Time dependent deformation in prestressed concrete girder : measurement and prediction

Synopsis

Prestressed concrete girders which are intended for composite construction in bridges and other similar structures are often stored unloaded jar some time before being placed in their final positions where top deck is being poured over.
During that free storage the girders are subjected to creep and shrinkage which manifests itself through increased upward deformation usually defined as camber. The analytical estimation of this deformation is important as it controls the minimum thickness of the top deck. If this deformation is exagerated, then this requires increase of the top deck and possible change in the level of bridge surface. The estimation of creep deformation is made generally in a single step calculation using data from applicable standards.
In this paper an attempt was made to correlate on site measurements with continuous computer modelling of the time-dependent behaviour using data from recently adopted international standard for concrete structures. It was found that computer modelling does predict faithfully the general behaviour of the girder. However, data from the herein used international standard is exaggerated for local conditions, so that the completed camber was larger than the measured one.