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Showing 3 results for Near-Field Earthquake

A. H. Molavi-Tabrizi, F. Khoshnoudian,
Volume 10, Issue 3 (9-2012)

The application of fuzzy algorithms in the response control of a base isolated building with MR dampers is investigated in this

paper. Most of the previous researches in this field have been focused on fuzzy algorithms with linear membership function

however in the current study the membership functions are assumed to be Gaussian and their effectiveness is studied. For this

purpose, an eight-story building with regularity in plan and height is considered. The adopted base isolation system includes

linear bearings and control devices for improving the behavior of isolated structure under near field ground motions. MR

dampers are used to reduce base displacements and have the capacity of 1000 kN with the maximum applied voltage of 10 V. In

order to verify the control procedure and analyzing the structure, a simulation procedure is developed. This procedure performs

linear analysis of the structure in presence or in absence of the base isolation system. Moreover, the simulation procedure is able

to appropriately determine the MR damper voltage using fuzzy logic algorithms and then analyzing the whole system too. Finally,

seven near-field earthquake records are chosen in order to study the structure responses under these records and the obtained

results demonstrate the accuracy of proposed control procedure

M. Davoodi, M. Sadjadi,
Volume 13, Issue 3 (12-2015)

The distinctive characteristics of near-field earthquake records can lead to different structural responses from those experienced in far-field ones. Furthermore, soil-structure interaction (SSI) can have a crucial influence on the seismic response of structures founded on soft soils however, in most of the time has been neglected nonchalantly. This paper addresses the effects of near-field versus far-field earthquakes on the seismic response of single degree of freedom (SDOF) system with considering SSI. A total 71 records were selected in which near-field ground motions have been classified into two categories: first, records with a strong velocity pulse, (i.e. forward-directivity) second, records with a residual ground displacement (i.e. fling-step). Findings from the study reveal that pulse-type near-field records generally produce greater seismic responses than far-field motions especially at high structure-to-soil stiffness ratios. Moreover, the importance of considering SSI effects in design of structures is investigated through an example. Finally, parametric study between Peak Ground Velocity to Peak Ground Acceleration ratio (PGV/PGA) of pulse-like ground motions and maximum relative displacement indicate that with increase in structure-to-soil stiffness ratios, earthquakes with higher PGV/PGA ratio produce greater responses.

Hamed Tajammolian, Faramarz Khoshnoudian, Nasim Partovi Mehr,
Volume 14, Issue 8 (12-2016)

This study is devoted to investigate the effects of mass eccentricity in seismic responses of base-isolated structures subjected to near field ground motions. Superstructures with 3, 6 and 9 stories and aspect ratios equal to 1, 2 and 3 have been idealized as steel special moment frames resting on a reasonable variety of Triple Concave Friction Pendulum (TCFP) bearings considering different period and damping ratios for the isolators. Three-dimensional linear superstructure mounted on nonlinear isolators are subjected to 3 components of near-field ground motions. Under 25 near-field ground motions, effects of mass eccentricity on the main system parameters are studied. These parameters are selected as the main engineering demands including maximum isolator displacement and base shear as well as peak superstructure acceleration. The results indicate that the mass eccentricities has not a remarkable effect on isolator displacement. In contrary to displacement, torsional effect of mass eccentricity raise the base shear up to 1.75 times in a three-story superstructure. Additionally, mass eccentricity can amplify the roof acceleration of a nine-story model approximately 3 times in comparison with a symmetric superstructure. It is also concluded that eccentricity in the direction of the subjected earthquake has the most impact on base shear while the isolator displacement and roof acceleration has mostly influenced by the eccentricity perpendicular to the earthquake path.

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