Analytical model for the response of T-stub joint component under impact loading

• Experimental and numerical studies to evaluate the non-linear behaviour of a T-stub component exposed to impact loads
• Simplified Smodel to evaluate the plastic resistance of a T-stub component exposed to impact loads
• Incremental analytical model to characterise the non-linear behaviour of a T-stub component exposed to impact loads
• The strain rate effect on the material constitutive law is demonstrated in the enhancement on the force-displacement response.
• With the increase of the strain rate, less ductile failure modes are activated.

Accidental loadings due to blast or impact may easily cause failure of the elements exposed or located in the vicinity of the hazard; therefore, assessment of the structural over strength is critical for structural engineers to ensure a certain level of security and validate alternative unloading paths. The importance of the ductility of connections has been highlighted for the robustness evaluation of structures in FEMA's report “Connection performance under impact loads… needs to be analytically understood and quantified for improved design capabilities and performance as critical components in structural frames”. The design of moment-resisting steel joints under monotonic loading is based on the “component method” (Eurocode 3, Part 1.8). This method requires the accurate characterisation of each active component; T-stub model is used to describe the main components providing ductility to the joint due to its high deformation capacity. However, connection ductility capacity characterisation remains problematic, usually requiring the development of challenging finite-element models.In this paper, the T-stub evaluation is supplemented with dynamic increase factors to predict the response of T-stubs subject to rapidly applied dynamic loads. Firstly, based on the methodology established in the Eurocode, Part 1.8, a “dynamic” design resistance is calculated; secondly, by exploring and improving an analytical procedure available in the literature, its whole non-linear behaviour is described. The analytical results are compared with 3D FE predictions and experimental results. This “modified analytical procedure” was demonstrated to be able to describe the force-displacement response of the T-stub model for both static and dynamic situations with relevant accuracy.