Method for calculating local bearing capacity of concrete under bond stress from reinforcement in straight anchor section

Abstract

A pull-out test is performed on 30 concrete specimens to determine the effect of bond stress on the local bearing capacity. The parameters include the dimensions of the headed bars, strength grade of the concrete, embedded length of the reinforcement, and diameter of the reinforcement. The dimensions of the headed bars are 50 mm × 50 mm × 20 mm and 60 mm × 60 mm × 20 mm, and the strength grades of concrete are C30, C40, and C50. The diameters of the reinforcement are 25 mm and 32 mm and its embedded length is divided into five types in the test. The local bearing capacities of 30 concrete specimens are obtained, and three failure modes are observed in specimens. The different modes of failure primarily depend on the combined action of the shell structure and wedge of the concrete. The pull-out test results indicate that the local bearing capacity of concrete under headed bars increases with an increase in the embedded length of reinforcement and the strength grade of concrete, with an almost linear relationship. In addition, the local bearing capacity decreases with an increase in the relative protective-layer thickness of the concrete specimens. Finally, a calculation method is proposed for the local bearing capacity of concrete under the action of bond stress from the reinforcement in a straight anchor section. The calculations considered the relative embedded length and the relative protective layer thickness of concrete as independent variables and the ratio of the local bearing capacity of concrete to the bearing capacity of concrete under the headed bars as a dependent variable. This calculation method provides a theoretical basis for standard revision and engineering applications.