Abstract
For the limit state design or the establishment of more reasonable design method on anchorage zone in posttensioned prestressed concrete members, the behavior in ultimate stage and the bearing strength of anchorage zone should be revealed. In the previous paper, proposed equations for estimating the bearing strength of anchorage zone with the combination of circular loading plate, circular loaded surface and circular reinforcement are induced and good result of examination of those equations with experimental date is shown. This paper describes the failure mechanism and bearing strength of anchorage zone consisted of square bearing plate, square loaded surface, circular spiral reinforcement and concrete with lower strength which will be generally used in partially prestressed concrete members. On the discussion based on the results of experiment reported herein in which the variables considered are area of bearing plate, amount of reinforcement, covering depth and concrete strength, following concluding remarks are obtained. 1) Two failure types observed in specimens used in this experiment are similar to those occured in specimens reported in the previous paper. The failure type I and II are characterized by the failure of concrete surrounded by the circular reinforcement and the failure of concrete underside of the core, respectively (see Figs.3 and 4). 2) Equations (7) and (9) for the estimation of bearing strength of specimens are deduced considering the amount of reinforcement, the ratio of area of bearing plate to that of anchoring surface and the covering depth of concrete (see Figs. 5〜7 and 9). 3) The examination of feasibility of induced equations shows that the experimental values of bearing strength are estimated succesfully for practical use in the range from 0.8 to 1.2 times values by the induced equations (see Figs. 12 and 13).
