Non-linear torsion behaviour of concrete filled steel tube columns

In curved girder bridge and skew bridge structures, due to the inconsistent locations of the mass and stiffness centres, nonlinear torsion effects will be produced in the piers. In order to study the non-linear mechanical behaviour of concrete filled steel tube columns subjected to combined compression–bending–torsion loads, the finite element method, suitable material constitutive equations, boundary conditions and combined load conditions were chosen and applied, and a three-dimensional “solid-shell” model for concrete filled steel tube columns was established. A good agreement was observed between the predicted results and test results, showing that the three-dimensional “solid-shell” model had high solution precisions, and comprehensive results for concrete filled steel tubes subjected to torsion could be obtained. The torsion mechanism of concrete filled steel tube columns was discussed in detail, based on results extracted from finite element models. Finally, a time-history analysis of a curved girder bridge using the finite element model was carried out, and the precision and effectiveness of the three-dimensional “solid-shell” model was fully verified for predicting the deformation and internal force of piers.