NUMERICAL EVALUATION OF SPLITTING PERFORMANCE OF PRESTRESSED CONCRETE PRISMS WITH LARGER DIAMETER PRESTRESSING WIRES

摘要

This numerical study focuses on evaluating the structural performance of prestressed concrete prisms with larger diameter (0.315 in) prestressing wires. More commonly used prestressing wires are the 0.209 in (5.32 mm) diameter wires for prestressed concrete crossties. However, there has been an interest to adopt larger diameter prestressing wires in order to provide higher prestress forces with the aim of mitigating the structural damage of prestressed concrete crossties. Previous experimental studies demonstrated that small-scale pretensioned concrete prisms had excellent correlation in bonding performance of concrete ties pretensioned with 0.209 in (5.32 mm) wires or three- or seven-wire strands. Using a finite element (FE) modeling approach, this study investigates the effects of 8 mm diameter prestressing wires on the splitting/bursting performance of prisms at the onset of de-tensioning of the wires. The studied parameters include geometrical/mechanical parameters such as thickness of the concrete cover, spacing between the wires, level of prestress forces, and concrete release strength in compression. Cohesive elements with a newly developed nonlinear bond-slip model are assigned to the interface between the prestressing wires and the surrounding concrete. The parameters for the bond-slip model are calibrated based on a simple pull-out test on concrete cylinders with the 0.315 in (8 mm) diameter wires. The simulation results are compared with the predicted splitting performance of prisms pretensioned with 0.209 in (5.32 mm) wires or seven-wire strands. Based on the FE analysis results, recommendations are made on the minimum concrete cover thickness and wire spacing required to achieve acceptable splitting/bursting performance in prestressed concrete prisms.