External steel bracing frames with energy dissipation devices for the seismic retrofit of a precast R.C. school building

Abstract

This study presents a retrofit solution for a school building located in a high seismic risk area. The as-built structure, composed of precast concrete elements, lacks sufficient strength to meet the seismic and gravitational load requirements set by the Italian Building Code.

The proposed intervention includes the installation of external steel braced frames equipped with energy-dissipating devices. These frames increase the building’s stiffness, thereby reducing displacements of structural elements. The corresponding increase in acceleration is offset by the dissipation of seismic energy through the installed devices.

The positioning of the steel frames along the building perimeter is chosen to regularize seismic behavior by minimizing the eccentricity between the center of mass and the center of rigidity, thereby reducing the resulting torsional effects.

In addition, local strengthening interventions are proposed, like those increasing the shear strength of beams and establishing a mechanical connection between the precast beams and columns, whose current interaction relies solely on friction.