Prefabricated steel bridges provide an efficient and cost-effective bypass option when a bridge must be replaced and closing the road or railroad for an extended period would create unacceptably long detours and transportation disruption. In other applications, the built-to-spec structures can serve as quickly installed, permanent replacements for failing bridges facing emergency closure.
Acrow Bridge recently completed installation of a temporary detour bridge over the Umauma Stream on the Island of Hawaii. The 390-foot-long, three-span steel bridge is being used as a bypass on Mamalahoa Highway during repairs to a historically significant steel girder and trestle bridge. Acrows bridge is expected to be in operation until summer 2016.
Installation of the structure by Acrow engineers and field staff along with contractor Hawaiian Dredging Construction Company presented special challenges. The tower heights of 85 and 90 feet, along with the seismic design requirements, necessitated working with KSF Engineering in Honolulu on special footers and stabilization guy wiring, as well as detailing out our reinforced tower design through finite element analysis, said Tom Pinder, Western U.S. and Heavy Haul sales manager with Acrow. Additionally, the footprint allowed at the bottom where the tower footers were placed was very restrictive, and the set distance between the towers for each side was eccentric, and not centered for the bridge support as they normally would be.
Bill Killeen, president and CEO of Acrow Bridge, said, As the Mamalahoa Highway installation demonstrates, Acrow modular detour bridges are durable, easy to assemble, disassemble, transport, store, and customize. As temporary bridges that can be rented or purchased, they are a logical choice for state DOTs, and contractors use them to stay on or ahead of schedule and control costs, while providing a safe and dependable route for local residents and area businesses.
In another temporary application, two bridges over Manchester Brook in Ryegate, Vt., are enabling uninterrupted vehicular and rail traffic during culvert replacement. Acrows temporary bridges are expected to be in use until the completion of the project, which is currently anticipated to be June 2016.
The existing culverts, which will be removed and replaced, were hydraulically inadequate. Prone to clogging, they became blocked during Tropical Storm Irene in 2011 and required emergency repairs. The project implements a long-planned permanent solution by the Vermont Agency of Transportation to improve hydraulic capacity and provide a 100-year service life.
Acrow engineers and field staff worked with engineers from Dubois & King, Inc. and contractor Engineers Construction to install the two bridges, which allow for traffic flow to be uninterrupted for the duration of the project. The vehicular bridge, which is 80 feet long and 30 feet wide, carries two lanes of traffic on U.S. Route 5. Without the temporary structure, traffic including emergency vehicles, school buses, and trucks serving a nearby paper mill would have been greatly inconvenienced by road closures. The railroad bridge, which is 70 feet long and carries one rail line, ensures that freight traffic will not face unacceptably long detours if the line were shut for months or longer.
Although extreme weather complicated the installations many days were minus 15 degrees Fahrenheit the bridges were able to be opened on time, and in the case of the railroad bridge, completed around a single weekend traffic suspension, said Randy Needham, New England Region manager for Acrow Bridge.
A permanent, 80-foot-long Acrow steel bridge was completed on Ely Street over Bear Creek in Hannibal, Mo. The existing structure was found to be structurally deficient at inspection and had been closed since February.
The city purchased the bridge after it was determined that repairs to the severely rusting structure would last no longer than three to five years. Acrows prefabricated bridge was built to the citys specifications with a length of 80 feet and a width of 18 feet, with an additional 8-foot lane for pedestrian and bicycle traffic cantilevered off one side.
With the next nearest crossing two miles away, the bridge closing displaced not only residents and commuters, but the many tourists who visit the attractions in Mark Twains boyhood hometown and drive the scenic 50 Miles of Art corridor along the nearby Mississippi River, said Jeff Simkins, Midwest Regional manager, Acrow Bridge. The necessity for a rapid replacement required a compressed schedule from notice of purchase to shipment of components 20 calendar days for engineering and coordination of delivery.
Upon approval from the Hannibal City Council, Acrow Bridge was brought on by project engineers Poepping, Stone, Bach & Associates. Structural components arrived on site on June 6, and the bridge was assembled and installed by public works employees. Despite a two-week delay due to flooding, the bridge was opened ahead of schedule on Aug. 15.
The modular design of Acrow bridges make them a perfect choice when a cost-effective and rapid permanent bridging solution is needed, said Killeen. Customizable components can be engineered for many applications, have an estimated life span of 75 to 100 years, and are virtually maintenance-free.
Information provided by Acrow Bridge (www.acrow.com).