Natural and accidental torsion in one‐storey structures on elastic foundation under non‐vertically incident SH‐waves

Factors α and β used in equivalent static analysis to account for natural and accidental torsion are evaluated with consideration of soil–structure interaction. The combined torsional effects of structural asymmetry and foundation rotation are examined with reference to a single monosymmetric structure placed on a rigid foundation that is embedded into an elastic half-space, under to the action of non-vertically incident SH waves. Dynamic and accidental eccentricities are developed such that when used together with the code-specified base shear, the resulting static displacement at the flexible edge of the building is identical to that computed from dynamic analysis. It is shown that these eccentricities do not have a unique definition because they depend on both the selection of the design base shear and the criterion used for separation of the torsional effects of foundation rotation from those of structural asymmetry. Selected numerical results are presented in terms of dimensionless parameters for their general application, using a set of appropriate earthquake motions for ensuring generality of conclusions. The practical significance of this information for code-designed buildings is elucidated. Copyright © 2006 John Wiley & Sons, Ltd.

[1]  J. E. Luco.  Torsional response of structures to obliquely incident seismic sh waves , 1976 .

[2]  J. Luco,et al.  Response of circular foundation to spatially random ground motion , 1987 .

[3]  George Gazetas,et al.  Analysis of machine foundation vibrations: state of the art , 1983 .

[4]  Juan Carlos de la Llera,et al.  Evaluation of Code Accidental‐Torsion Provisions from Building Records , 1994 .

[5]  H. L. Wong,et al.  Response of a rigid foundation to a spatially random ground motion , 1986 .

[6]  Luis Eduardo Pérez-Rocha,et al.  Effects of foundation embedment during building–soil interaction , 1998 .

[7]  Anestis S. Veletsos,et al.  Seismic Interaction of Structures and Soils: Stochastic Approach , 1989 .

[8]  W. K. Tso,et al.  Seismic torsional provisions for dynamic eccentricity , 1980 .

[9]  Juan Carlos de la Llera,et al.  Accidental torsion in buildings due to base rotational excitation , 1994 .

[10]  Akira Mita,et al.  IMPEDANCE FUNCTIONS AND INPUT MOTIONS FOR EMBEDDED SQUARE FOUNDATIONS , 1989 .

[11]  H. L. Wong,et al.  Seismic response of foundations embedded in a layered half‐space , 1987 .

[12]  A. M. Chandler,et al.  Code design provisions for torsionally coupled buildings on elastic foundation , 1987 .

[13]  Anil K. Chopra,et al.  Elastic Earthquake Analysis of a Class of Torsionally Coupled Buildings , 1977 .

[14]  W. K. Tso,et al.  An alternative path to seismic torsional provisions , 1982 .

[15]  A. M. Chandler,et al.  Evaluation of code torsional provisions by a time history approach , 1987 .

[16]  Keiiti Aki,et al.  Strain, tilt, and rotation associated with strong ground motion in the vicinity of earthquake faults , 1982 .

[17]  J. E. Luco,et al.  Local characterization of free-field ground motion and effects of wave passage , 1980 .

[18]  R. Dobry,et al.  Apparent propagation velocity of body waves , 1982 .

[19]  Akira Mita,et al.  Response of a circular foundation on a uniform half-space to elastic waves , 1987 .

[20]  G. Hahn,et al.  Torsional Response of Unsymmetric Buildings to Incoherent Ground Motions , 1994 .

[21]  Bruce A. Bolt,et al.  Earthquake strong motions recorded by a large near‐source array of digital seismographs , 1982 .

[22]  Javier Avilés,et al.  RESPUESTA ACOPLADA DE TRASLACIÓN Y TORSIÓN DE ESTRUCTURAS ASIMÉTRICAS INCLUYENDO LA INTERACCIÓN CON EL SUELO , 2002 .

[23]  J. E. Luco.  Torsional response of structures for SH waves: The case of hemispherical foundations , 1976 .

[24]  Michio Iguchi,et al.  AN APPROXIMATE ANALYSIS OF INPUT MOTIONS FOR RIGID EMBEDDED FOUNDATIONS , 1982 .

[25]  Yu Tang,et al.  Deterministic Assessment of Effects of Ground‐Motion Incoherence , 1990 .