Shrinkage cracking at interior supports of continuous pre-cast pre-stressed concrete girder bridges

Abstract

This study deals with the control of cracking at interior supports of continuous pre-cast pre-stressed concrete (PCS) girder bridges. Since PCS-girder bridges are constructed by placing in-situ concrete decks on the PCS-girders at time intervals, the differences in material properties and age at loading between the deck and girder lead to time-dependent material behaviors. In addition, the continuous deck by providing a negative moment connection at interior supports, also causes the transverse cracking of the concrete deck at interior supports. In that way, cracking at interior supports is predicted with the analytical model introduced in the companion paper. Based on the ACI model, the ultimate shrinkage strain is expressed as a function of concrete slump and the relative humidity while the other remaining factors such as unit weight of cement and air content are assumed, in accordance with the typical values in mixed concrete. Finally, field recommendations in terms of concrete slump and relative humidity are suggested to minimize early transverse cracking of concrete decks at interior supports.