In recent years, the U.S. Army Corps of Engineers has launched major developments in underwater construction of locks and dams, using the so-called "in-the-wet" or "offsite prefabrication" construction method. This innovative method uses precast concrete modules as the in situ form into which tremie concrete or other infill material is placed directly without use of a cofferdam. The tremie concrete is designed to work in composite action with the precast concrete modules. Numerous in-depth investigations have been conducted by several Corps districts and their consultants to evaluate the feasibility of the in-the-wet method at various potential sites of U.S. inland waterways. These studies have shown that the innovative construction method can provide substantial benefits in cost, construction time, risk reduction, and facility utilization, while minimizing disruption to river traffic and reducing environmental impact.

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This manual is intended to serve as a reference. It will provide technical information which will enable Manual users to perform the following activities:Describe typical erection practices for girder bridge superstructures and recognize critical construction stagesDiscuss typical practices for evaluating structural stability of girder bridge superstructures during early stages of erection and throughout bridge constructionExplain the basic concepts of stability and why it is important in bridge erection* Explain common techniques for performing advanced stability analysis along with their advantages and limitationsDescribe how differing construction sequences effect superstructure stabilityBe able to select appropriate loads, load combinations, and load factors for use in analyzing superstructure components during constructionBe able to analyze bridge members at various stages of erection* Develop erection plans that are safe and economical, and know what information is required and should be a part of those plansDescribe the differences between local, member and global (system) stability