Stress concentration factors of cold-formed stainless steel tubular X-joints

This paper describes experimental and numerical investigations on stress concentration factors (SCFs) of cold-formed stainless steel square and rectangular hollow section (SHS and RHS) tubular X-joints. Both high strength stainless steel (duplex and high strength austenitic) and normal strength stainless steel (AISI 304) specimens were investigated. The SCFs were experimentally determined under static loading by measuring the strains at typical hot spot locations using strip strain gauges. The corresponding finite element analysis was performed to simulate the non-uniform stress distribution along the brace and chord intersection region. Good agreement between the experimental and finite element analysis results was achieved. Therefore, an extensive parametric study was then carried out by using the verified finite element model to evaluate the effects of the SCFs of cold-formed stainless steel tubular X-joints. The SCFs at the hot spot locations obtained from the experimental investigation and parametric study were compared with those calculated using the design formulae given in the CIDECT for carbon steel tubular X-joints. It is shown from the comparison that the design rules for the SCFs specified in the CIDECT are generally quite unconservative for cold-formed stainless steel tubular X-joints. In this study, a unified design equation for the SCFs of cold-formed stainless steel tubular X-joints is proposed. The proposed design equation was based on the CIDECT design equation for carbon steel tubular X-joints. It is shown that the SCFs calculated from the proposed unified design equation are generally in agreement with the values predicted from finite element analysis. © 2013 Elsevier Ltd. All rights reserved.