Behavior of Deficient Joints with Plain Bars and Low-Strength Concrete

Two series of tests of exterior beam-column joints were conducted. In the first series of tests, the longitudinal reinforcement of the beam was anchored in the joint with 90-degree hooks. In the second series, hooks of top bars were welded to hooks of bottom bars. Parameters varied from one test to the next and included axial load, amount of joint reinforcement, and displacement history. All of the test specimens were fabricated using low-strength concrete and plain bars to represent the conditions of joints of existing deficient reinforced concrete building structures. The test results indicate that the strengths of the specimens in Series I were limited by the slip of beam reinforcement at its anchorage. While the lateral load resistance of the specimens in Series 2 was higher, the nominal capacities of the column and the beam were not reached because of the combined effects of shear and slip of bars in the joint. Despite the observed damage, all of the specimens sustained their capacity to carry lateral loads during static displacement reversals with maximum drift ratios up to 4%.