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An Investigation of Efficiency and Accuracy of Energy-Based Capacity Spectrum in Estimating the Seismic Demands of Buildings Original Article, C40 Vakili H, Shakeri K, Seyyedi Viand S.M, Azadi Hir M. Journal. Civil Eng. Urban. 3(5):251-259. 2013 ABSTRACT:In the conventional methods of pushover analysis, the capacity spectrum is obtained with linking roof displacement to base shear, while this relationship only is meaningful in pushover analysis with load pattern that is proportional to the first mode. In the higher modes, changes of the roof displacement is not proportional to the changes of other stories displacement, and even in some cases roof displacement is decreased with increasing base shear and reverses. Therefore, using the roof displacement for establishing the capacity spectrum in the higher modes is faced with ambiguities. Using the energy method for establishing the capacity spectrum of structure is one of the proposed methods to eliminate these ambiguities. In this method, not only the amount of the roof displacement, but also the amount and the sign of other stories displacements participate in the establishment of capacity spectrum of structure. In this research, the accuracy and efficiency of energy-based capacity spectrum has been studied on two steel moment-frame buildings under different earthquakes for using in different pushover analysis with various load patterns. The results show that using the energy method for establishing the capacity spectrum not only eliminate the existent ambiguities and problems in establishment of capacity spectrum, but also the responses of the different nonlinear static analysis by using the energy-based capacity spectrum instead of the conventional capacity spectrum (based on roof displacement) have better accuracy and efficiency. Keywords: Seismic Demands, Modal Pushover Analysis, Higher Modes, Capacity Spectrum, Energy Method منبع: [Hidden Content] دانلود: [Hidden Content].,40-251-259.pdf J. Civil Eng. Urban.,40-251-259.pdf

An Assessment of a Modal Pushover Method Based On 2DOF Modal System for Tall Asymmetric-Plan Buildings Original Article, C35 Seyyedi Viand S.M, Shakeri K, Vakili H, Azadi Hir M. Journal. Civil Eng. Urban. 3(4):216-220. 2013 ABSTRACT:Recently, a novel two-degrees-of-freedom (2DOF) modal system has been proposed by Lin and Tsai which considers bifurcating and interaction between modal translation and modal rotation. Also, they claim that the proposed system is accurate than the conventional single-degree-of-freedom (SDOF) modal system in estimating the seismic demands of asymmetric-plan buildings. In this paper, the efficiency of application of the proposed system for tall buildings is evaluated. Hence, a modal pushover analysis is performed for a sample tall asymmetric-plan building based on SDOF and 2DOF modal systems. Then, the seismic responses of building are estimated by utilizing nonlinear time history analysis (NTHA). Finally, the analytical results are compared. Results show that the efficiency of 2DOF modal system becomes considerable at high levels of building, in particular for rotational responses. Consequently, the new system may be an alternative to the SDOF modal system in estimating the seismic responses of asymmetric-plan buildings. Keywords: Asymmetric-Plan Buildings, Two-Degrees-Of-Freedom Modal Systems, Modal Pushover Analysis منبع: [Hidden Content] دانلود: [Hidden Content].,35-216-220.pdf J. Civil Eng. Urban.,35-216-220.pdf