ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/296997
A C C E L E R AT E D B R I D G E C O N S T R U C T I O N As owners look to save costs and erect bridges faster with less interference to the traveling public, the concepts of sliding and rolling bridges transversely into place after constructing them nearby are becoming more popular. These techniques offer benefits, but they require unique considerations that can make the difference between success and failure. Both design and construction teams must understand these movement considerations. Sliding or rolling bridges into place has become accepted by contractors due to the tighter time restrictions owners are placing on projects and their awareness of user costs for tying up either roadway access or waterways. These approaches also can help minimize environmental impact during and after construction. In some cases, owners require this delivery method in their contract documents, necessitating designers and contractors to become familiar with the techniques as soon as they can. In these cases, clients often want to avoid employing cranes on small sites, which create economic drawbacks. On the plus side, owners don't typically provide detailed requirements for how the bridge should be moved into place. When they do, they often allow contractors to propose alternatives, ensuring the most efficient approach can be employed. There are three typical options when considering how to move bridges into place: • Pushing with hydraulic jacks on rollers or pads • Pulling with hydraulic jacks or cables on rollers or pads • Moving with self-propelled modular transporters (SPMTs) This article and the next in the ASPIRE™ accelerated bridge construction (ABC) series will deal with design issues of the first two types, sliding or rolling the components into place. These will be followed by a look at necessary activities in the field during construction. The use of SPMTs will be addressed in a subsequent article. Define Duties Because few companies have deep experience with these projects yet, it is critical for engineers and contractors to define each member's duties, requirements and who will be responsible for all the means and methods. Typically, the means and methods will derive from the contractor's preference, based on the method with which the contractor is most comfortable. In creating a construction plan, the design team should develop an ABC strategy with requirements for as-builts or contingency by Craig A. Shutt Sliding and Rolling Bridge Solutions–Part 1 As used on the I-80 bridges over Echo Dam Road in Echo, Utah, the slide shoes on the bottom of the abutment wall glide across polytetrafluorethylene (PTFE) pads onto the permanent abutment. Photo: Michael Baker Jr. Inc. ASPIRE , Winter 2013 | 21 AspireBook_Win13.indb 21 12/28/12 11:39 AM