<sod>Propagation of [[seismic waves]] due to strong ground motions creates three [[translational]] (two horizontal and one vertical) and three [[rotational]] (two rocking and one torsional) components on the ground surface. To study the nature of [[earthquakes]], seismologists and earthquake engineers deploy [[accelerometers]] and [[seismometers]] on the ground surface and near [[active faults]] in order to record the translational ground motions after the occurrence of an earthquake. The rotational components are, then, estimated in terms of the gradient of the recorded translational ground motions.<ref>M. R. Falamarz-Sheikhabadi, M. Ghafory-Ashtiany, Approximate formulas for rotational effects in earthquake engineering, Journal of Seismology, Vol.16 (2012) 815-827.</ref> In current [[seismic code]]s, the effect of the rotational components of strong ground motions is partially considered in the design of resistant structures against earthquakes. However, recent seismological data indicated that the ratio of the amplitude of the rotational components to the translational components in the [[near field]] can be significantly larger than that was expected.<ref>M. D. Trifunac, The role of strong motion rotations in the response of structures near earthquake faults, Soil Dynamics and Earthquake Engineering, Vol.29 (2009) 382-393.</ref> In the past decade, this observation leaded to the attraction of the theoretical studies toward the near-field effects of the [[earthquake rotational loading]] on the structural response.<ref> M. R. Falamarz-Sheikhabadi, M. Ghafory-Ashtiany, Rotational components in structural loading, Soil Dynamics and Earthquake Engineering, Vol. 75 (2015) 220-233.</ref> The results of these studies implied that the rotational components may result in significant damage of structures sensitive to high-frequency excitations, their effect should be fully incorporated in seismic codes.<ref>M. R. Falamarz-Sheikhabadi, Simplified relations for the application of rotational components to seismic design codes, Engineering Structures, Vol.59 (2014) 141-152.</ref><eod>
<sod>Propagation of [[seismic waves]] due to strong ground motions creates three [[translational]] (two horizontal and one vertical) and three [[rotational]] (two rocking and one torsional) components on the ground surface. To study the nature of [[earthquakes]], seismologists and earthquake engineers deploy [[accelerometers]] and [[seismometers]] on the ground surface and near [[active faults]] in order to record the translational ground motions after the occurrence of an earthquake. The rotational components are, then, estimated in terms of the gradient of the recorded translational ground motions.<ref>M. R. Falamarz-Sheikhabadi, M. Ghafory-Ashtiany, Approximate formulas for rotational effects in earthquake engineering, Journal of Seismology, Vol.16 (2012) 815-827.</ref> In current [[seismic code]]s, the effect of the rotational components of strong ground motions is partially considered in the design of resistant structures against earthquakes. However, recent seismological data indicated that the ratio of the amplitude of the rotational components to the translational components in the [[near field]] can be significantly larger than that was expected.<ref>M. D. Trifunac, The role of strong motion rotations in the response of structures near earthquake faults, Soil Dynamics and Earthquake Engineering, Vol.29 (2009) 382-393.</ref> In the past decade, this observation leaded to the attraction of the theoretical studies toward the near-field effects of the [[earthquake rotational loading]] on the structural response.<ref> M. R. Falamarz-Sheikhabadi, M. Ghafory-Ashtiany, Rotational components in structural loading, Soil Dynamics and Earthquake Engineering, Vol. 75 (2015) 220-233.</ref> The results of these studies implied that the rotational components may result in significant damage of structures sensitive to high-frequency excitations, and, hence, their effect should be incorporated in seismic codes.<ref>M. R. Falamarz-Sheikhabadi, Simplified relations for the application of rotational components to seismic design codes, Engineering Structures, Vol.59 (2014) 141-152.</ref><eod>