03.13: Experimental study on cyclic plastic behaviour of steel joint components

Civil engineering structures are subjected to enormous cyclic forces during a seismic event. Designing structures with dissipative zones provides an efficient solution to withstand these seismic forces. The zones, which dissipate energy through plastification, can be designated parts of the structural skeleton, or special, sacrificable elements that built into the structure. An economical way to increase the dissipative capacity of a structure is to utilize the cyclic plasticity of the connections. The local ductility of these structural connections is sensitive to their arrangement and requires a careful design. The large number of available connection types prohibits any comprehensive treatment of dissipate zones on the connection level; however, it is feasible to make generalizable observations on the component level, which can support engineers to design connections with sufficient plastic capacity. As part of an ongoing research program, an extended cyclic experimental campaign is completed on 51 specimens, related to three important joint components: (i) T‐butt weld and T‐fillet weld; (ii) single and double‐sided lap joints; (iii) bolted T‐stub. These components are subjected to monotonic and cyclic loading by increasing and constant load amplitudes. In the T‐butt weld and T‐fillet weld tests the effect of the load direction and throat thickness are analysed. The lap joint and bolted T‐stub experiments are focused on the effect of cyclic plasticity and cyclic degradation types of failure modes. The low‐cyclic fatigue response of the investigated components are evaluated, and the critical mechanisms, which influence the energy dissipation, are identified. Based on the experimental study design recommendations can be developed which can be used to increase the local ductility of the investigated joints.