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- 저자 : Ahmed Rahmani (검색결과 4 건)
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Ahmed M. Abd El-Fattah,Hayder A. Rasheed,Ahmed H. Al-Rahmani 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.1
The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value fcc (at zero eccentricity) to the unconfined value f 0 c (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of P–e and M–u response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.
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Abd El Fattah, Ahmed M.,Rasheed, Hayder A.,Al-Rahmani, Ahmed H. Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.1
The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value $f_{cc}$ (at zero eccentricity) to the unconfined value $f^{\prime}_c$ (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of $P-{\varepsilon}$ and $M-{\varphi}$ response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.
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Aperiodically Intermittent Adaptive Event-triggered Control for Linear Multi-agent Systems
Yunlong Zhang,Guoguang Wen,Ahmed Rahmani,Xiaoqin Zhai 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.1
This paper investigates the aperiodically intermittent adaptive event-triggered control strategy for general linear multi-agent systems. The aperiodically intermittent adaptive event-triggered control inherits the respective advantages of aperiodically intermittent control strategy, event-triggered control strategy and adaptive control strategy, which improves communication efficiency, reduces control update frequency and is closer to the practical situations. Firstly, to reach leader-following consensus and save more control resources, a distributed aperiodically intermittent event-triggered scheme is devised, in which the transmission channels among agents only open if the local event-trigger condition is satisfied in predefined time intervals. Then, in order to get rid of continuous inter-agent communication for monitoring the triggering condition, a more general triggering mechanism is presented, in which discrete-time combinational measurement is adopted instead of using continuous-time tracking error directly. Next, to overcome the unexpected large feedback gains in real applications and appropriately tune the feedback gains, the aperiodically intermittent adaptive event-triggered controller is further devised. With aid of the matrix theory, stability theory of switching systems and Lyapunov function, some sufficient criteria are deduced. Moreover, the analyses of excluding the Zeno behavior are included, and explicit positive lower bounds between any two consecutive time intervals are rigorously guaranteed. Finally, the effectiveness for the designed control strategies is validated by simulations.
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Jing Bai,Guoguang Wen,Yu Song,Ahmed Rahmani,Yongguang Yu 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.1
The distributed formation control of fractional-order multi-agent systems is mainly studied under directedcommunication graphs in this paper. Firstly, a control law with relative damping and communication delay areproposed. Then, some sufficient conditions for achieving formation control are derived using matrix theory, graphtheory and the frequency domain analysis method. Finally, based on the numerical method of predictor-corrector,several simulations are presented to illustrate the effectiveness of the obtained results.
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