Parametric study of the non-linear seismic response of three-dimensional building models

The behavior of buildings when subjected to severe seismic events, that force them to enter in the non-linear range is studied. Using simple three-dimensional models of structures, the influence that several parameters have on the seismic response can be evaluated, namely: The number of resistant planes parallel to the earthquake action, the degree of torsional coupling (Ω_θ the uncoupled fundamental vibration period (T_Y1), the normalized static eccentricity (e/r), the uncoupled lateral frequencies ratio (ω_X1/ω_Y1), the torsional stiffnesses ratio (γX), and the overall ductility of design (μ). Two hoizontal components of four acceleraion records of the ground moion recorded during the earthquake of 3 March 1985 in the central zone of Chile were used as seismic excitation. The records were normalized to have the Peak Ground Acceleration (PGA) equal to 0.4g. The non-linear dynamic analysis was carried out using the time history response (THR) method and subjecting each structural model to a ground motion repesented by each of the eight normalized seismic records, through which we obtained eight value for each relevant response. Due to the fact that the non-linear behavior of the structure is sensitive to the particularities of the seismic excitation, it is considered advisable to average the responses over the set of seismic records used. Finally, the main conclusion ontained were: (i) the displacements at each floor level do not vary with the number of resistant planes parallel to the direction of seismic action in structure with moderate static eccentricity (e/r ≤ 0.50) and low oveall ductility of design (μ ≤ 4), which is the opposite effect as that observed for the displacements and ductilities of each frame; (ii) the relevant parameters in this type of study are identified.