Strength and ductility of concrete-filled tubular piers of integral bridges

In this paper, an analysis of the structural response of concrete-filled tubular columns (CFT) when subjected to combined bending and compression is presented. The reference frame of the study is the usage of such members as piers of integral bridges. The main objective of the study is to assess both the resistance and the ductility of these structural elements when subjected to lateral displacements. These displacements, together with the corresponding axial forces, represent actions to which the integral bridges piers might be subjected to. For the sake of studying this response, a numerical model is used as a simulation tool over a hypothetical matrix of CFT with realistic proportions. A parametric study is undertaken to monitor the influence of the steel contribution- and the length-to-diameter ratios on the strength and ductility of the CFT. These numerical studies together with a wide experimental database found in the literature have been useful for drawing conclusions concerning these topics. A design proposal concerning the cross-sectional capacity of the CFT, based on the studies performed by other researchers which accounts for confinement, is provided. This proposal has been compared with the present EN1994 formulation. In addition, design formulae which might characterize the ductility of the CFT in terms of the maximum allowable lateral displacements are provided for non-slender CFT piers of integral bridges.