NUMERICAL ANALYSIS OF CREEP AND SHRINKAGE IN HIGH-RISE CONCRETE OR STEEL-CONCRETE BUILDINGS

The expansion of concrete construction in high-rise buildings has made these structures sensitive to the effects of creep and shrinkage. Initial and time dependent strains of concrete generate both absolute and relative displacements in vertical elements that cannot be neglected. The problem is further complicated by the sequential character of high-rise construction involving continuous sequences of loading steps and changes of structural configurations. If these effects are not adequately understood and analyzed in design and construction phases, several serviceability concerns may arise, affecting structural members as well as non structural components. Ultimate safety may be influenced as well, as a result of delayed increases of axial loads in vertical elements. The paper presents a computational approach for the evaluation of these effects based on the combination of a finite element discretization of the structural configuration, with account for its evolving character and the sequence of loading steps, and of the recursive numerical algorithm for the solution of the hereditary integral problem induced by the adoption of a linear aging viscoelastic constitutive relation for creep. The proposed analysis procedure is applied to the time-dependent analysis of a case study relative to a multi-storey building.