Realistic long-term prediction of prestress forces in PSC box girder bridges

The purpose of the present paper is to propose a method to give a more accu rate prediction of time-dependent prestress force changes due to creep and shrinkage of concrete in prestressed concrete (PSC) structures. Updating of long-term prediction of prestress forces is achieved using Bayesian statis tical inference. By Bayesian statistics, prior predictions of time-dependen t effects due to creep and shrinkage of concrete are used with the informat ion obtained from in-site measurements to develop updated predictions, or p osterior predictions. The prior prediction contains the uncertainties with regard to creep and shrinkage of concrete. The present study also deals wit h the uncertainties in the long-term prediction of creep and shrinkage effe cts using a sampling method. The proposed theory is applied to long-term pr ediction of prestress forces of an actual PSC box girder bridge. The presen t study indicates that the width of mean +/- two standard deviation for pos terior predictions of prestress forces with nine measurement information is about half that of mean +/- two standard deviation for prior predictions o f prestress forces. Therefore, the present numerical results prove that a m ore accurate long-term prediction of prestress force changes in PSC structu res due to creep and shrinkage of concrete can be achieved by employing the proposed method.