Analytical and Measured Strains in Sunshine Skyway Bridge. II

This paper presents a methodology for the analysis of stage-constructed prestressed-concrete bridges. The method uses the step-by-step superposition of strains and accounts for time-dependent effects including creep, shrinkage, and hardening of concrete and relaxation of prestressing steel. This analytical model has been developed as a synthesis of structural analyses and computations of time-dependent deformations. The predicted strains in the pylons show reasonable agreement with the measured time-dependent strains. The magnitudes of the predicted time-dependent strains in the box-girder segments, including the thermal effects, closely agree with the measured values. Time-dependent deformation relationships are derived for the strain variations for the pylon and segment erection sequence. The analytical model can be used to predict the behavior at any specified time during the construction stages. The methodology is demonstrated with a 10-yr prediction of the time-dependent strains by superposition of the effects of forces and moments resulting from the construction sequence.