Analysis and modelling of CFT members: Moment curvature analysis

Abstract

The evaluation of the ultimate behaviour of Concrete Filled Tubular (CFT) members subjected to non-uniform bending moment is the main objective of this work. To this aim eight experimental tests have been performed at the Materials and Structures Laboratory of the Department of Civil Engineering of Salerno University. In particular, Square Hollow Section (SHS) CFT members have been investigated under monotonic loading conditions. The three point bending scheme is adopted for testing specimens, where an hydraulic actuator is used for the transmission of the transverse load at midspan under displacement control and an LVDT is used to measure the corresponding maximum transverse displacement. In addition, longitudinal deformations along the cross section perimeter have been measured by means of strain gauges, aiming to the experimental evaluation of moment–curvature relationship.This paper presents the structural details of the tested specimens and the corresponding experimental results. In addition, a fibre model able to predict the ultimate response of CFT members is also presented and compared with the experimental results. The presented fibre model accounts for all the effects influencing the ultimate behaviour of composite members, such as local buckling, confining effects on concrete, bi-axial stress state of the steel plate elements constituting the hollow profile and hardening of its corners due to cold forming process.The comparison between experimental and numerical results shows a good agreement pointing out the accuracy of the proposed fibre model.