Numerical study and design of T-type branch plate-to-circular hollow section connections

A numerical finite element parametric study is presented on the behaviour of transverse or longitudinal T-type plate-to-CHS connections loaded under branch plate tension or compression, to evaluate the suitability of current international design recommendations and the effect of boundary conditions and chord length on such connections. Finite element modelling and analysis techniques used in the parametric study were validated by comparison with previously tested experimental results. A total of 120 connections with wide-ranging values of geometric properties were modeled and analyzed using commercially available software. An analysis of the effect of chord length determined that, to exclude the influence of chord end boundary conditions, an effective chord length of at least eight times and four times the chord diameter, for thin and thick walled chords respectively, should be used for experimental and numerical studies. Evaluation of current CIDECT partial design strength functions (Qu) indicated general conservatism and under-utilization of branch tension-only connection capacity. Partial design strength functions, determined through regression analysis of numerical finite element results and existing international experimental data, are hence proposed with lower bound reduction (resistance) factors.

► Improved design method for branch plate-to-circular hollow section T-connections.
► Branch compression and tension loading treated differently, which benefits the latter.
► Number of limit state design checks reduced from 2 (in current design methods) to 1.
► Application range of design method is wider than in present design guidelines.