Dynamic analysis of steel chimney considering rotational components of earthquake

The present study deals with dynamic analysis of steel chimney taking rotational components of earthquake into account. The translational components of the earthquake have been used in order to obtain the rotational components of the earthquake, based on the intersecting isotropic elastic wave propagation. For this purpose, a transitional component of ground motion using frequency discrete Fourier transformed to discrete frequency and G value for each frequency determined. Then, the incident angle of the wave was calculated for each frequency then, fourier spectrums of rocking and torsion components of ground motion were calculated. Finally, the inverse of Fourier conversion were calculated to evaluate time history of rocking and torsion components of ground motion .In order to verify the proposed methodology, the rotational components of San Fernando Earthquake were determined based on the proposed model and compared to Li and Liang's results. In Li's model, the incident angle and apparent wave velocity was supposed to be constant while in the present study the incident angle and apparent wave velocity were variable based on each frequency Then, the rotational components of San Fernando, Tabas and Taft were calculated based on the proposed model and the results were used in dynamic analysis of the steel chimneys. Finally, dynamic analyses of three model of steel chimney are presented to evaluate the effects of combined translational and rotational components on the seismic response of the chimney. The deduced results show that the maximum values of displacement, stresses and shear force and also, the distribution of them have changed significantly. On the other hand, the magnitudes of these responses for different earthquakes with respect to the frequency content of rotational components of the earthquake are different. The results indicate that the effects of earthquake rotational components on the dynamic response of steel chimneys are very significant.