ABSTRACT
The UHPC (ultra-high-performance concrete) composite box girder consists of three segments of UHPC U-shaped girder, 50 mm UHPC depth deck plate and reinforced high-strength concrete (HSC) slab with 240 mm depth. The steel fiber 1.5% of volume fraction was added to the UHPC mixture to induce ductile behavior in the girder. The webs and deck plate of the box girder are not reinforced in the longitudinal direction and no stirrups. Totally 146 tendons inserted in upper and lower flanges of girder to induce flexural strength of composite box girder. Moreover, FBG (fiber bragg grating) sensors are used in lower flange to monitor stress-strain relationship of tendons. The objective of this study is to calculate the instantaneous prestress loss and compare it to the results of experiment and finite element analysis of 50 m UHPC post-tensioned composite box girder. The finite element analysis was used as a strong analytical tool for modeling of UHPC composite box girder. The commercial version of MIDAS FEA was used. The difference in instantaneous loss of tendons between analytical calculation and experimental result are 2-9%. The analytical calculation and FEA show good agreement with experimental result.
