Abstract
Since the 1990s, new types of seismic-resistant building and bridge structural systems have been designed that use unbounded post-tensioning tendons. The entire post-tensioning force is transferred at the tendon anchorages in these structures. This experimental study investigates the use of unbounded post-tensioning strand-anchorage systems subjected to different loading conditions. The experiments investigate the strand stresses and strains at wire fracture inside the anchors, considering initial stress, loading rate, eccentricity between the strand ends, and post-yield cyclic loading. Results showed that post-yield cyclic loading is the parameter that most consistently reduces the average wire fracture strains of strand-anchorage systems and should be used in the validation testing of unbonded post-tensioning strand-anchorage systems for extreme seismic applications. Updated stress-strain relationships are proposed for 0.5-in.-diameter and 0.6-in.-diameter strands that provide a separate stress-strain relationship for each diameter as well as a combined one for both diameters. Directions for future research are discussed.
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