Walsh Construction Co. and PCL Civil Constructors, in a joint venture partnership, currently are building the Q-B Pearl Harbor Memorial Bridge. The Connecticut Department of Transportation awarded the $417 million project last year. The program is a federally-funded mega program called the I-95 New Haven Harbor Crossing Corridor Improvement Program. The Pearl Harbor Memorial Bridge broke ground in December 2009 with an expected completion date of mid-2015.
The Pearl Harbor Memorial Bridge is a 7.5-mile stretch of highway that spans the Quinnipiac River. The current bridge was designed and constructed in the late 1950s to carry 40,000 vehicles daily. Today, the bridge averages more than 140,000 vehicles per day. In order to accommodate the higher daily traffic load, a 10-lane, twin extradosed, cast-in-place segmental box girder structure will replace the existing six-lane, steel-plate girder bridge. The term “extradose” refers to an outer or exterior surface, and indicates the use of stays that act as exterior post-tensioning tendons on the box girder. Unlike cable-stay bridges, extradosed bridges do not carry the entire deck load through the stays, but rather through both the stays and the deck.
Extradosed bridges are hybrid structures that use shorter towers to support deck segments with cables, and, therefore, are well-suited to areas where a lower profile and long span are required for their construction. “The benefit of this bridge’s design is the short towers,” says senior project manager Mike Bardin. “The towers provide less interference with the local airport, and it meets the FAA restrictions on air space.”
Additionally, the bridge must provide a main span of 515 feet to accommodate the navigational channel. The finished structure will be 1,013 feet long, and will have six tower legs – each 144 feet tall – that project 75 feet above the deck, and support three planes of eight stay cables.
An extradosed bridge lends itself to longer spans than a conventional girder bridge. This was a benefit for the design of the Pearl Harbor Memorial Bridge in that the new bridge will have a longer main span than the existing bridge. “They’ve built extradosed bridges in other parts of the world, but this bridge is a first of its kind in the United States,” says Bardin.
The project includes building more than 3,500 linear feet of approach structure in addition to the main span, as well as demolishing the existing bridge. “We’ll complete the northbound lanes first. Then we will switch the traffic to the new bridge, begin demolition on the existing bridge before doing the southbound lanes,” explains Bardin.
The bridge will consist of 65 land-based drill shafts and 20 shafts that are over the water.
“There are two separate drilling operations for this project,” says Blake Yaffee, foundation engineer. “For the land-base drilling, we’re using a Bauer BG 40 rig to drive casing for the bridge’s foundation. This particular rig allows us to twist down 3.35-meter-diameter casings. Using this method was twice as fast as using a vibratory method, and allowed us to cut down on production hours.”
Crews are able to drill the 11-foot-diameter casing into the ground at a depth of 50 feet in about 2 days to 3 days. “Once we drill the casing, we clean out the foundation using airlift methods prior to pouring the concrete,” explains Yaffee. “It takes 19 concrete truck loads to fill the 11-foot casing for this bridge’s foundation.”
Walsh Construction Co. is a Chicago-based general contracting, construction management and design-build firm. The firm has experience with a wide variety of building, civil and transportation sectors. Maintaining regional offices across the United States, Walsh Construction operates using Union Labor and Union Subcontractors. PCL Civil Constructors Inc. is part of the PCL family of companies, the seventh largest contracting organization in the United States, and the largest contracting organization in Canada. The PCL family has offices in 27 major centers across Canada, continental North America, the Hawaiian Islands and the Caribbean.