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Showing 3 results for Seismic Behavior

M.a. Hariri Ardebili, H. Mirzabozorg, R. Kianoush,
Volume 2, Issue 4 (10-2012)
Abstract

In the present paper, nonlinear behavior of mass concrete simulated by smeared crack model is combined with Endurance Time Analysis (ETA) method for studying seismic response of arch dams. ETA is a time-history based dynamic pushover procedure in which special predesigned intensifying acceleration functions are used for analysis and estimation of structural responses in various performance levels by just a single analysis. For this purpose 203m DEZ arch dam is selected as case study and the finite element model of dam-reservoir-foundation system is excited in various performance levels. It was found that ETA provides reasonable responses in comparison with Time-History Analysis (THA) at equivalent target time. In addition, ETAleads to acceptable estimation of crack profiles within dam body and can reduce the total time of analyses, meaningfully. Generally, it was concluded that ETA can be considered as an alternative of THA in nonlinear analysis of arch dams.
M. Mohebbi, S. Moradpour , Y. Ghanbarpour,
Volume 4, Issue 1 (3-2014)
Abstract

In this research, optimal design and assessment of multiple tuned mass dampers (MTMDs) capability in mitigating the damage of nonlinear steel structures subjected to earthquake excitation has been studied. Optimal parameters of TMDs on nonlinear multi-degree-of-freedom (MDOF) structures have been determined based on minimizing the maximum relative displacement (drift) of structure where for solving the optimization problem the genetic algorithm (GA) has been used successfully. For numerical analysis, three and nine storey 2-D moment resisting nonlinear steel frames subjected to far-field and near-field earthquakes and optimal MTMDs has been designed for different values of mass ratio and TMDs number. According to the results of numerical simulations, it can be said that MTMDs mechanism could reduce the damage of nonlinear steel structures where the effectiveness increases by increasing TMDs mass ratio. Also the performance of MTMDs depends on earthquake characteristics, mass ratio and TMDs configuration where in this research the effective case has been locating TMDs on top floor in parallel configuration.
M. Yazdanian, S. Ghasemi,
Volume 7, Issue 4 (10-2017)
Abstract

Impulsive and convective frequencies are one of the most important subjects for evaluation of the seismic behavior of tanks. These two frequencies are defined by Housner and used for obtaining Rayleigh damping in time history analysis. ACI 350 and NZSEE standards have suggested some analytical solutions for finding convective and impulsive frequencies. These frequencies can also extract from modal analysis by finite element (FE) software. In current study, these frequencies are extracted by using FE software and performing modal analysis. Also these modes are compared with analytical methods from ACI and NZSEE standards. Based on the results, convective frequencies obtained from FE and ACI and NZSEE methods are so close together, with just two percent variation between FE and analytical codes, while there are significant differences among these methods for impulsive frequencies. Furthermore, this study shows that the wall thickness has no effect on the convective frequencies, while it is completely opposite for impulsive frequency. When the wall thickness rises by 1.5 times, impulsive frequencies increase by 1.75, 1.55 and 1.48 times for finite element, NZSEE and ACI methods, respectively. In addition, based on the observations, when the liquid height is low, NZSEE method presents high values of impulsive frequency.



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