Non-linear component-based modelling strategy for beam-to-column steel-concrete composite joints under seismic loads

This paper proposes and validates a computationally efficient, non-linear numerical macro-modelling strategy to predict and assess the global and local response of steel-concrete composite joints, when subjected to seismic loads. The reference numerical model takes the form of a component-based strategy in which each component can be efficiently characterized in resistance and stiffness terms, and each constituent material has a typical non-linear behaviour with hysteresis (Takeda model for concrete, Pivot model the T-stub components and kinematic model for all the other steel members). The major advantage is the possibility to adapt the same unified modelling strategy to different configurations of steel-concrete composite joints, which may differ for geometrical and mechanical configurations of constituent members, position of joint (i.e., interior or exterior), connection type (welded or bolted), etc. As shown, due to the presented modelling approach, even under simplified assumptions, a rather close agreement is generally found between the present numerical predictions and the cyclic response of a selection of three different steel-concrete composite joints of literature, which have been investigated on full-scale experimental configurations. Most importantly, the contribution of steel members and the concrete slab can be efficiently taken into account, and allow to develop the typical mechanisms in which the slab itself is involved for the complex performance of composite frames under seismic events.