Waldo-Hancock Bridge - AbsoluteAstronomy.com

The Waldo–Hancock Bridge was the first long-span suspension bridge

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...

erected in 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...

, as well as the first permanent bridge across the Penobscot River

Penobscot River

The Penobscot River is a river in the U.S. state of Maine. Including the river's West Branch and South Branch increases the Penobscot's length to , making it the second longest river system in Maine and the longest entirely in the state. Its drainage basin contains .It arises from four branches...

below Bangor

Bangor, Maine

Bangor is a city in and the county seat of Penobscot County, Maine, United States, and the major commercial and cultural center for eastern and northern Maine...

. The name comes from connecting Waldo

Waldo County, Maine

Waldo County is a county located in the U.S. state of Maine. As of 2010, the population was 38,786. Its county seat is Belfast.Waldo County was founded on 7 February 1827 from a portion of Hancock County...

and Hancock

Hancock County, Maine

Hancock County is a county located in the U.S. state of Maine. As of 2010, the population was 54,418. Its county seat is Ellsworth. It was incorporated on June 25, 1789...

counties. The bridge was retired in 2006 as the new Penobscot Narrows Bridge

Penobscot Narrows Bridge

The Penobscot Narrows Bridge is a cable-stayed bridge over the Penobscot River near Bucksport, Maine. It replaced the Waldo–Hancock Bridge, built in 1931. The new bridge is long. It is one of three bridges in the U.S...

was opened just a few yards away.

The bridge is 2,040 feet (622 m) long with a clear center span

Span (architecture)

Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...

of 800 feet (244 m) between towers. It has two 350 foot (107 m) side spans and carries a 20 foot (6 m) wide roadway with two 3-1/2 foot (1 m) sidewalk

Sidewalk

A sidewalk, or pavement, footpath, footway, and sometimes platform, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade and is normally separated from the vehicular section by a curb...

s. It uses stiffening truss

Truss

In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...

es that are 9 feet (2.7 m) deep. Each of the main suspender cable

Cable

A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...

s is 9-5/8 inches (24 cm) in diameter, and consists of 37 strands of 37 wires. The deck

Deck (bridge)

A bridge deck or road bed is the roadway, or the pedestrian walkway, surface of a bridge. It is not to be confused with any deck of a ship.The deck may be of concrete,wood which in turn may be covered with asphalt concrete or other pavement...

is 135 feet (41 m) above water level to allow passage of large ships. The total cost of the span was less than $850,000 in 1931 dollars (about $12 million in 2010 dollars), significantly under its allocated budget.

Construction

David B. Steinman

David Bernard Steinman was an American structural engineer. He was the designer of the Mackinac Bridge and many other notable bridges, and a published author. He grew up in New York City's lower Manhattan, and lived with the ambition of making his mark on the Brooklyn Bridge that he lived under...

, of Robinson and Steinman, was the designer. The bridge was fabricated by American Bridge Company

American Bridge Company

The American Bridge Company is a privately held civil engineering firm specializing in the construction and renovation of bridges and other large civil engineering projects, founded in 1900, and headquartered in Coraopolis, Pennsylvania, a suburb of Pittsburgh.-Products and industry positioning:The...

(superstructure) and 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...

(substructure).

Technologically, the Waldo–Hancock Bridge represents a number of firsts. It was one of the first two bridges in the U.S. (along with the 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

Portland, Oregon

Portland is a city located in the Pacific Northwest, near the confluence of the Willamette and Columbia rivers in the U.S. state of Oregon. As of the 2010 Census, it had a population of 583,776, making it the 29th most populous city in the United States...

, completed in June, 1931) to employ Robinson and Steinman’s prestressed twisted wire strand cables, which were first used on the 1929 Grand Mère Suspension Bridge over the Saint-Maurice River

Saint-Maurice River

The Saint-Maurice River is a river in central Quebec which flows south from Gouin Reservoir to empty into the Saint Lawrence River at Trois-Rivières, Quebec. The river is 563 km in length and has a drainage basin of 43,300 km² ....

in Quebec. The prefabrication and prestressing of the cables decreased the number of field adjustments required, saving considerable time, effort, and money. As an additional experiment in efficiency, the Waldo-Hancock cables were marked prior to construction, ensuring proper setting. This method had never been used before and proved successful in this instance. These innovations, invented and pioneered by Steinman, were a significant step forward for builders of suspension bridges.
The Waldo-Hancock was also the first bridge to make use of the Vierendeel truss in its two towers, giving it an effect that Steinman called “artistic, emphasizing horizontal and vertical lines.” This attractive and effective truss design was later used in a number of important bridges, including the Triborough Bridge

Triborough Bridge

The Robert F. Kennedy ' Bridge, formerly known as the Triborough Bridge , is a complex of three separate bridges in New York City, United States...

and Golden Gate Bridge

Golden Gate Bridge

The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...

.

The Waldo–Hancock Bridge was noted at the time for its economy of design and construction. It cost far less than had been appropriated by the State Highway Commission, which enabled the construction of a second bridge between Verona Island and Bucksport.

Rehabilitation and replacement

The bridge was opened as a toll bridge to retire the bonds issued to finance construction. Tolls were lifted on 31 October 1953.

Work was undertaken to rehabilitate the bridge starting in 2000 by Cianbro and Piasecki Steel Construction Corp. with cable work by Williamsport Wirerope Works Inc, by focusing on strengthening the cables. The two cables were done separately, one a time. Piasecki Steel Construction Corp., Castleton, N.Y., rehabilitated the north cable in 2002. At this point the bridge was discovered to be irreparable. Work then shifted to temporary strengthening. For the south cable, MDOT in August 2003 hired Pittsfield, Maine-based Cianbro Corp. under a $4-million emergency contract.

The rehabilitation used a single wire thickness (2-inch (5.1 cm) diameter galvanized helical 91-wire strands.) to facilitate fabricating and installing the cables more quickly. New concrete anchorages with up to 30-foot (9.1 m) long anchor rods were built by Cianbro. Crews installed continuous runs of strands on new saddles bolted and welded on new base plates atop cable bents and the main towers. Workers placed two groups of four strands 12 feet (3.6 m) above each main cable to allow for pulls. Each strand weighs 4 tons (3.6 metric tons). A rope pull was walked across, connected to a 7/8-inch (2.2 cm) pull cable, then winched back across and connected to the strand, which was fed through a tensioner holding back about 15,000 pounds (6,803 kg) to smooth the pull.

“We hooked and rehooked one strand per day on average,” says Archie J. Wheaton, Cianbro project superintendent. “The strands were connected to anchor rods; then we set the sag.” The new auxiliary cables are connected to existing double suspender cables by 1 1/8 inch (2.9 cm) steel rods, then tensioned with 30-ton (27.2 metric ton) jacks, bringing the new cables about 3 feet (0.9 m) from the main cables.

A new construction, the Penobscot Narrows Bridge

Penobscot Narrows Bridge

, was built alongside the older one. The new bridge was opened to traffic on December 30, 2006, at which point the Waldo–Hancock Bridge was ceremoniously closed. Barricades have been erected at both ends closing the bridge to both cars and pedestrians.

External links

— major source of information used in article, although not directly cited.

Entry at Bridgemeister.com (includes builders plate)
Entry at Bridgemeister.com (includes distance shots)
entry on reconstruction at BridgePros.com
Recabling project from McGraw Hill Engineering News Record site (effort ended up being a temporary stopgap)
Replacement project at Maine DOT site

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Construction

Rehabilitation and replacement

Further reading

External links