Numerical assessment of slab-interaction effects on the behaviour of steel-concrete composite joints

In this paper, the possibility of realizing a composite joint that behaves as moment-resisting under gravitational loads and essentially as hinged under horizontal loads is investigated. Aiming to assess the actual slab-interaction effects on the overall response, a full 3D Finite Element (FE) model representative of a beam-to-column composite joint taking part of a braced frame is described in ABAQUS and validated towards past full-scale experiments. A parametric study is hence proposed, by accounting for three geometrical configurations, being characterized by (i) isolated slab with absence of rebar continuity (i.e. fully disconnected slab and steel joint only), (ii) presence of slab with partial column interaction (i.e. isolated slab and continuity of rebar), (iii) presence of fully interacting slab. It is shown that, if properly detailed, a joint with isolated slab and continuous rebars can be used in non-braced spans of composite braced frames without affecting the behaviour of the bracing system (i.e. as in presence of a hinge). Nonetheless, the composite beam can be designed as continuous on multiple supports under vertical loads, hence leading to a reduction of the steel cross-sectional size.