Deer Isle Bridge
Encyclopedia
The Deer Isle Bridge is a suspension bridge
spanning Eggemoggin Reach in the state of Maine
. The bridge is the only vehicular connection from the Maine mainland to Little Deer Isle, one of the segments that make up the island. The span was completed in March 1939 with a main span of 329 meters (1,088 ft). The bridge was designed by Holton Duncan Robinson and David Bernard Steinman. It encountered wind stability problems that were similar to those of the Whitestone Bridge and the original Tacoma Narrows Bridge
, which collapsed shortly after it opened. The problems led to modifications which included numerous cable stays connecting cables to the tower and tower to the deck. The span today carries two narrow lanes of State Route 15.
A re-decking project was completed in May 2008. Repainting started in mid-2010 has been completed.
The challenges facing David B. Steinman, his firm, and their contractors were numerous. The popularity of Eggemoggin Reach as a yachting area called for a 200 feet (61 m) wide channel at midspan with a minimum 85 feet (25.9 m) underclearance, placing the roadway at 98.7 feet (30.1 m) above mean water level. At the same time, the depth required for foundations at this location called for minimizing the length of the approach spans. This height problem was solved by employing steep 6.5% approach grades and a fairly short 400 feet (121.9 m) vertical curve at the center of the main span. In this manner, the needed height was attained and the approach viaducts were kept to a minimum length.
The project was also complicated by its required early-summer completion date, meaning that much of the work had to be done during the winter and early spring months when weather conditions posed a significant challenge. Robinson and Steinman and their contractors solved this difficulty by prefabricating many of the components offsite and completing the bulk of the assembly quickly, working between high tides. Site-specific innovations in prefabrication and construction methods minimized outdoor work at the site and departed from conventional bridge-building practice. This careful consideration and planning resulted in a project completed on schedule and at low cost, despite the extreme conditions.
The substructure, in particular, employed prefabrication at an unprecedented level. Instead of assembling the steel sheet-pile cofferdams and the metal forms for the main tower pedestals on site, Merritt-Chapman & Scott
had them prefabricated at their yard on Staten Island and brought to Maine by barge. Their use of secondhand steel materials for the dams, along with the prefabrication and careful timing of the construction schedule, saved a great deal of money. The prefabricated dams were assembled for use on barges near the work site. After mud was removed from the bottom and the rock foundation carefully sounded, the dam bases were torch-cut to fit the profile of the irregular bedrock on which they were to be set. Finally, the dams were filled with concrete.
On the superstructure, pre-stressed twisted-strand cables invented by the designer were used to advantage on both the main strands and the suspenders, meaning the time-consuming and expensive field adjustments were unnecessary. These cables debuted in the U.S. in 1931 on Steinman and Robinson’s Waldo-Hancock Bridge
near Bucksport, Maine, and their St. Johns Bridge
in Portland, Oregon. A new connection method, which used sleeve nuts to connect each main strand socket to its anchorage rod, was also used. These connections, invented by Robinson and first used on the Thousand Islands Bridge the previous year, made small adjustments to the main strands very easy.
Before the bridge was finished, unexpected wind-induced motion in the relatively lightweight deck indicated the need for greater stability. Diagonal stays running from the main cables to the stiffening girders on both towers were added to stabilize the bridge. However, the bridge’s motion during unusually severe storms in the winter of 1942–1943 caused extensive damage and destroyed some of the stays. With the recent collapse of the Tacoma Narrows Bridge in everyone’s mind, stronger and more extensive longitudinal and transverse diagonal stays were added.
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...
spanning Eggemoggin Reach in the state of Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
. The bridge is the only vehicular connection from the Maine mainland to Little Deer Isle, one of the segments that make up the island. The span was completed in March 1939 with a main span of 329 meters (1,088 ft). The bridge was designed by Holton Duncan Robinson and David Bernard Steinman. It encountered wind stability problems that were similar to those of the Whitestone Bridge and the original Tacoma Narrows Bridge
Tacoma Narrows Bridge (1940)
The 1940 Tacoma Narrows Bridge was the first incarnation of the Tacoma Narrows Bridge, a suspension bridge in the U.S. state of Washington that spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed...
, which collapsed shortly after it opened. The problems led to modifications which included numerous cable stays connecting cables to the tower and tower to the deck. The span today carries two narrow lanes of State Route 15.
A re-decking project was completed in May 2008. Repainting started in mid-2010 has been completed.
History
The Deer Isle-Sedgwick Bridge, named for the two townships it connects, was the first bridge built between Deer Isle and the mainland, replacing an inadequate ferry crossing system and effectively opening the island to tourism opportunities. It is notable for the innovation of its designers and contractors in creating a durable, long-span, high-level structure across a navigable arm of the Atlantic at minimal cost. Unprecedented use of prefabricated and previously used materials simplified construction and minimized costs, and much of the outdoor work was completed under poor weather conditions.The challenges facing David B. Steinman, his firm, and their contractors were numerous. The popularity of Eggemoggin Reach as a yachting area called for a 200 feet (61 m) wide channel at midspan with a minimum 85 feet (25.9 m) underclearance, placing the roadway at 98.7 feet (30.1 m) above mean water level. At the same time, the depth required for foundations at this location called for minimizing the length of the approach spans. This height problem was solved by employing steep 6.5% approach grades and a fairly short 400 feet (121.9 m) vertical curve at the center of the main span. In this manner, the needed height was attained and the approach viaducts were kept to a minimum length.
The project was also complicated by its required early-summer completion date, meaning that much of the work had to be done during the winter and early spring months when weather conditions posed a significant challenge. Robinson and Steinman and their contractors solved this difficulty by prefabricating many of the components offsite and completing the bulk of the assembly quickly, working between high tides. Site-specific innovations in prefabrication and construction methods minimized outdoor work at the site and departed from conventional bridge-building practice. This careful consideration and planning resulted in a project completed on schedule and at low cost, despite the extreme conditions.
The substructure, in particular, employed prefabrication at an unprecedented level. Instead of assembling the steel sheet-pile cofferdams and the metal forms for the main tower pedestals on site, Merritt-Chapman & Scott
Merritt-Chapman & Scott
Merritt-Chapman & Scott, nicknamed "The Black Horse of the Sea", was a noted marine salvage and construction firm of the United States, with worldwide operations. The chief predecessor company was founded in the 1860s by Israel Merritt, but a large number of other firms were merged in over the...
had them prefabricated at their yard on Staten Island and brought to Maine by barge. Their use of secondhand steel materials for the dams, along with the prefabrication and careful timing of the construction schedule, saved a great deal of money. The prefabricated dams were assembled for use on barges near the work site. After mud was removed from the bottom and the rock foundation carefully sounded, the dam bases were torch-cut to fit the profile of the irregular bedrock on which they were to be set. Finally, the dams were filled with concrete.
On the superstructure, pre-stressed twisted-strand cables invented by the designer were used to advantage on both the main strands and the suspenders, meaning the time-consuming and expensive field adjustments were unnecessary. These cables debuted in the U.S. in 1931 on Steinman and Robinson’s Waldo-Hancock Bridge
Waldo-Hancock Bridge
The Waldo–Hancock Bridge was the first long-span suspension bridge erected in Maine, as well as the first permanent bridge across the Penobscot River below Bangor. The name comes from connecting Waldo and Hancock counties...
near Bucksport, Maine, and their St. Johns Bridge
St. Johns Bridge
The St. Johns Bridge is a steel suspension bridge that spans the Willamette River in Portland, Oregon, USA, between the St. Johns neighborhood and the northwest industrial area around Linnton. It is the only suspension bridge in the Willamette Valley and one of three public highway suspension...
in Portland, Oregon. A new connection method, which used sleeve nuts to connect each main strand socket to its anchorage rod, was also used. These connections, invented by Robinson and first used on the Thousand Islands Bridge the previous year, made small adjustments to the main strands very easy.
Before the bridge was finished, unexpected wind-induced motion in the relatively lightweight deck indicated the need for greater stability. Diagonal stays running from the main cables to the stiffening girders on both towers were added to stabilize the bridge. However, the bridge’s motion during unusually severe storms in the winter of 1942–1943 caused extensive damage and destroyed some of the stays. With the recent collapse of the Tacoma Narrows Bridge in everyone’s mind, stronger and more extensive longitudinal and transverse diagonal stays were added.
External links
- data page at Library of CongressLibrary of CongressThe Library of Congress is the research library of the United States Congress, de facto national library of the United States, and the oldest federal cultural institution in the United States. Located in three buildings in Washington, D.C., it is the largest library in the world by shelf space and...
HAER site