A study of anchorage capacities of confined bent-bar reinforcement

Abstract

Some of the factors which influence the anchorage capacities of bent deformed reinforcing bars in joints of reinforced concrete structures were examined. Ten full scale specimens simulating an exterior beam-column joint in a structure were tested in order to evaluate the anchorage capacity of the beam bars subjected to varying degrees of confinement and bent to different geometric configurations. High strength deformed bars (ASTM A-615 Grade 6) with diameter of 7/8" were used in the tests. The hooks that were used, both 9° and 18, conformed to ACI specifications and recommendations. The following types of confinement were studied: a) longitudinal column bars; b) column ties through the joint ranging from none to #3 bars @ 2.5"; c) concrete cover Axial forces ranged from 27 kips to 55 kips. The experimental program consisted primarily of measuring the slip between the bent deformed reinforcing bar and concrete at three points and the strains on the reinforcing bars at three points also, at all the load stages until the failure of the specimen. The influence of the different variables considered on the anchorage capacity of the bent deformed reinforcing bars was discussed.