טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKhoury Waseem
SubjectSeismic Response of Perimeter Steel Frames Structures:
Asymmetric and Setback Buildings
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Robert Levy
Professor Emeritus Avigdor Rutenberg


Abstract

This is a study on the seismic response of irregular structures: Nine-story asymmetric and setback buildings were analyzed. The seismic response was studied through both global response: displacements, twist, interstory drifts; and local response: rotational ductility, plastic rotation of the elements. Many effects were considered in developing the computerized mathematical model:  shear deformation, P-delta, unidirectional vs bi-directional loading components, and bi-axial bending and axial force interaction in column modeling. The basic model for the asymmetric structures is the nine-story with one-story basement SAC project phase II structure. Peripheral SMRFs were chosen as the resisting system to seismic load. The basic model of the setback building was the same nine-story structure, but designed for a setback to 60% of the building plan at four different levels. The seismic loadings on the asymmetric and setback buildings were 10 bi-directional high-intensity historical ground motions. The nine-story asymmetric structures were analyzed with earthquake ground motions with a 2% probability of exceedence in 50 years in the Los Angles area, (2/50), and the setback structure with earthquake ground motions with 10% probability of exceedence in 50 years in the Los Angles area, (10/50). The computer program chosen for the nonlinear dynamic analysis was CANNY 1999.

The analysis for the asymmetric structures showed that peripheral SMRFs are quite effective and recommended systems that restrain responses  such as twist angles and displacements induced by twist. It was shown that setbacks caused an increased eccentricity and torsion unbalancing between the upper and lower parts of the structure, and hence led to peak results at the upper stories than at the setback level.