Taking into consideration the dynamic interaction between structure and foundation soil is generally recognized to allow a beneficial reduction in the forces acting on the superstructure, since the natural period of superstructure plus foundation soil is longer than that of its fixedbase counterpart. An additional beneficial contribution is given by plastic strains developing in the “near field” causing a not negligible reduction in the energetic content of the input. The paper examines, in case of embedded foundations, the effects of removing the lateral ground on the dynamic soil-structure interaction. The proposed lateral disconnection produces a change in both the stiffness and the damping ratio of the overall system. It also causes a parasite effect: a shrinkage of the foundation interaction domains and an increase in base rotations. All these factors are taken into account in the paper and a procedure is presented to design the trenches to be excavated. A parametric analysis is carried out by varying (i) the dimensions of the lateral disconnection; (ii) the stiffness of the soil. The obtained results are presented and discussed in the paper, focusing on the effectiveness of the proposed lateral disconnection. In a series of specific cases, it is demonstrated that a proper selection of the lateral disconnection width allows a suitable increase in the natural period of the soil-structure system significantly reducing the seismic actions on the superstructure, so improving the performance of existing buildings under seismic conditions.
SEISMIC BEHAVIOUR OF LATERALLY DISCONNECTED SHALLOW FOUNDATIONS
Orazio Casablanca;
2019-01-01
Abstract
Taking into consideration the dynamic interaction between structure and foundation soil is generally recognized to allow a beneficial reduction in the forces acting on the superstructure, since the natural period of superstructure plus foundation soil is longer than that of its fixedbase counterpart. An additional beneficial contribution is given by plastic strains developing in the “near field” causing a not negligible reduction in the energetic content of the input. The paper examines, in case of embedded foundations, the effects of removing the lateral ground on the dynamic soil-structure interaction. The proposed lateral disconnection produces a change in both the stiffness and the damping ratio of the overall system. It also causes a parasite effect: a shrinkage of the foundation interaction domains and an increase in base rotations. All these factors are taken into account in the paper and a procedure is presented to design the trenches to be excavated. A parametric analysis is carried out by varying (i) the dimensions of the lateral disconnection; (ii) the stiffness of the soil. The obtained results are presented and discussed in the paper, focusing on the effectiveness of the proposed lateral disconnection. In a series of specific cases, it is demonstrated that a proper selection of the lateral disconnection width allows a suitable increase in the natural period of the soil-structure system significantly reducing the seismic actions on the superstructure, so improving the performance of existing buildings under seismic conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
