Finite-Element Analysis of Shear-Off Failure of Keyed Dry Joints in Precast Concrete Segmental Bridges

The structural behavior of precast concrete segmental bridges largely depends on the behavior of the joints between segments. The current practice of precast concrete segmental bridges is to use small keys that are usually unreinforced, normally dry, and distributed over the height of the web and the flange of concrete segments. In this study, a numerical analysis model was established based on finite-element code to investigate structural behavior of keyed dry joints under direct shear. The concrete damage plasticity model along with the pseudodamping scheme were incorporated to analyze the system for microcracks and to stabilize the solution, respectively. The numerical model was calibrated by full-scale experimental results described in the literature. It was found that the predicted ultimate load, cracking evolution history, and final crack pattern agreed reasonably well with experimental results. The validated numerical model was then used for parametric study on factors affecting shear behavior of keyed dry joints, in this case confining pressure. The authors found that shear capacity predicted by the AASHTO code equation diverges from that predicted by numerical analysis at high confining pressure, because the contribution of friction in the total shear capacity decreased with an increase in confining pressure. Hence, the authors recommend reducing the friction coefficient used in the AASHTO code equation when high confining pressure is applied. Moreover, the propagation of inclined crack was arrested at high confining pressure owing to the fact that the fracture propagation direction is governed by the criterion of the maximum energy release rate.