Assessment of Design Recommendations for Torsionally Unbalanced Multistory Buildings

Multistory models are studied to assess design recommendations for torsionally unbalanced multistory buildings. Structural systems are assumed as shear beams with nonlinear lateral-resisting elements oriented along two orthogonal directions and subjected to a bidirectional earthquake ground motion. Five-story rigid-diaphragm models with mass or stiffness eccentricity are considered in the study. Accidental eccentricity is not included in the modeling and, therefore, its related recommendations are not assessed. Design recommendations studied here are based on the simple static procedure and include two values and an expression for the amplification factor α to compute story eccentricities, three values of the torsion-shear reduction factor δ, an additional lateral force Ft to be applied at the building top level, and a minimal story eccentricity for the building. Design recommendations to control ductility demands of torsionally unbalanced multistory buildings are given.

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

[2]  A. M. Chandler,et al.  Effect of transverse load-resisting elements on inelastic earthquake response of eccentric-plan buildings , 1994 .

[3]  R. Go´mez,et al.  The Mexico Earthquake of September 19, 1985—Complementary Technical Norms for Earthquake Resistant Design, 1987 Edition , 1988 .

[4]  J. L. Humar,et al.  Effect of orthogonal inplane structural elements on inelastic torsional response , 1999 .

[5]  Anil K. Chopra,et al.  Dynamics of Structures: Theory and Applications to Earthquake Engineering , 1995 .

[6]  W. K. Tso,et al.  Evaluation of Seismic Torsional Provisions in Uniform Building Code , 1995 .

[7]  W. K. Tso,et al.  An evaluation of the New Zealand code torsional provision , 1993 .

[8]  A. M. Chandler,et al.  A modified static procedure for the design of torsionally unbalanced multistorey frame buildings , 1993 .

[9]  Juan Carlos de la Llera,et al.  Torsion in Earthquake Response and Design of Buildings , 1997 .

[10]  W. K. Tso,et al.  STATIC ECCENTRICITY CONCEPT FOR TORSIONAL MOMENT ESTIMATIONS , 1990 .

[11]  Arturo Tena-Colunga,et al.  International Seismic Zone Tabulation Proposed by the 1997 UBC Code: Observations for Mexico , 1999 .

[12]  W. J. Hall,et al.  Dynamics of Structures—Theory and Applications to Earthquake Engineering , 1996 .

[13]  Larry. Korba.  National Research Council of Canada , 1948, Nature.

[14]  A. M. Chandler,et al.  Seismic torsional response and design procedures for a class of setback frame buildings , 1995 .

[15]  A. M. Chandler,et al.  Inelastic seismic response of code‐designed multistorey frame buildings with regular asymmetry , 1993 .

[16]  T. Paulay.  A review of code provisions for torsional seismic effects in buildings , 1997 .