Behavior and Design of Unbonded Post-Tensioning Strand/Anchorage Systems for Seismic Applications

This thesis presents an experimental study on the ultimate stresses and strains of unbonded post-tensioning (PT) strands at wire fracture inside an anchor. The research includes the following strand/anchor configuration parameters: (1) strand diameter; (2) anchor type [cast and barrel type anchors] and physical properties; (3) number of anchor wedges [2-piece and 3-piece wedges]; and (4) presence of a binding ring around the wedges. Additionally, the following loading parameters are investigated: (1) loading rate; (2) eccentricity between the strand ends; (3) post-yield cyclic loading; and (4) initial strand stress [i.e., prestress]. The test results are used to make design recommendations and to evaluate strand/anchor configurations that may provide better strand ductility. It is shown that seismic loading can cause a significant reduction in the strand strains at fracture and an increase in the variation of the fracture strains. Industry requirements for the validation testing of strand/anchorage systems are assessed.