Showing 3 results for Fahimi Farzam
M. Shahrouzi, M. Fahimi Farzam, J. Gholizadeh,
Volume 15, Issue 2 (4-2025)
Abstract
The tuned mass damper inerter systems have recently received considerable attention in the field of structural control. The present work offers a practical configuration of such a device, called double tuned mass damper inerter (DTMDI) that connects the inerter into the damper masses rather than be attached to the main structure. Soil-structure interaction is also taken into account for the soft and dense soils as well as for the fixed based condition. The H∞ norm of the transfer functions for the roof response is minimized as the objective function. The parameters of DTMDI are optimized using opposition-switching search as an efficient parameter-less algorithm in comparison with lightning attachment procedure optimization, sine cosine algorithm and particle swarm optimization. The system performance is evaluated in the frequency domain, as well as in the time domain under various earthquakes including far-field records, near-field records with forward directivity and with fling-step. The results show superiority of opposition-switching search for optimal design of the proposed DTMDI so that it can significantly reduce both the roof displacement and acceleration response for all the SSI conditions.
M. Fahimi Farzam, M. Salehi,
Volume 15, Issue 4 (11-2025)
Abstract
Reducing the degrees of freedom of building models significantly reduces computational costs in time-consuming structural engineering problems, such as dynamic analysis, nonlinear analysis, or the optimal design of structural systems. In this study, the Finite Element (FE) model of a 20-story benchmark steel building with numerous degrees of freedom (DoF) is simplified to a 20-degree-of-freedom linear shear-type building. First, a preliminary linear shear-type model was derived by estimating the story stiffness so that the fundamental frequency matches that of the FE model. Then, an optimization problem is formulated and solved using a Genetic Algorithm (GA) combined with a weighted-sum method to achieve greater accuracy at higher frequencies in the preliminary model. Two objective functions were established and assessed for the optimization problem: one is the difference in frequencies between the FE model and the preliminary model with equal weighting, and the other is the first objective function improved with the modal participation percent weighting. The stiffness of each story in the preliminary model is selected as the design variable in both optimization problems. Finally, these optimized models are evaluated against the FE model using frequencies and dynamic time-history responses. The model derived from the weighted objective function demonstrates acceptable accuracy compared to its FE model in frequency and time-history analysis. It can be used for dynamic analysis and other structural and earthquake engineering purposes.
M. Fahimi Farzam, A. Ziamehr,
Volume 16, Issue 3 (7-2026)
Abstract
Considering the depletion of fossil fuel resources and their environmental impacts, offshore wind energy has emerged as a promising renewable solution. However, floating offshore wind turbines (FOWTs) are exposed to complex aerodynamic and hydrodynamic loads, particularly under combined wind and wave excitation, which can lead to excessive vibrations and fatigue damage. Therefore, effective vibration control strategies are essential to enhance structural reliability and durability. This study investigates the dynamic behavior and vibration mitigation of a floating offshore wind turbine supported by a Tension Leg Platform (TLP) under moderate, high, and extreme wind-wave conditions. A coupled model was developed using FAST-SC, and Multi-Tuned Mass Damper (MTMD) systems were implemented as passive control devices. The optimal MTMD parameters and installation layouts were determined, and their effectiveness in reducing tower and platform responses was evaluated. The results demonstrate that the optimized MTMD systems significantly improve the dynamic performance of the FOWT, achieving maximum reductions of 34% in tower fore-aft displacement, 43% in platform roll motion, and 41% in tower-base bending moment compared with the uncontrolled case. These reductions indicate the capability of MTMD systems to suppress structural vibrations, mitigate fatigue accumulation, and enhance the long-term reliability of offshore wind turbines. Consequently, the proposed approach has the potential to extend the service life of critical structural components and reduce maintenance requirements and life-cycle costs. This study provides valuable insights for the design of reliable and durable floating offshore wind turbines operating in harsh marine environments.
