On the behaviour of diagonally-stiffened concrete-filled steel tube-to-SHS steel brace T-joints: An experimental and numerical investigation

Abstract

In this paper, the behaviour of the T-joint between concrete filled-steel tube (CFST) chord members with diagonal PBL (Perfobond Leiste) stiffeners and square hollow section (SHS) steel braces is investigated. First, seven T-joint specimens were prepared and experimentally tested under axial load of the steel brace. The results were analysed and discussed with respect to the failure modes, load-displacement responses and load-strain curves. Obviously, the diagonal PBL stiffeners were found to effectively limit the cracking range of concrete, thereby improving the bearing capacity of the T-joints. This is followed by a finite element (FE) analysis for the T-joints using ABAQUS software. FE models were validated using the test results and then parametric studies were generated. These studies included the effects of the ratio of brace-to-chord width ($\beta$), the ratio of brace-to-chord thickness ($\tau$), the position and thickness of the PBL stiffeners and the steel and confined concrete material grades. Based on the experimental and numerical results, the bending characteristics were obtained for the steel brace-CFST chord T-joint under the axially compressed steel tube brace. Furthermore, the accuracy of the Chinese, Japanese, American and European specifications to calculate the bending bearing capacity of the T-joints were checked, and the results yielded highly conservative results. Therefore, a new calculation method was currently proposed, which takes into account the strengthening effect of the brace on the upper flange of the chord. The comparisons showed that the obtained results of this proposed method are in good agreement with experimental and FE results, and therefore can safely and reliably be used in design.