Retrieval of True Lateral Load–Deformation Behavior of Axially Loaded Columns from Experimental Data

Abstract

The lateral load-deformation capacity of any structure is the most important aspect of seismic design. The lateral capacity of a shear building is highly dependent on the lateral load-deformation capacity of the columns, which is usually evaluated by considering a cantilever column of half the length of the actual one on the basis of a symmetric double-curvature deformation profile. The test setup for cantilever columns under the action of axial and lateral loads might alter the true cantilever behavior due to the fixing arrangement of actuator heads at the free end of the column–effectively making that end not free. In this paper, a mechanics-oriented approach to rectification, with appropriate nonlinear constitutive models for a column, is proposed to eliminate the effects of fixing actuator heads and changes in actuators’ axial directions in order to obtain the true cantilever behavior of the column. The proposed methodology is verified using monotonic and cyclic experimental data beyond yielding. It is found that the aforementioned effects can be quite significant for high axial load or large lateral displacement, which, if not eliminated, may lead to a mistaken estimation of the lateral capacity of a cantilever column. It is further observed that if the true cantilever behavior is not captured, the calibrated material model parameters (to match the experimental load-deformation curves) for a cantilever column will deviate from the actual ones due to overadjustment.