Time-Dependent Deformations of Eccentrically Loaded Reinforced Concrete Columns

If reinforced concrete columns and walls in high-rise buildings are subjected to axial load for a sustained duration, long-term lateral deformation (or curvature) as well as axial shortening increase over time due to the creep and shrinkage of concrete. In the present study, sustained load tests were performed to evaluate the time-dependent axial shortening and lateral displacement occurring in eccentrically loaded columns. A test set-up using post-tensioning steel rods was introduced for the sustained loading with or without eccentricity. The test results showed that the lateral displacement as well as the axial shortening increased over the sustained duration but the increasing rate of the long-term deformations rapidly decreased with increasing time. The time-dependent axial shortening and lateral displacement increasing with time were predicted by using the age-adjusted effective modulus method based on the creep and shrinkage models of ACI 209. The predictions agreed well with the test results.