Plastic collapse of longitudinal T-type branch plate-to-CHS connections under compression

Nowadays, longitudinal branch plates are used as structural members in several engineering applications to connect brace members to Circular Hollow Section (CHS) chord members, which are widely employed due to their aesthetical appeal and efficiency. At ultimate limit state, the failure mechanism of T-type branch plate-to-CHS connections is characterized mainly by the formation of yield lines in the chord. This paper presents an analytical methodology developed using the yield line approach to predict the compressive strength of the longitudinal T-type branch connections. A numerical finite element parametric model was developed and calibrated with experimental work from literature to accurately assess the joint capacity in different configurations. Results obtained from the proposed analytical model show very good agreement with the calibrated FE model. Moreover, a comparison between the results of the parametric FE analysis with both previous studies and current design guidelines is presented. The proposed analytical model takes into consideration the most influential geometrical parameters and the effect of membrane stresses, which was found to be significant in slender chord members. The newly proposed equation also considers the slenderness of chord members which is not considered in the current design equations.