Approximating earthquake records by stationary wavelet transform (SWT), is major work in this thesis. Approximation was done by a proposed technique which is based on selecting wavelet coefficients regard to their energy and dynamic property of structure. The main property of this new method is the huge similarity of some structural responses to original and approximated records when the time representation of these two types of records are very different. In this way, Eighteen approximated records was generated for a structure and one original record by eighteen approximation patterns. We also investigated the influence of earthquake record time representation on structural responses. Actually we choose one of these records which has minimum correlation with original record and high similarity of structural response to original and this approximated record (bigger than a threshold). By changing dynamic property of structures, their effect on dependency of response to record shape was studied. We also studied the influence of arias intensity and peak ground acceleration on dependency of responses to time representation of earthquake records. In this thesis, 45600 linear and nonlinear analysis were done for three original record, Eighteen approximated records, 400 structure with 40 different periods and 10 combination of dynamic property. The main results of this study are that earthquake time representation, peak ground acceleration and arias intensity has minor (no) effect on seismic behavior of single degree of freedom structures. Effect of dynamic property of structures on dependency of response to record shape are vary by record and structural period. It is shown that post to pre yield stiffness ratio has no effect on structural response dependency to record shape.
