Long-Term Prestress Loss and Camber of Box-Girder Bridge

The evaluation of long-term prestress losses and camber, taking into account the effect of creep, shrinkage, and relaxation, is essential for prestressed concrete bridges. An effort has been made in this paper to identibr a suitable time-dependent creep coefficient and shrinkage strain models to estimate the long-term prestress losses and camber for an existing box-girder bridge span. Longterm prestress losses and camber are estimated using four different models for creep and shrinkage-ACI 209R-92, CEB MC90-99, GL2000, and B3-and the comparison has been made with field measurements. From the limited studies made, it is seen that for the initial 5 years after the construction of a bridge, the B3 model can be used for estimation of long-term losses, and the CEB MC90-99 model can be used for estimation of long-term camber However; for a prestressed concrete beam, the ACI 209R-92 model is found to predict closer prestress loss values with laboratory measurements.