New moment-resisting beam-column joints to increase progressive collapse resistance of precast concrete buildings

Abstract

Since existing precast RC (reinforced concrete) structures are lacking structural continuity at regions of beam-column connections, they are less resistant to progressive collapse in the event of column removal than CIS (cast-in-situ) RC structures. The prime objectives of current research are to revise the existing precast simple shear beam-column connections and to develop new precast moment connections for increasing the progressive collapse robustness of precast buildings. To achieve these goals, 11 half-scale beam-column assemblies – comprising two beams and three columns – were numerically investigated under the middle column removal scenario using nonlinear 3D FE (finite element) modeling. Two specimens represented typical existing precast simple beam-column connections, and three specimens had revised precast simple connections. Four assemblies were designed with new precast moment connections. The last two specimens represented CIS concrete beam-column connections with continuous and discontinuous longitudinal beam bars to be compared with the precast assemblies. The FE modeling incorporated strain rate-dependent nonlinear constitutive models, contact between different parts in the connection region, and bond-slip at steel bars-to-concrete interface. As a key outcome of this research, the newly developed precast moment connection with the highest rotational ductility was recommended for diminishing the potential of progressive collapse in precast concrete buildings.