抄録
Many experimental results have shown that splitting bond failure is the complicated phenomenon governed by many factors such as concrete cover, bar locations in a cross section, concrete strength, development length and transverse reinforcement. The purposes of this paper are to clarify the mechanism of splitting bond failure of deformed bars and to evaluate quantitatively the influences of decisive factors upon bond capacities. Main factors chosen as test variables in this study were; number, diameter and location of main bars in a cross section, and spacing, diameter and yield strength of enclosing stirrups. Tests were conducted using catilever type specimens. Based on the test results it was derived that the significant role of stirrups in bond resistance was to change the failure mode more ductile rather than to increase the ultimate strength. When appropriate stirrups were provided, the bond resistance was maintained even after concrete splitting, to allow large slip at and after peak bond stress. Using the authors' previous test data on the specimens without stirrups, the effects of stirrups on splitting bond strength were discussed. The effect of stirrups was dependent on the geometrical arrangement of longitudinal bars and stirrups in a cross section, in other words, on the splitting patterns. The use of high strength steel for stirrups was not effective to improve the bond strength. Taking account of these effects, the empirical equations for splitting bond strength were derived, which successfully described the test results. In Part 2 of this paper, the developed equations are extended to more generalized forms and verified from the applications to many test data of other investigators.
