The effect of the vertical excitation on horizontal response of structures Hosein Ghaffarzadeh and Ali Nazeri Department of Civil Engineering, University of Tabriz, Tabriz, Iran (Received February 8, 2014, Revised April 21, 2015, Accepted April 27, 2015) Abstract. It is usual in design and assessment of structures to isolate the effects of vertical and horizontal excitations by ignoring their coupling effects. In this situation, total structural response is obtained by employing the well-known combination rules whereby independent assumed response components of earthquakes are combined. In fact, the effects of the simultaneity of the ground motion components are ignored. In this paper, the effect of vertical excitation on horizontal response of structures, the coupling of vertical and horizontal responses, has been evaluated. A computer program is prepared to perform nonlinear dynamic analysis based on the derived governing equations of coupled motions. In the case of simultaneous excitation the results show significant increases in spectral displacement in some periods of vibration in comparison to only horizontally excited systems. Moreover, whenever ratio of the vertical peak ground acceleration to horizontal one become larger, the significant increase in horizontal spectral displacements are observed. Keywords: simultaneous excitation; coupled horizontal and vertical components; vertical earthquake
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