The growing popularity of timber bridges is not only due to
their economy, strength, durability and nostalgic ties to America's early
history. It also is their warm, aesthetic presence and harmony with the
environment that causes design firms and local government agencies to value
this historical material much as their ancestors did.
Many of the bridges which received awards in the recent
National Timber Bridge Award competition were specifically designed to enhance
and protect the delicate environments where they span creeks, rivers, waterways
National Timber Bridge Awards were presented to 15
outstanding bridges located across the nation. The major sponsors of the program
are APA-The Engineered Wood Association, the American Institute of Timber
Construction, the U.S. Forest Service-Wood in Transportation Program and the
Federal Highway Administration. Supporting sponsors are the American Wood
Preservers Institute and ROADS & BRIDGES magazine.
Judges for the competition were Thomas Williamson, P.E.,
APA-The Engineered Wood Association; Michael Caldwell, P.E., American Institute
of Timber Construction; Ed Cesa, U.S. Forest Service; and Sheila Duwadi, P.E.,
Federal Highway Administration.
The following is a brief description of some of the
first-place award winners.
Vehicular Bridge (main span greater than 40 ft)
Military Road Bridge
When two counties in upper New York decided to replace a
deteriorating concrete bridge over West Canada Creek, they turned to an
engineering firm that recommended a glued laminated spandrel arch design with
glulam bents, deck and railings.
The underdeck design was chosen for the Military Road Bridge
based on the advantages of geometric constraints, protection from weather,
vehicular impact, ease of construction and competitive costs.
"Additionally, glued laminated timber was selected for
its architecturally appealing features," the engineers reported.
The bridge deck has longitudinal glulam timber panels on
transverse glulam floor beams.
Special galvanized saddle connections tied the bents to the
glulam arch segments. The arches span 132 ft. The total length of the bridge is
180 ft and the width is 27.5 ft. Total construction cost was $1,001,000.
Owner: Herkimer and Oneida Counties, N.Y.
Design/Consulting firm: Barton & Loguidice, P.C.,
Contractor/Erector: Tioga Construction Co., Herkimer, N.Y.
Engineer: Barton & Loguidice, P.C., Syracuse, N.Y.
Another vehicular bridge over 40 ft which won an Award of
Merit in the competition was the Gardiner Road Bridge in Port Townsend, Wash.
Vehicular Bridge (main span less than 40 ft)
The designers of this 75-ft-long timber bridge had to operate
within stringent restrictions which required that any crossing of the delicate
wetlands in Washington, Conn., must make only a minimum impact on the
environment. It is 11 ft wide.
Three pairs of graceful 103?4-in.-deep curved glulam
timber sections create the bridge structure. Each glulam section spans 25 ft
between concrete piers and abutments.
Glulam sections were formed as arches and then laid on their
sides. Each panel acted as a monolithic slab, transferring and spreading the
wheel loads of vehicles laterally. Glulam rails form wheel curbs that trace the
deck's curved edge.
Owner: II Poggio, Washington, Conn.
Design/Consulting Firm: Gray Organschi Architecture, New
Engineer: Gibble Norden Champion Brown, Old Saybrook, Conn.
This graceful asymmetrical cable-stayed bridge across the
Saco River connects homes in Harts Location, N.H., to the outside world and
carries skiers and hikers to Mount Washington. Designers were challenged by the
special requirements set down for the new bridge which directed that the span
be unobtrusive with environmental appeal, require low maintenance, not impede
the spring runoff and be built within a limited budget.
Basic materials include glued laminated timber girders and
deck, galvanized steel pipe rail, a 53-ft steel tower and galvanized cable. The
unique structure is the only asymmetrical cable-stayed bridge in New England.
Because of the creative design, there are no piers in the Saco River to impede
spring runoff or impact this classic New Hampshire trout stream.
The bridge is 165 ft long. It is handicap accessible with a
5-ft width which provides enough space for a wheelchair to turn around.
Owner: Town of Hart's Location, N.H.
Design/Consulting Firm: H.E. Bergeron Engineers, Conway,
Contractor/Erector: Bayview Construction, Portsmouth, N.H.
Engineer: H.E. Bergeron Engineers, Conway, N.H.
Rehabilitation of Existing Bridges
The waters of history flow swiftly over and under the
Tohickon Aqueduct "water bridge" in Bucks County, Pa. The glued
laminated timber bridge carries the Delaware Canal on three spans totaling 210
ft over Tohickon Creek.
The first aqueduct bridge in this location was built during
the 1830s, when Andrew Jackson was president. The current timber aqueduct is
the fifth bridge, following the deterioration of previous metal truss and
concrete designed spans built in the past century.
The current bridge is a timber burr truss design. It is
engineered to bear the water loads over the three 66-ft spans of the Tohickon
Aqueduct, supporting 350 tons of water within its trunkway. In the
rehabilitation, the superstructure system allowed the timber trusses to bear
directly on new caps on the existing stone substructures. The trusses were
engineered to be redundant so either the trusses or the arches alone could bear
the fully loaded structure. The new timber tow path was cantilevered over the
creek and the entire structure was sheathed as a "covered bridge."
The cost was $2.1 million. An estimated $1 million was saved
based on revised specifications for modern glulam timber fabrication and
Owner: Pa. Dept. of Conservation and Natural Resources,
Design/Consulting Firm: Simone Jaffe Collins Inc. Landscape Architecture,
Contractor/Erector: J.D. Eckman Inc., Atglen, Pa.
Structural Engineer: DCF Engineering Inc., Cary, N.C.
Project Engineer: Pa. Dept. of Conservation and Natural
Resources, Harrisburg, Pa.
Substructure Engineer: Pa. Dept. of Environmental
Protection, Harrisburg, Pa.
Embarras River Bridge
Covered bridges may be the only American structures which
are still built with the same designs and craftsmanship employed during the
The first-place award winner for covered bridges in this
year's award program is the Embarras River bridge in Cumberland County, Ill. It
is reported to be the longest single span covered timber bridge in the U.S.
without a posted load restriction. The new bridge is reminiscent of the original
span over the Embarras River, built in the early 1800s as part of the historic
The $2.8 million bridge is a 200-ft single-span structure
which utilizes a combination of parallel chord trusses and three-hinged
parabolic arches to satisfy stringent loading and deflection criteria. It was
designed to be a cultural and tourist attraction as well as a functioning
highway bridge on U.S. Highway 40.
Owner: Cumberland County Highway Dept., Toledo, Ill.
Design/Consulting Firm: Rhutasel and Associates, Centralia,
Contractor/Erector: O'Neil Bros. Construction, Danville,
Engineers: Elmer G. Pyle, P.E., S.E., Rhutasel and
Associates Inc. and Enterprise Engineering Consultants, Peshtigo, Wis.
For more information about the timber bridge award program,
contact Tom Williamson, APA-The Engineered Wood Association, 7011 S. 19th St.,
Tacoma, WA 98466, at 253/620-7407, e-mail: [email protected].