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Structural Engineering and Mechanics
  Volume 71, Number 4, August25 2019, pages 445-458
DOI: http://dx.doi.org/10.12989/sem.2019.71.4.445
 


Dynamic identification of soil-structure system designed by direct displacement-based method for different site conditions
Vahidreza Mahmoudabadi, Omid Bahar, Mohammad Kazem Jafari and Amir Safiey

 
Abstract
    This study mainly aims to assess the performance of soil-structure systems designed by direct displacement-based method coupled with strong column-weak beam design concept through various system identification techniques under strong ground motions. To this end, various system identification methods are employed to evaluate the dynamic characteristics of a structure (i.e., modal frequency, system damping, mode shapes, and plastic hinge formation pattern) under a strong seismic excitation considering soil-structure interaction for different site conditions as specified by ASCE 7-10. The scope of the study narrowed down to the code-complying low- to high-rise steel moment resisting frames with various heights (4, 8, 12, 16-story). The comparison of the result of soil-structure systems with fix-based support condition indicates that the modal frequencies of these systems are highly influenced by the structure heights, specifically for the softer soils. This trend is more significant for higher modes of the system which can considerably dominate the response of structures in which the higher modes have more contribution in dynamic response. Amongst all studied modes of the vibration, the damping ratio estimated for the first mode is relatively the closet to the initial assumed damping ratios. Moreover, it was found that fewer plastic hinges are developed in the structure of soil-structure systems with a softer soil which contradicts the general expectation of higher damageability of such structural systems.
 
Key Words
    direct displacement design; dynamic structural identification; soil-structure system; steel moment resisting structures
 
Address
Vahidreza Mahmoudabadi: Glenn Department of Civil Engineering, Clemson University, Clemson SC 29634, USA
Omid Bahar: International Institute of Earthquake Engineering and Seismology (IEES), Tehran, Iran
Mohammad Kazem Jafari: International Institute of Earthquake Engineering and Seismology (IEES), Tehran, Iran
Amir Safiey: Glenn Department of Civil Engineering, Clemson University, Clemson SC 29634, USA
 

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