A Survey on Patch Loading Models for Bridge Launching

During the incremental launching of steel and composite bridges high support reactions have to be introduced into the slender steel webs of the bridge girder. In the past, the specific characteristics of bridge launching such as long loading lengths and longitudinal stiffeners were not covered appropriately by existing design formulae for patch loading. In the frame of the research project “Competitive Steel and Composite Bridges by Improved Steel Plated Structures (COMBRI)” a clear improvement of the patch loading resistances for I-girders and box sections could be derived leading to more economic solutions for this type of loading. The paper introduces the basic concepts of the developed models for both unstiffened girders and girders with open-section and closed-section longitudinal stiffeners as well as a software tool for the advanced determination of elastic critical buckling loads and modes. A comparison of the main area of application and the resulting economic advantages concludes the survey.