removal.
In 1984 the town recommended that the Rhode Island Department of Transportation
(RIDOT) assume management of the bridge project. Although retaining the
bridge on its original site was possible, RIDOT concluded this was not
a viable option; an engineering analysis determined that bringing the
structure up to current load requirements would have required replacement
of most of the supporting truss members.
After a century of use, the bridge showed signs of major deterioration.
Three of the four upright posts were bent from automobile collisions.
The U-bolt floorbeam hangers had rusted, the result of moisture and dirt
collecting on the flange. The lattice girder stiffeners (zero-force members
which serve to prevent "racking" or lateral movement) had lost
their latticework and were severely corroded, In addition, the endposts
of the bridge showed signs of serious decay (see figures 2 and 3).
| While moving a historic resource into a new context is generally
not a recommended preservation solution, in the case of historic
bridges, moving is frequently the only way to assure their physical
protection as well as continued use. In addition, making certain
structural alterations so that a historic bridge can fit the new
site is parallel to altering a building for a new use--if done with
sensitivity so that the historic character is not jeopardized in
the process, the work meets the Secretary of the Interior’s
Standards for Rehabilitation. |
|
