Development of a numerical model for load transfer mechanism in grouted post-tensioned tendons

This research describes the development of a numerical model that captures the load transfer mechanism in grouted post tensioned tendons due to breaking of corroded wires. The approach is based on developing a finite element (FE) model for the tendon and modeling the interaction between the steel strand and the grout. The surface interaction is modeled based on a surface based cohesive behavior. This behavior depends on a user defined stiffness (K) matrix which accounts for the adhesion between the interfaces. The stiffness value constants are calibrated in order to match the results of an experimental program conducted on a seven grouted strand. The simulations are carried out by the commercial finite element Abaqus software. The experimental results indicated that the fractured strands are observed to re-anchor along the length of the model and the grout provides the only available mechanism for redistribution of tensile stresses among strands under axial loading. Although broken strands are able to recover load, the overall load carrying capacity of the strand decreases over time. Numerical results demonstrate that the load recovery capacity in the strands varies with different parameters, such as number of broken strands, cohesive stiffness (K) values, and the length of the tendon. Significant loads from the broken strand are transferred to surrounding strands by cohesion mechanism between the strand-grout interfaces. The analysis of results also shows that the strands close to break, carry more loads than more distant strands. The results from the numerical modeling showed excellent agreement with available experimental results.