Long-Term Behavior of an Eccentrically Loaded Inclined CFST Mega-Column in a 400-m-Class Supertall Building

Accurate prediction of the long-term deformation of inclined concrete-filled steel tubular (CFST) mega-columns in supertall buildings remains challenging because concrete shrinkage and creep interact with load eccentricity, confinement, and steel–concrete interface behavior. Existing long-term studies have mainly focused on concentrically loaded CFST members and rarely consider these effects within a unified numerical framework. This study adopts an eccentricity-dependent confined-concrete model developed in our previous work and incorporates time-dependent shrinkage and creep strains into a member-level ABAQUS analysis. The finite element model solves the structural response at successive increments, while the creep subroutine uses a reference strain stored during the loading stage. The numerical results are compared with two shrinkage tests and two creep tests reported in the literature and are then used in engineering case studies of CFST members in a supertall building. Because the available tests cover limited parameters and observation periods, the longer-term engineering results are interpreted as model-based predictions. For the L16-D1761 reference member, the shrinkage-only, creep-only, and combined shrinkage–creep strains at approximately one year are about 76, 34, and 110 με, respectively. At approximately 350 days, the compression-side strain increases from about 1.10 × 10−4 under concentric loading to about 1.94 × 10−4 at an eccentricity ratio of 0.625. Increasing the steel–concrete interface friction coefficient reduces the predicted long-term deformation, although its influence on the subsequent deformation growth rate gradually decreases with time. These results demonstrate the importance of jointly considering shrinkage, creep, eccentric loading, and interface interaction in member-level long-term assessment of inclined CFST mega-columns.