Four generations of unibody steel clamp anchors for posttensioning carbon-fiber-reinforced polymer (CFRP) rods were tested. Geometric properties of the anchors and the number of bolts providing the clamping force for a CFRP rod of nominal 3/8 in. (9.5 mm) diameter were varied. The anchors performed better with increasing number of bolts and anchor length and thickness. Finite element models provided a comparison of the contact pressure between the anchors and the CFRP rod. The generation IV anchors provided the highest contact pressure while controlling stress concentrations at the lead (load) edge. The four-bolt and three-bolt versions had similar capacities with an average efficiency of 126% based on the manufacturer-specified ultimate strength of the CFRP rod.
