Design moment variations in bridges constructed using a balanced cantilever method

Abstract

This paper introduces simple, but effective, equations to calculate the dead load and cantilever tendon moments in reinforced concrete (RC) bridges constructed using the balanced cantilever method (FCM). Through time-dependent analyses of RC 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 which can describe the moment variation with time in balanced cantilever construction are derived. These 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.