CYCLIC BEHAVIOR OF MODERATELY DEEP HSC BEAMS

The experimental investigations of moderately deep high-strength concrete beams subjected to various imposed inelastic cyclic deformations are presented. Fifteen cantilever beams having cross section of 200 x 400 mm were reinforced in accordance with the seismic design provisions of the current building code (ACI 318-89). An additional two normal-strength concrete beams were tested as reference specimens. The test variables included: (1) Shear span-to-depth ratio; (2) ratio of longitudinal reinforcement at top and bottom; and (3) loading histories. The cyclic performances of beams were evaluated in terms of the characteristics of strength and stiffness degradation and energy-dissipation capacity. The behavior of plastic hinges was also studied. Test results revealed that moderately deep HSC beams were able to resist the various cyclic loads to a displacement ductility factor of 3 to 4. For the loading histories considered in this study, the specimens exhibited pronounced decay in both strength and flexural stiffness when they were loaded beyond a displacement ductility factor of 3. Under cyclic loads, moderately deep HSC beams exhibited less spalling in the plastic-hinge zone, which led to slower strength degradation and better energy-dissipation capability than did the normal-strength concrete beams.