Parametric analysis and design equation of ultimate capacity for unstiffened,overlapped CHS K-joints

A finite element model simulating the experiment on unstiffened,overlapped CHS K-joints was generated and validated by comparing the ultimate capacity,deformation process and failure mode with experimental results.Using this model,the stress distribution,propagation of plasticity and the failure mode of overlapped joint with through-brace-in-compression and welded hidden seam were studied.The effect of geometric parameters,with or without hidden weld,and loading hierarchy reversal of braces on the ultimate capacity of the joints was also studied.The results of FE parametric analysis indicate that brace-to-chord thickness ratio has relatively large effect on the failure mechanism and ultimate capacity of overlapped joints;the absence of hidden welds has less significance on the ultimate capacity of the through-brace-in-compression joint than on that of through-brace-in-tension joint.Finally,based on the design equation of gap joint,a formula predicting the ultimate capacity of overlapped CHS Kjoint was proposed by applying multivariate regression analysis.Results calculated using the proposed design equation agree well with experimental results.