Experiment and design investigation of a multi-planar joint in a transmission tower

This paper focuses on a multi-planar steel tubular joint, which is in the slope change position of a new transmission tower. This slope change joint (SCJ) had six branch tubes and five chords in total, which led to complex interaction in the joint behaviour. To achieve experimental loading, a three-dimensional setup was designed for this joint. Detailed information of this SCJ and the test equipment were introduced. Then numerical model was established and validated by test results. Stress conditions of primary members, failure modes, influencing factors of the ultimate load as well as load transmission path were investigated by taking advantage of numerical analysis. Furthermore, a criterion for joint capacity was established referring to steel structure standards in different countries. Based on the established criterion, critical members were revealed and strengthened. In the end, procedures to optimize critical members and recommendations for joint design were proposed. Results proved that this SCJ can well meet the strength requirements after optimization.