Derivation and parametric evaluation of frequency response functions of elastic and inelastic structures under pulse-type ground excitations

Document Type : Article

Authors

1 Associate Professor, \r\nFaculty of Civil Engineering, \r\nUniversity of Tabriz

2 Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran

10.24200/j30.2024.63654.3280

Abstract

In this paper, the elastic and inelastic responses of yielding single-degree-of-freedom (SDOF) systems with bilinear hysteretic behavior subjected to pulse-type near-fault ground motions are investigated. The evaluated responses are the relative displacement and total acceleration of the structure in the form of frequency response functions. The analytical pulse model proposed by Mavroeidis and Papageorgiou, whose input parameters have clear physical meanings, is used to represent near-fault ground motions. A parametric study with six dimensionless variables is performed to evaluate the frequency response functions of SDOF structures. Out of these six variables, two variables are related to the input pulse excitation, another two variables are related to the properties of the structure, and the last two involve the ratio between the excitation and the structure; they are: the number of pulses, the pulse phase angle (shape), the damping ratio of the structure, the post-yield stiffness ratio of the structure, the excitation- (pulse-) to-structure frequency ratio, and the ratio of the excitation (pulse) amplitude to the yield strength of the structure. The obtained results reveal a notable similarity in the frequency response functions of total acceleration and relative displacement for linear elastic SDOF structures. However, the characteristics of these two responses are completely different when yielding occurs in bilinear SDOF structures. Furthermore, the effect of various parameters of the structure and the input pulse on the structural responses differs depending on the linear or nonlinear behavior of the system. For example, in a linear elastic structure, the maximum frequency responses of displacement and total acceleration always increase with increasing the number of pulses; however, in an elastic-perfectly plastic structure or in a bilinear structure with small post-yield stiffness ratio, the maximum frequency response of total acceleration remains almost constant regardless of the number of input pulses when yielding occurs. For the displacement response, the number of pulses that cause the maximum frequency response is different at different levels of nonlinear behavior.

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Sharif Journal of Civil Engineering

Articles in Press, Accepted Manuscript
Available Online from 19 March 2025

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