CYCLIC BEHAVIOR OF MODERATELY DEEP HSC BEAMS

The experimental investigations of moderately deep high-strength concr ete beams subjected to various imposed inelastic cyclic deformations a re presented. Fifteen cantilever beams having cross section of 200 x 4 00 mm were reinforced in accordance with the seismic design provisions of the current building code (ACI 318-89). An additional two normal-s trength concrete beams were tested as reference specimens. The test va riables included: (1) Shear span-to-depth ratio; (2) ratio of longitud inal reinforcement at top and bottom; and (3) loading histories. The c yclic performances of beams were evaluated in terms of the characteris tics of strength and stiffness degradation and energy-dissipation capa city. The behavior of plastic hinges was also studied. Test results re vealed that moderately deep HSC beams were able to resist the various cyclic loads to a displacement ductility factor of 3 to 4. For the loa ding histories considered in this study, the specimens exhibited prono unced decay in both strength and flexural stiffness when they were loa ded beyond a displacement ductility factor of 3. Under cyclic loads, m oderately deep HSC beams exhibited less spalling in the plastic-hinge zone, which led to slower strength degradation and better energy-dissi pation capability than did the normal-strength concrete beams.