Experimental study on material properties and stress concentration factors of stainless-steel hybrid tubular joints

This paper presents an experimental investigation to determine the stress concentration factors (SCFs) of stainless-steel hybrid tubular joints, connecting circular hollow sections (CHSs) with square hollow sections (SHSs) under axial loads. Austenitic stainless-steel (AISI 304 grade) was used to manufacture all specimens. In total, twelve experiments were conducted comprising T, Y and X joints. To obtain the material properties of stainless-steel hybrid tubular joints, tensile coupon tests were conducted. For each joint, eight unidirectional strain gauges were placed to measure the hot spot strain perpendicular to the weld toe and the strain parallel to the weld toe. To analyze the strain gauge data from experiments, the hot spot stress method was used, adopting the quadratic extrapolation method, to determine the SCFs of stainless-steel hybrid tubular joints. From the results of experiments, strain concentration factors and conversion coefficients were recommended for stainless-steel hybrid tubular joints. The maximum SCFs recorded from the experiments on the SHS chord and CHS brace of stainless-steel hybrid tubular joints were then compared against the design values calculated in accordance with the CIDECT Guideline 8 and the proposed design formulas by Tong et al. and Yin et al. for carbon steel hybrid tubular joints. It is shown that the current design formulas as prescribed in CIDECT Guideline 8, are conservative by around 20%, while determining SCFs of such stainless-steel hybrid tubular joints.