Bond-Slip Relationships of Wires Used in Pretensioned Concrete Railroad Ties
KSU developed special wire testing frames and procedures to measure bond-slip performance of prestressing wires (or strands) in concrete. The test called for applying tension to the wires prior to casting the concrete and then slowly releasing the prestress force into the concrete. Forces and displacements were measured to control the test and develop the results. The results revealed significant variations in the bond-slip relationships for different wires, despite sharing the same diameter and tensile strength. These differences were attributed to both the wire indent characteristics and the amount of concrete surrounding the wire. This research also found a strong correlation between the bond-slip results and the force transfer length in pretensioned concrete prisms with similar wires. These methods and results are useful inputs to the concrete tie design process.