Non-Linear Behaviour of Steel-Concrete Composite Moment Resisting Frames

Steel-concrete composite framed buildings are highly efficient structural systems due to their stiffness, strength and ductility. Such systems allow also adequate seismic performance nevertheless their application in seismic area is prevented by the lack of experimental information and design rules, especially about joints. The present work focuses on the seismic design and assessment of a typical steel and concrete composite multi-story moment-resisting frame, with 4 stories. The provisions implemented in European standards and guidelines are applied and discussed especially when uncertainties about their application come out; in fact a number of such provisions are not straightforward and/or reliable and further improvements are deemed necessary. After the frame has been designed by a linear analysis, a series of non-linear pushover analyses are performed by a lumped plasticity model introducing different models for the beam-column joint and plastic hinge length. In particular, since the definition of the plastic rotation capacity is not univocally defined, the formulations available for steel or reinforced concrete structures are discussed and evaluated also. The results are synthesized in terms of q-factor in order to assess the values suggests by the international codes.