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 200×400mm 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.