Development of Ductile Bridge Columns with Enhanced Flexural and Shear Incore Zone

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Based on a series of shake table experiments for a full-size bridge column using E-Defense, it was found that crushed core concrete spilled out from steel cage under extreme excitations. Such a failure model was first identified based on a full-model column excitation. It is anticipated that this failure modes accelerate degradation of column failure. Since such a scale-effect has not been sufficiently studied in the past due to limitation of large experimental facilities, the scale effect on the failure mechanism at the plastic hinge was investigated in this study. Four 5/36 geometrical scale models which were design and constructed as close to the full-size model as possible were exposed to the same response displacement and varying axial load after they were scaled-down based on the similarity law. It was found that both 1) an evaluation of sectional areas of deformed bars which have difference diameters and shape of surface deformation and 2) the maximum aggregate size were important for identifying the scale effect. It was found that progress of damage was faster in the full-size model that the scaled models though the flexural capacity can be well predicted by the scaled-model. Since the level of excitation to the full-size column by E-Defense was not extreme enough to develop collapse, it was found based on the study that under extremely strong excitation, the scaled models have a large limitation for predicting the failure mechanism of full-size columns.