Abstract
Prediction of damage is important in estimating the dynamic response analysis for reinforced concrete structures subjected to earthquake excitations. Damage prediction is usually measured in term of ductility factor, however, a combination of maximum displacement response and cumulative fatigue damage may cause to fail. In order to investigate low-cycle fatigue damage in RC columns, 7 reinforced concrete frames with rigid beams were tested by using a dynamic actuator. From the results of the test reported in this work, it is concluded that : 1) All specimens collapsed due to considerable degradation of axial load carrying capacity which occured after the shear compression failure at the head or knee of specimen and buckling of compressive longitudinal reinforcing bars. 2) The collapse of concrete structures with axial load is defined explicitly as sudden increase of cumulative axial displacement. 3) The rate of cumulative axial displacement dδ_v/dn can be expressed in the form dδ_v/dn=C △δ^α_T, where C and α are member constants, as shown in Fig.19. The Wohler curve can be obtained from this differential equation. 4) The Wohler curve for the lateral displacement amplitude △δ_T and average area △E of hysteresis loops can be shown as Eq. (3) and Eq. (6), respectively. The latter has a high correlation to experimental results. 5) The linear cumulative fatigue damage hypothesis is not true for low-cycle fatigue of reinforced concrete columns. 6) The non-linear cumulative fatigue damage ratio for reinforced concrete columns can be expressed in the form of Eq. (17) and (18).
