Simple formulas for the estimation of maximum rotational response of one-storey asymmetric systems under seismic excitation

Abstract eng:
Structures characterized by non coincident centre of mass CM and centre of stiffness CK (Fig. 1), also referred to as asymmetric (or eccentric) structures, develop a coupled lateral-torsional response when subjected to seismic excitation. This coupled behavior may increase significantly the local peak dynamic response of such a structure, as compared to that of an equivalent system with coincident center of mass and center of stiffness (equivalent non-eccentric system). In this paper, starting from a closed-form formulation identified in previous research works by the authors, an estimation of the maximum rotational response of one-storey asymmetric systems under seismic excitation is obtained and developed with respect to different applications. In detail: (1) a corrective eccentricity for the evaluation of the dynamic response of asymmetric systems through “equivalent” static procedures is identified, (2) a sensitivity analysis is carried out upon the accidental eccentricity, (3) the increase in the peak local displacement due to the eccentricity is evaluated at the corner-point of the side of the system. The results provide useful insight into understanding the torsional behavior of asymmetric systems and may directly used for preliminary design and/or check of results obtained through three-dimensional finite-element modeling of the structural system.

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