چكيده فارسي :
The consequences of near-fault earthquakes including translational and rotational accelerograms are investigated in this study. In some cases, relatively significant rotational excitations are induced to the structure during the ground intensive shaking. A three-dimensional 40-story steel moment frame structure is utilized in this paper in order to evaluate the effects of near-fault ground motions including rotational components. A number of scaled earthquake records which contain forward, backward and neutral directivity effects are enforced to the mentioned structural model. Presence of energized coherent velocity pulses as well as high amplitude acceleration spikes in the time history of earthquake records were the major criterion for selecting the ensemble of ground motions. The results obtained by numerical nonlinear time history analyses subjected to six components of each earthquake record are compared to those captured by analyses including only three transitive components. The seismic response parameters of the studied model are intensively influenced by those strong earthquake records which contain powerful forward directivity effects. The computational results indicate that tall buildings with the moment resisting frame system possesses substantial reserve strength exposed to the most of the selected records while it would not be able to satisfy the seismic design requirements under rotational components of the Bam record. Keywords: seismic design, near-fault record, rotational components, steel rigid frame structure Seismic ground movements at a point on the surface can be disintegrated to six components, namely three transitive components and three rotational components; translational components include two components in the horizontal plane, and one in the vertical direction. Rotation about horizontal axes results in rising of rocking, whereas the rotational component about a vertical axis is able to produce serious effects even in symmetrical buildings. Due to remarkable effects of earthquake records on the overall response parameters of structures, rotational components of strong ground motions are recently of notable issues for widespread researches by engineering and research communities. In this study, performance capabilities of moment resisting frame system is investigated in order to specify the seismic response parameters of steel tall resistant structures exposed to strong near-field earthquakes including three transitive and three rotational components. A 40-story MRF structural model is selected and designed according to the Iranian seismic code 2800 (fourth edition) and Iranian National Building Code (Steel Structures ndash; Division 10). The plan of the studied model is displayed in Figure1. The seismic demand parameters have been evaluated by applying a number of non-linear dynamic time history analyses. The seismic responses in terms of peak interstory drift, residual interstory drift, base shear and configuration of plastic hinges are expressed and compared for a model subjected to three components with the same model subjected to the six components of earthquake records. Moreover, the magnitude of some internal-forces time histories of a selected critical column is demonstrated and described. This issues are done in order to observe, remark and compare the effect of rotational components on the tall steel rigid frame located on the site of soil type II. nbsp;
