Effect of Vibrating Buildings on Free-Field Motion and on Adjacent Structures: The Bonefro (Italy) Case History

During the 2002 Molise sequence, a shock was recorded in a building that suffered heavy damage (Mucciarelli et al., 2004). The availability of this data, along with other similar data, led to the organization of an international workshop for structural engineers aimed at the reproduction of the staged evolution of damage observed (A. Goretti and M. Mucciarelli, unpublished manuscript, 2007). The aim of this present work is to model the damaged building; the adjacent, less damaged building; and a large section of the subsoil. The model should provide some insight into two possible phenomena: (1) the soil–structure interaction (SSI), that is, the modification of the free-field seismic response induced by the presence of the buildings located on soft soil; and (2) the possible interaction between the two buildings. The study was performed using the 2D Chebyshev spectral element method (SPEM) for a 2D section. The model, with topography, includes the bedrock (limestone) with the overlaying clay layer, circa 30 m. The building is modeled by an equivalent shearwave velocity, which is calculated from its identified mechanical properties. First, the model’s ability to reproduce the motions recorded inside and outside the building was verified. Then, one or both of the buildings were removed to study their effect. The influence of the presence of buildings on the free-field motion is about 40% on spectral values, and it is felt up to a distance of about 250 m from the buildings. The results also suggest the presence of resonance between buildings.