Dissipating and re-centring devices for portal-frame precast structures

The seismic response of buildings not specifically designed to resist earthquake actions can be generally improved by allowing the structure to dissipate an appropriate amount of energy. The use of passive devices for improving the seismic performance of precast concrete structures is investigated herein. In industrial and commercial precast concrete buildings, these devices can be successfully applied at the beam-to-column connections of hinged portal-frames, in order to increase the connection degree of fixity and the dissipated energy during a seismic event. The specific aspects and efficiency of passive dissipation devices based on rotational friction with and without the addition of a re-centring device is analyzed herein. Such devices may be applied both to existing and new buildings; indeed, they are able to mitigate the inter-storey drift demand, to limit the damage at the column base and to reduce residual drifts. A design procedure is developed in the paper for portal-frames implementing the investigated devices. A case study representing a single-storey precast concrete portal-frame is selected. The design procedure is applied to the case study, considering various devices configurations. The structural performance is assessed by means of non-linear time history analyses.