|Session 10.2 - Soil-structure Interaction|
Tanks are a critical part of seismic lifelines, providing water and fuel for the period immediately following an earthquake event. This paper focuses on a typical steel tank on soil of medium strength and describes an evaluation of the seismic loading and displacement of the foundation mat. Both the impulsive and convective modes of the tank are considered. An equivalent linear solution in the frequency domain is used. Radiation damping of the foundation soil is investigated. The influence of radiation damping is shown to be greater on the horizontal displacement of the tank compared to rotation. The overturning moment and horizontal shear on the foundation mat are significantly effected by the stiffness of the foundation soil. The yield acceleration of the mat foundation with respect to overturning and shear is evaluated. The elastic and plastic displacements of the foundation mat (rotation and translation) are evaluated using a Newmark sliding block analysis for the permanent deformation.
Keywords: tank foundation, earthquake loading, soil structure interaction
The purpose of this paper is to look at the provisions of the draft Australia-New Zealand loading standard (DR1170.4/PPCS3) with respect to the effect of soil-structure interaction on the earthquake design actions for shallow foundations supporting multi-storey buildings. Work by earlier researchers had led to the suggestion that for tall buildings the lengthening of the structure-foundation period caused by soil-structure interaction might give reduced foundation design actions. The results of numerical modelling using the modal response spectrum method did not reveal any strong evidence for such a reduction, in fact generally there was an increase rather than a decrease. We suggest that the jumps between the design spectra when moving from a rock site, to a shallow soil site, to a deep soil site are more significant than the subtle soil-structure interaction effects caused by the modest period lengthening of the structure-foundation system induced by the soil conditions considered.
Keywords: Australia - New Zealand Loading Standard, earthquake foundation design actions, soil-structure interaction, shallow foundations
The paper employs a coupling method to utilise finite elements and boundary elements, together with a bounding surface soil model, to investigate the amplification of a soft clay site, especially considering the effect of soil non-linearity. The ground surface responses from the analyses are then used as input motions to investigate the response of a fixed-base 6-storey frame. The analyses show that soil non-linearity has a large influence on the structural response due to site amplification in a period range around the fundamental period of the frame.
Keywords: Site amplification, structural response,non-linear soil, bounding surface model
Influence of Three-dimensional Soil-structure Interaction on Structural Responses Induced by Near-source Earthquakes
The study addresses the relationship between the characteristics of near-source earthquakes and the system frame structure with multiple foundations and subsoils. The influence of the three-dimensional ground excitation and the effect of the soil-structure interaction on the structural response are considered. The ground excitations are the acceleration at the Port Island of the 1995 Kobe earthquake, and at Duzce of the 1999 Turkey earthquake. The investigation shows that a simultaneous horizontal and vertical ground excitation can amplify the response of the structure, not only structures with fixed bases but also structures with subsoil compliance. Soil can reduce the forces induced in the structure. However, it can strongly amplify the induced vibrations in the structure, especially in the vertical direction.
Paper 104: [Read]
Keywords: 3D ground excitation, SSI, FEM-BEM, near-source earthquakes, secondary structures