Vertical cracking at girder ends during post‐tensioning of prefabricated prestress concrete bridge T‐girders

Abstract

AbstractPrefabricated post‐tensioned pre‐stress concrete (PC) T‐girder is one of the common structural forms for bridge superstructure to achieve better quality control, higher construction speed and lower downtime to the transportation system. However, vertical cracks are frequently observed at the web of girder ends after prestress is applied, which could impose an adverse effect on the durability of girders when exposed to aggressive environment. In this paper, the mechanism of this cracking pattern and corresponding countermeasures were investigated by a numerical study as well as practical engineering applications. To begin with, a nonlinear three‐dimensional (3D) finite element model was developed to simulate a typical PC T‐girder in the platform of ABAQUS. The model was loaded based on the sequence of post‐tensioning. It was found that the vertical crack pattern is caused by the large friction resistance and bond strength at the contact surface between the girder and supporting steel pedestal as well as the stress concentration at the girder ends due to the cambering effect of girder during the application of prestress. In addition, a practical method was proposed to control this crack pattern by introducing an isolation cushion made of a thin wood piece to the bottom of girder end. The reliability of this method was verified by numerical analysis and engineering practice. Therefore, it can be used to control vertical cracks at the ends of prefabricated post‐tensioned PC bridge T‐girders during construction.