Abstract
The method of strengthening by means of external tendons has been adopted to handle situations where prestressing is insufficient. The external tendons are anchored to the anchorage units attached to the main girder web. The anchorage units consist of concrete brackets; friction grip connections bound to the web using prestressing bars are used. Based on the principles of fastening force and friction coefficient (friction resistance), the design is conducted so as to ensure a constant safety factor with respect to sliding. In this study, tests were conducted for these factors using cast-in-place concrete anchorage units of a type frequently used in recent years, with make-up procedure. Actual size test specimens were fabricated using the actual construction procedure. As a result, it was demonstrated that anchorage unit joint interfaces treated with sandblasting or water jetting are sufficiently integrated to function against horizontal loads. With inclination within the 12 degrees permitted in specification, the fastening force is not decreased in case of appropriate surface roughness, and sufficient fracture strength can be demonstrated. Furthermore, it was demonstrated that this tendency continued in sliding after fracture.
