Deflection monitoring of cast in-situ balanced cantilever prestressed concrete box girder bridge

Abstract

Monitoring of deflection in the construction of a long span segmental balanced cantilever prestressed concrete box girder bridge is very important because bridge deflection will affect the final bridge level and to avoid large level discrepancies during the joining of two cantilevers. This study presents a comparison of actual and design short-term deflection considering the effect of creep for a four span balanced cantilever prestressed concrete box girder bridge. Each span consists of 26 segments and the deflection data were obtained using leveling instruments. The actual concrete strength of the segments were also recorded. Analysis using these data and the local creep coefficient were carried out using ADAPT-ABI software. Comparisons between actual and design deflections indicate that they are similar for the first four segments of each span with very small values. Substantial values of deflection begin to develop at the fifth segment and the critical value occurred at the middle of the cantilever span. It is also observed that the deflection values are inversely proportional to the concrete strength but directly proportional to the creep coefficient. As an extension of this study, further investigations can be carried out on long term deflection of concrete box girder bridge, behaviour of box girder bridge due to temperature difference, effect of varying element thicknesses and early loading.