Effects of Soil-Structure Interaction on the Seismic Response of Existing R.C. Frame Buildings

Student: M. Jawad Arefi
Supervisors: Assoc. Prof. Misko Cubrinovski, Dr. Stefano Pampanin

ABSTRACT

Comprehensive experimental and analytical studies have been carried out to understand the behaviour of existing frame buildings constructed before the introduction of seismic design codes in 1970’s. Different aspects of the response have been investigated and inherent weaknesses have been pointed out.
This usually has been done assuming a fixed-base structure while ignoring the flexibility of soil and foundation.
In this thesis, the interaction between the super-structure and sub-structure (SSI) is investigated by modelling the soil as simple as possible to capture the overall response of the system.
As new analytical hysteresis rules and more advanced tools of analysis have been developed in recent years, first the nonlinear response of a single-degree-of-freedom (SDOF) system which can be representative of a broad range of existing or newly designed structures, is investigated while allowing for flexibility of the soil-foundation system and SSI effects.
This simple soil model then is employed to existing nonlinear frame models to quantify the effect of SSI on the overall response of actual structures. The use of flexible base in the analysis can lead to reduction in the structural response and damage consequences in joints and infills.
In a further step, the assessed existing frames are retrofitted in beam-column joints area and the effects of flexible base condition on structural demand are examined in more detail.
The results of this study suggest that the compliance of simply modelled soilfor typical building structures have in average beneficial effects in terms of structural demand especially for stiff structures. On the other hand, the governing component of these effects, i.e. rocking of foundation, can result in average to higher absolute deformation of floors which points out to potential pounding problems for structures existing in close vicinity to each other.

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