Analysis and calculation method for concrete-encased CFST columns under eccentric compression

This paper presents a computational method for concrete-encased concrete-filled steel tube (CFST) columns under eccentric compression, which adopts the form of equivalent rectangular stress integrated by material constitutive curve. When establishing finite element model via ABAQUS, confinement provided by stirrup was considered to modify the constitutive law of encased concrete, so that the numerical modeling was in good agreement with tests. By analyzing the simulation results, the applicability of basic assumptions, such as plane section assumption, was discussed, and a database of 207 models with various parameters was created. The developed method took into account the influences of geometric nonlinearities of section shape, and its accuracy was verified against various collected tests and the database. It turned out that the formula presented was applicable to a wide range and had sufficient precision, while the predictions of N -M interaction curves of concrete-encased CFST columns in EC4, AISC and CECS were conservative due to the ignorance of the exact integration about irregular section-shape.