Numerical Investigations into the Seismic Behaviour of Free from Damage Joints

Abstract

The current strategy implemented in EN 1998 for designing buildings with resistance against seismic actions is based on capacity design principles. This method allows the formation of plastic hinges into predefined parts of the structure in the ultimate limit state, meaning there will be significant damage in critical elements of the structure. These current EC8 methods are cheap in construction, but cost a lot for rehabilitation after a seismic event. There is a need for new design strategies which improve the seismic response of structures while decreasing potential damage caused by a rare seismic event. In the last few decades, new design methodologies have been proposed for this purpose. Efficient systems for improving seismic resistance of a structure and for minimizing damage include: shear metal panels, BRBs, viscous dampers, replaceable shear links in EBFs, and friction dissipative joints. The last possibility of dissipative joints in structures is effective, efficient, and economical. Joints fitted with friction damping devices are not significantly larger or more costly than current seismic resisting joints. There will be no architectural interference from the friction damping device, and the cost of rehabilitating a structure fitted with such joints will be considerably reduced. This is due to the fact that FREEDAM joints dissipate energy through friction between plates in contact rather than through plastic deformation. The aim of the FREEDAM project is to develop seismically prequalified novel types of joints which dissipate seismic energy through friction. During both numerical and empirical tests, the cyclic behavior of these joints has proven to be stable with low degradation of strength and high rotational capacity. In this paper, the seismic behavior of FREEDAM joints is investigated using FEM methods to compare the response of a full frame fitted with FD joitns versus modern RBS joints, as well as to theoretically analyze several sub-configurations and assemblies within the FD2 joint configuration. The accuracy of assumptions made in the finite element models are also validated.

The current strategy implemented in EN 1998 for designing buildings with resistance against seismic actions is based on capacity design principles. This method allows the formation of plastic hinges into predefined parts of the structure in the ultimate limit state, meaning there will be significant damage in critical elements of the structure. These current EC8 methods are cheap in construction, but cost a lot for rehabilitation after a seismic event. There is a need for new design strategies which improve the seismic response of structures while decreasing potential damage caused by a rare seismic event. In the last few decades, new design methodologies have been proposed for this purpose. Efficient systems for improving seismic resistance of a structure and for minimizing damage include: shear metal panels, BRBs, viscous dampers, replaceable shear links in EBFs, and friction dissipative joints. The last possibility of dissipative joints in structures is effective, efficient, and economical. Joints fitted with friction damping devices are not significantly larger or more costly than current seismic resisting joints. There will be no architectural interference from the friction damping device, and the cost of rehabilitating a structure fitted with such joints will be considerably reduced. This is due to the fact that FREEDAM joints dissipate energy through friction between plates in contact rather than through plastic deformation. The aim of the FREEDAM project is to develop seismically prequalified novel types of joints which dissipate seismic energy through friction. During both numerical and empirical tests, the cyclic behavior of these joints has proven to be stable with low degradation of strength and high rotational capacity. In this paper, the seismic behavior of FREEDAM joints is investigated using FEM methods to compare the response of a full frame fitted with FD joitns versus modern RBS joints, as well as to theoretically analyze several sub-configurations and assemblies within the FD2 joint configuration. The accuracy of assumptions made in the finite element models are also validated.