Document Type : Technical Note
Science and Research Branch, IAU, Tehran
International Institute of Earthquake Engineering and Seismology (IIEES)
In this research, the seismic performance capabilities of both framed and bundled tube systems are studied in order to assess the dynamic response of symbolic asymmetric mid-rise steel structures subjected to both far and near-field earthquake records. For this purpose, two 10 story structural models based on framed and bundled tube skeletons were selected and designed. The main criterion considered in selecting strong earthquake records for performing nonlinear time history analyses is the existence of high amplitude and long period coherent pulse or multiple pulse features in the ground velocity time history. The mentioned powerful velocity pulse makes more seismic demands and would cause a complicated 3D dynamic response which conveys the maximum seismic drift demand from lower stories to middle or even upper ones. Yet, the participation of higher vibration modes in seismic behavior of the studied structures were also taken into account. Overall, seismic response parameters of asymmetric rigid framed tube and bundled tube skeletons are not effectively sensitive to small amounts of mass eccentricity. Moreover, this research analytical assessments show larger amplitude for the seismic nonlinearity of plastic hinges in flexible edges of the structure plan compared to stiff edges. Additionally, the floors dynamic torsional movements cause unequal yielding mechanisms, which are formed in the sided bending frames. Moreover, during the aforementioned process, the frames located at one side of the plan would reach to collapse prevention performance level (CP). Finally, it is observed that rigid framed tubes and bundled tubes can satisfy the Iranian design code restrictions for story drift.