Modelling of a Novel Lead Damper and Application to an Existing RC Structure

The work presents a novel Prestressed LEad Damper with Straight Shaft (PS-LED), which incorporates several desirable characteristics, namely high stiffness and damping capability in a compact design, and low manufacturing cost, which make it suitable for social housing. The device provides a resistive force by the friction activated between a lead core and a shaft, showing a consistent rigid-plastic behavior without significant strength degradation; the shape of the hysteresis loops is essentially rectangular, resulting in an equivalent damping ratio of 0.55. A modelling procedure is suggested to represent in the OpenSees framework the non-linear behavior of the PS-LED for both static and dynamic analyses. In particular, for dynamic analyses, a finite element object of the PS-LED is formulated by means of a simple rheological model comprising a parallel of a non-linear spring and a viscous model. In order to show the effectiveness of the PS-LED device for the retrofit of reinforced concrete structures, a case-study is chosen as paradigmatic of a category of existing buildings in Italy designed according to outdated codes. The structure is retrofitted with the PS-LED in order to maintain an elastic behavior, with no plastic hinges, during the earthquake. Non-linear static analyses are performed on the upgraded building, showing a fair agreement between the design target and the actual performance. To provide a deeper insight, bidirectional non-linear dynamic analyses are further performed considering a suite of artificial bidirectional ground motions in accordance with the provisions of the Eurocode 8.