Mitigation of seismic risk on high-rise buildings using rocking cores

Rocking systems consist of structures, or portions thereof, properly designed to oscillate at the base when subjected to ground motion excitations. The mitigation of the seismic risk is achieved by shifting the natural period of the fixed-base structure, which, in turns, provides a reduction of the seismic loads induced in the superstructure. This work investigates the performance of a multi-story steel frame with inner rocking braced core. This latter system includes viscous dampers, designed to provide effective dissipative behavior and mounted between the foundation and column bases. The benefits produced by the introduction of this novel protection system for withstanding severe ground motion excitations are discussed via numerical examples. The seismic performance of the integrated system with rocking core is compared with the mechanical behavior of a fixed-base building to evaluate its efficiency in alleviating severe damage. Response spectrum and time history analyses are performed. Long duration, standard and pulse-like records are considered to appreciate how different energy contents of the ground motion affect the seismic response of the building structure.