Component Characterization of T-plug Bending Around Weak Axis

Abstract

Explicit rules for safety verification of open cold-formed lightweight beam-to-tubular column joints are missing in the current EC3-1-8. By developing economical detailing, with design guidance based on Eurocodes, the market share for new buildings, renovation and for additional storeys on existing buildings will increase. Within the INNO3DJOINTS project an innovative plug-and-play joint is developed, allowing for modularity and industrialization for low to mid-rise buildings. This solution will increase the competitiveness and sustainability of steel construction. The goal of this MSc thesis is to characterize the behaviour of the plug-and-play joint using the component test; T-plug bending around weak axis. The strength, stiffness and deformation capacity following the EC3-1-8 component method approach are investigated.

An experiment is designed for testing in the Stevin-II laboratory at Delft University of Technology. This work includes both the design of the set of test specimens and laboratory set-up. Secondly, a numerical study is performed to predict the experimental results and an extending parametric study is performed to derive new components, using the finite element software of ABAQUS. The influence of geometrical properties; thickness ratio (reverse channel vs. T-plug web), use of stiffeners, use of tubular sections and length of the T-plug web, is studied for a steel grade S355. The numerical study is validated for three configurations using the component test; T-plug in tension, provided by the INNO3DJOINTS project. As the parametric study is based on an elasto-plastic material model, these numerical results are directly used to derive new analytical expressions/models and characterize new components and component interactions for design verification. The numerical study resulted in the identification of seven active components for the plug-and-play joint, consisting of basic EC3-1-8 components and tubular components from the CIDECT report 16F: Component method for tubular joints. In addition, two new components are introduced namely, the reverse channel in bending and T-plug in bending. Based on a total of 127 unique joint configurations, new analytical expressions are derived to characterize the behaviour of the new components for resistance and stiffness. The component interaction is established by proposing a physical spring model and a component model suitable for Eurocode implementation. This results in the characterization of the joint behaviour for the experimental configuration C-SHS200 with a 7.5% deviation on the resistance and a 20.5% deviation on the stiffness compared to the numerical result. The accuracy of the joint stiffness can be improved if the component stiffness derivation also includes non-governing configurations and a wider range of parameters is studied, such as the position of the bolt holes along the net-section and the use of tubular section. The results, derivations and the physical spring model contribute to the INNO3DJOINTS project and could be used for implementation in the software tool, to be developed by the French Institute CTICM. Besides, the Eurocode aligned component model is recommended for practical use in design standards, but further research should be performed on the verification of the rotational stiffness on the joint level.