ANCHORAGE OF REINFORCING BARS FOR SEISMIC FORCES

High intensity cyclic loading tests are reported for 13 stub cantilever specimens. Bond conditions for the tensile reinforcement in those specimens were presumed to simulate conditions for beam bars in beam-column connections. Variables were the loading history for the bar, its surface geometry and its end anchorage. Except for fully reversed loading, failure occurred when the displacement at the "attack" end reached that for failure under monotonically increasing load. For fully reversed loading bond deterioration decreased the stiffness, reduced the "attack" displacement for failure and caused bars terminating in standard 180 degree hooks to have resistances dependent only on their "lead-in" lengths. Once slip penetrated the complete anchorage length, capacities on reversal of loading were negligible. Statistical formulas are developed relating the penetration of slip along the bar and energy absorption to the test variables. A simple geometric model is developed verifying the form of those formulas and identifying quantities required where variables differ from those of the test program.