Determination of design moments in bridges constructed with a movable scaffolding system (MSS)

This paper introduces simple but effective equations to calculate the dead load and tendon moments in concrete box-girder bridges constructed with a movable scaffolding system (MSS). Through time-dependent analyses of concrete box-girder bridges considering the construction sequence and creep deformation of concrete, structural responses related to the member forces are reviewed. On the basis of the compatibility condition and equilibrium equation at every construction stage, basic equations that can describe the moment variation with time in movable scaffolding construction are derived. These equations are then extended to take into account the moment variation according to changes in the construction steps. By using the introduced relations, the design moment and its variation over time can easily be obtained with only the elastic analysis results and without additional time-dependent analyses considering the construction sequences. In addition, the design moments determined by the introduced equations are compared with the results from a rigorous numerical analysis with the objective of establishing the relative efficiencies of the introduced equations.