Dynamic behaviour of coupled soil-structure systems by means of FEM analysis for the seismic risk mitigation of INGV building in Catania (Italy)

Abstract

Seismic design of new structures, as well as retrofitting and/or improving of existing ones should be definitely considered a multidisciplinary subject, which depends on many factors, such as: local site effects and the dynamic interaction between the foundation soil and the structure. The accurate investigation on the structure and the surrounding soil is the first fundamental step for a realistic evaluation of the structure seismic performance. The present paper deals with the Dynamic Soil Structure Interaction (DSSI) analysis concerning the INGV (National Institute of Geophysics and Volcanology) building in Catania, by means of a FEM 2D modeling. The building is a prestigious masonry structure situated in an area characterized by a high seismic hazard. Several accelerograms scaled at the same PHA, with reference to the estimated seismicity of Catania, have been adopted. Soil properties were carefully investigated by means of static and dynamic in-situ and laboratory tests. Many investigations were also performed on the structure. Equivalent linear visco-elastic constitutive models have been adopted both for the soil and the structure. For considering soil nonlinearity, degraded shear modula (G) and increased soil damping ratios (D) have been evaluated for all the involved soil layers, according to two different approaches. Firstly, soil nonlinearity has been modeled basing on the EC8 [2003] suggestions; secondly, it has been modeled choosing the values of G and D according to the effective strain levels obtained for each soil layer and for each different input, by means of an iterative sub-routine. The dynamic response of the system has been analyzed in the time and frequency domains. Results are presented in terms of: acceleration amplification factors, Fourier and response spectra, amplification functions and shear forces per floor. The main goals of the paper are: i) to investigate the acceleration profiles along the soil and the structure considering and not considering the DSSI; ii) to investigate the soil filtering effect in terms of predominant frequency considering and not considering the DSSI; iii) to compare the obtained results with the ones given by a simpler 1D free-field soil analysis; iv) to compare the soil amplification factors and the response spectra obtained by 1D and 2D models with that by the Italian technical code [NTC, 2008]; v) to highlight the influence of DSSI in the seismic response of the structure; vi) to evaluate the influence of different modeling of soil nonlinearity on the dynamic response of the soil and structure.

Nonlinear 3D Finite Element Analysis of a Coupled Soil–Structure System by a Deterministic Approach

“…In this case, the period elongation has positive effects, since the frequency of the structure, f STRU,SSI , tends to shift from the resulting frequencies for the SSI condition and from the predominant frequencies of the input motion. Similar considerations were also formulated by Massimino et al [8].…”

“…Many recent seismic events, such as the 2009 L'Aquila earthquake, the 2010 Haiti earthquake and the 2016 Norcia earthquake, show the importance of considering the SSI effects for the safeguarding of existing structures or for the planning of new ones [7]. Indeed, the kinematic and inertial interactions between the soil, the foundation and the structure modify the dynamic response at the foundation level [8]. The following two main approaches can be employed to evaluate the SSI effects: the "substructure method" and the "direct method".…”

“…Most of the studies on SSI effects employ the equivalent visco-elastic constitutive model, which involves carrying out a series of linear analyses with subsequent updating of the stiffness and damping parameters until a convergence criterion is satisfied [10]. Massimino et al [8] evaluated the seismic response of a soil-building system by means of the ADINA code using the equivalent visco-elastic constitutive model. Seylabi et al [11] investigated the capabilities of calibrated equivalent linear models in capturing the dynamic response of buried box structures.…”