Waldo-Hancock BridgeEdit profile
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. The bridge was retired in 2006 as the new Penobscot Narrows Bridge was opened just a few yards away.
The bridge is 2,040 feet (622 m) long with a clear center span 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) sidewalks. It uses stiffening trusses that are 9 feet (2.7 m) deep. Each of the main suspender cables is 9-5/8 inches (24 cm) in diameter, and consists of 37 strands of 37 wires. The deck 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, of Robinson and Steinman, was the designer. The bridge was fabricated by American Bridge Company (superstructure) and Merritt-Chapman & Scott (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 in Portland, Oregon, 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 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 and Golden Gate Bridge.
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, 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.