Long-term Analyses of Concrete-Filled Steel TubularArches Accounting for Interval Uncertainty

Creep and shrinkage of the concrete core of a concrete-filled steel tubular (CFST) arch under sustained loading are inevitable, and cause a long-term change of the equilibrium configuration of the CFST arch. As the equilibrium configuration changes continuously, the long-term radial and axial displacements of the CFST arch, stress distributions as well as the internal forces in the steel tube and the concrete core change substantially with time. Creep and shrinkage of the concrete core are related to a number of its material parameters such as its creep coefficient, aging coefficient, and shrinkage strain. The values of these parameters differ significantly from one experiment to another, highlighting that these parameters experience certain amounts of uncertainty, which needs to be considered in the long-term analysis of a CFST arch. Although stochastic methods can be used to account for such uncertainties, their statistical variations are presumed being known, which have to be inferred from laboratory tests. However, the available data from creep and shrinkage tests of the concrete core of CFST members are quite limited and scattered, and so the stochastic method is of little use. This paper presents a long-term analysis of CFST circular arches by accounting for interval uncertainties in these parameters by interval modelling, and derives the upper and lower bounds for the long-term structural responses. It is shown that the uncertainties of creep and shrinkage of the concrete core have significant long-term effects on the structural behaviour of CFST arches.