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The objective of this research is to evaluate the effects of soil‐structure interaction (SSI) on the modal characteristics and on the dynamic response of structures. The stress had an impact on the overall behaviour of five storeys reinforced concrete (R/C) buildings typically encountered in Algeria. Sensitivity studies are undertaken in order to study the effects of frequency content of the input motion, frequency of the soil structure system, rigidity and depth of the soil layer on the dynamic response of such structures. This investigation indicated that the rigidity of the soil layer is the predominant factor in soil‐structures interaction and its increases would definitely reduce the deformation of the R/C structures. On the other hand, increasing the period of the underlying soil will cause an increase in the lateral displacements at storey levels and create irregularity in the distribution of storey shears. Possible resonance between the frequency content of the input motion and soil could also play an important role in increasing the structural response.

We present in this research article, the improvements that we made to create a four nodes flat quadrilateral shell element for geometrically nonlinear analysis, based on corotational updated lagrangian formulation. These improvements are initially related to the improvement of the in-plane behaviour by incorporation of the in-plane rotational degrees of freedom known as “drilling degrees of freedom” in the membrane displacements field formulation. In the second phase, a co-rotational spatial local system of axes which adapts well to the problems of quadrilateral elements is adopted, while ensuring simplicity and effectiveness at numerical level. The required goal being mainly to have a robust thin shell element associated with a simplified formulation. The obtained element remains economic, and showing a robust behaviour in delicate situations of tests.

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Nowadays, the new and emerging concept of seismic structural design, the so-called performance-based design, requires careful consideration of all aspects involved in structural analysis. One of the most important aspects of structural analysis is soil-structure interaction (SSI). Such interaction may alter the dynamic characteristics of structures and consequently may be beneficial or detrimental to the performance of structures. In order to observe such effects we study the seismic response of an idealized small city composed of five equally spaced, five storey reinforced concrete buildings anchored in a soft soil layer overlaid by a rock half-space. Our results show predict response amplification of the buildings in the near field in accordance with the results observed in similar cases.