Parametric study of tubular KK multiplanar steel connections

This paper presents a parametric study of symmetrically loaded multiplanar KK connections in circular hollow steel sections. The connections were designed with gaps between the diagonal braces. Analyses were performed using the commercial finite element program Ansys. A total of 54 KK connections and their corresponding uniplanar K connections were analyzed and compared in terms of the connection resistance. A new objective criterion to assess the two failure modes most often occurring in KK connections is proposed. Failure mode 1 is observed when two neighboring diagonal braces loaded in the same sense act as one brace penetrating the chord together. In failure mode 2, excessive deformation is observed in the chord region between two neighboring braces, folding the chord wall. However, in some cases, the failure mode is not easily identified, or both failure types are present. The proposed criterion is based on the diametric deformation of the chord and objectively assesses the failure mode. By comparing the connection resistance of KK and K connections as determined using numerical analyses, analytical expressions to predict the connection resistance of KK connections were developed. The expressions accurately predict the connection resistance based on geometric parameters and the resistance of the corresponding uniplanar K connection.