Issue 47

V. Alecci et alii, Frattura ed Integrità Strutturale, 47 (2019) 161-167; DOI: 10.3221/IGF-ESIS.47.13 167 torsional amplifications of lateral displacements. The elastic amplifications of lateral displacements obtained by modal analysis are conservative with respect to the inelastic ones. Tests on case study buildings gave promising results [19-20]. The assumption of the conservativeness of the elastic envelope appears to be valid for torsionally flexible and moderately torsionally stiff (framed) building structures. On the contrary, it does not hold true for very torsionally stiff structures, such as shear-walled buildings [21]. Another method, proposed by Ghersi et al., [22], is based on modal analysis involving the definition of corrective eccentricities used to determine the application points of the load vectors, on either sides of the CM so as to obtain an envelope of plan distribution of maximum displacements. Corrective eccentricities have been calibrated from response of a one-storey building while their application to multistory buildings requires complex parameters definition. F INAL CONSIDERATIONS rchitectural design in seismic areas is the first and fundamental step to guarantee good seismic performance. Architectural designer must be aware that his choices of building morphology, plan and vertical layout of resisting structures, member tentative dimensions, have a profound impact on the behavior under seismic actions. This paper has focused on the effects of irregularity conditions resulting from architectural design. It is demonstrated that irregularities, arising from economical, functional and aesthetical/formal requirements, cannot be prohibited; however, architectural designer must know irregularity conditions, their outcome on seismic response and how to mitigate their effects. A CKNOWLEDGEMENTS he financial support of ReLUIS through the Progetto Esecutivo Convenzione DPC/ReLUIS 2017 – PR2 Strutture in cemento armato – is gratefully acknowledged. R EFERENCES [1] De Stefano, M. and Pintucchi, B. (2008). A review of research on seismic behavior of irregular building structures since 2002, Bulletin of earthquake Engineering, 6(2), pp. 285-308. [2] Rosenlueth, E. and Meli, R. (1986). The 1985 Earthquake: Causes and effects in Mexico City, Concrete International, 8(5), pp. 23–34. [3] Tso, W. K. (1990). Static Eccentricity Concept for Torsional Moment Estimations, Journal of Structural Engineering, 116(5) pp. 1199–1212. [4] Chopra, A. K. and Goel, R. K. (1991). Evaluation of torsional provisions in seismic codes, Journal of Structural Engineering, 117(12), pp. 3762–3782. [5] De Stefano, M. Faella, G. and Ramasco, R. (1993). Inelastic response and design criteria of plan-wise asymmetric systems, Earthquake Engineering and Structural Dynamics, 22(3), pp. 245-259. [6] Chandler, A. Correnza, J. C. and Huchinson, G. L. (1995). Influence of accidental eccentricity on inelastic seismic torsional effects in buildings, Engineering Structures, 17(3), pp. 167-178. [7] De Stefano, M. and Rutenberg, A. (1997). A comparison of the present SEAOC/UBC torsional provisions with the old ones, Engineering Structures, 19(8), pp. 655-664. [8] Foraboschi, P. (2016). The central role played by structural design in enabling the construction of buildings that advanced and revolutionized architecture. Construction and Building Materials, 114, pp. 956-976. [9] Foraboschi, P. (2016). Versatility of steel in correcting construction deficiencies and in seismic retrofitting of RC buildings. Journal of Building Engineering, 8, pp. 107-122. [10] Foraboschi, P. 2016. Structural layout that takes full advantage of the capabilities and opportunities afforded by two- way RC floors, coupled with the selection of the best technique, to avoid serviceability failures. Engineering Failure Analysis, 70, pp. 387-418. [11] Sassu, M. Puppio, M. L. Mannari, E. (2017). Seismic Reinforcement of a R.C. School Structure with Strength Irregularities throughout External Bracing Walls, Buildings, 7(58). DOI:10.3390/buildings7030058. MDPI. A T