Development of Efficient Anchorage Device and Estimation of Its Bearing Strength of Posttensioning Anchorage Zone

The posttensioning anchorage system of prestressed concrete consists of an anchorage device and lateral reinforcements for the enhancement of the concrete surrounding the anchorage device. In this paper, experimental and analytical studies were conducted in order to develop an efficient anchorage device and to design an equation of the bearing strength in the posttensioning anchorage zone. Eighteen load transfer specimens were tested, and the results were compared with the AASHTO and National Cooperative Highway Research Program (NCHRP) equations to investigate how they estimated the ultimate resisting capacity of the anchorage zone. The finite-element model for the numerical analyses was verified by comparison with the test results. Three-dimensional nonlinear analyses were carried out for the three design variables: (1) the location, (2) the length, and (3) the number of ribs used to evaluate the effect of each variable on the bearing strength. The best efficiency of the anchorage device was shown when a rib was placed at the opposite end of the bearing plate or when two ribs were evenly placed over the anchorage device. From the results of the parametric studies, the modified bearing capacity equation that implied the effect of additional transverse ribs was suggested.