Seismic response for torsionally flexible buildings : contribution to the development of the 2nd generation of Eurocode 8

The main objective of this thesis is to bring a consistent work to help the development of the second generation of Eurocode 8 for the elements related to the response of torsionally flexible buildings. The focus is put on one-storey buildings to clarify all the physical concepts and assess the procedures with simple cases. This work involved the analysis of the elastic modal properties and response of typical RC buildings, namely in what respects to its torsional modes of vibration. To achieve the objective, first, a literature review is presented to clarify the physical concepts related to torsion. It has been shown that theoretically, for the classification of torsionally flexible buildings, the torsional radius should be computed with respect to the centre of mass. Then, using results coming from analyse of numerical models, an assessment of the two new proposed procedures coming from the second generation of Eurocode 8 (for the computation of the position of the centre of stiffness and for the value of the torsional radius) has been made to clarify their use. Clearly, one procedure is more conservative by neglecting the effects of the horizontal structural elements. Using again the results coming from the numerical models, the assessment of the two conditions for the classification of buildings as torsionally flexible is presented. A consistency between those conditions could have been observed. Those results and discussions bring clarification for the new procedures of the second generation of Eurocode 8. But to be complete, the analyses should be extended to multi-storey buildings to know if the same conclusions can be drawn.