Numerical investigation for the behaviour of stiffened circular concrete filled double tube columns

Abstract

Concrete filled double tube (CFDT) columns are considered effective to be used in heavy loaded structures, such as bridges, subway stations, and skyscrapers owing to the numerous advantages of concrete filled steel tube (CFST) columns. This paper aimed to numerically study the performance of CFDT columns under concentric loads and present innovative strengthening methods for CFDT columns, which yield more load bearing capacity compared to the existing ones. The proposed stiffened CFDT column will meet the requirements for use in heavy loaded structures. Circular steel hollow sections have been used for the inner and outer tubes. Stiffeners with different profiles (rectangle, T and bar stiffeners) have been welded to the outer and inner tube to check their contribution in increasing the load capacity and enhancing the performance of the circular CFDT columns. The behaviour of CFDT columns is investigated numerically by using a verified finite element (FE) model from the ABAQUS program. Verification of the FE model is achieved by comparing the obtained results with previous test results. Several parameters have been investigated using the FE model. The result revealed that using stiffeners in CFDT Column has a significant effect in increasing its load capacity, which can be increased to more than 15% of its original capacity by increasing number of stiffener and decreasing its slenderness. Based on the parametric study design guide line is presented. A new simplified design model is proposed for the prediction of the axial load capacity of stiffened circular CFDT columns.