Seismic behaviour of dissipative beam‐to‐column steel and steel‐concrete composite joints

The present paper deals with the seismic behaviour of bolted steel and steel‐concrete composite partial‐strength beam‐to‐column joints with endplate connections. In a series of experiments in total 12 two‐sided internal joint specimens were tested, of which 3 were all‐steel and 9 steel‐concrete composite. For those, 5 parameters were varied, (i) thickness of endplate t_ep, (ii) vertical distance of T‐stub bolt rows e₄, (iii) distance of first shear stud to face of the endplate l, (iv) reinforcement ratio of concrete slab ρ and (v) number of bolt rows. The design of the specimens was performed with the help of both the component model as given in EN 1993‐1‐8 and a FEM model. The chosen parameter values were optimised to provide, for given beam and column sections, an upper and lower limit regarding moment capacity and rotational stiffness, for sufficient energy dissipation and ductility. The experimental results show that the stiffness of the concrete slab leads to a significantly different response of composite compared to all‐steel joints, especially regarding rotational stiffness and capacity of the joint as well as flexural stiffness of the (composite) beams. The composite joints present an overall better seismic behaviour compared to all‐steel ones.