Seismic behaviour of beam-to-column partial-strength joints for steel–concrete composite frames

The paper presents a large experimental campaign carried out on ten steel–concrete composite beam-to-column sub-assemblages employing monotonic and cyclic loading test protocols. Structural members (beams, columns and slabs) were defined through the design of a full-scale 3D prototype frame subjected to PSD testing campaign; main design hypothesis was to dissipate seismic energy in the joints designed as partial-strength. Testing programme on beam-to-column sub-assemblages was executed in order to assess seismic performance varying structural details at beam-to-column connection level and material qualities. Different mechanical connecting systems between concrete slab and column, two end-plate configurations, weak and strong column web panel, two steel qualities and different concrete strengths.The analysis of sub-assemblages performance was realized in two steps: a first step in which the joints behaviour was assessed, characterizing response at local level (e.g. moment–rotation curves); a second step in which the response was assessed at global level (e.g. force–displacement curves). The structural behaviour (i.e. resistance, plastic deformation and stiffness) was evaluated at three stages–identified as initial, service and maximum load–in order to monitor the evolution of sub-assemblage response increasing solicitation level. Moreover, seismic behaviour of specimens–in terms of dissipated energy, ductility, over-strength and equivalent viscous damping–was also executed. Comparison between experimental results was made in order to identify those parameter suitable for improved and reliable seismic behaviour of steel–concrete composite partial-strength joints.