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RISS 인기검색어
- 검색키워드
- 저자 : Mohammad Khanmohammadi (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Cyclic load testing and numerical modeling of concrete columns with substandard seismic details
Mohammad K. Bahrani,Mohammad S. Marefat,Mohammad Khanmohammadi,Ali Goli 한국계산역학회 2005 Computers and Concrete, An International Journal Vol.2 No.5
Recent earthquakes have shown that many of existing buildings in Iran sustain heavy damage due to defective seismic details. To assess vulnerability of one common type of buildings, which consists of low rise framed concrete structures, three defective and three standard columns have been tested under reversed cyclic load. The substandard specimens suffered in average 37% loss of strength and 45% loss of energy dissipation capacity relative to standard specimens, and this was mainly due to less lateral and longitudinal reinforcement and insufficient sectional dimensions. A relationship has been developed to introduce variation of plastic length under increasing displacement amplitude. At ultimate state, the length of plastic hinge is almost equal to full depth of section. Using calibrated hysteresis models, the response of different specimens under two earthquakes has been analyzed. The analysis indicated that the ratio between displacement demand and capacity of standard specimens is about unity and that of deficient ones is about 1.7.
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Stability of Nonlinear Hybrid Dynamical Systems with Time Delay via Sum of Squares Decomposition
Mohammad Ali Badamchizadeh,Sohrab Khanmohammadi,Gasem Alizadeh,Ali Aghagolzadeh 제어·로봇·시스템학회 2009 International Journal of Control, Automation, and Vol.7 No.3
Considering an infinite number of eigenvalues for time delay systems, it is difficult to determine their stability. We have developed a new approach for the stability test of time delay nonlinear hybrid systems. Construction of Lyapunov functions for hybrid systems is generally a difficult task, but once these functions are found, stability’s analysis of the system is straight-forward. In this paper both delay-independent and delay-dependent stability tests are proposed, based on the construction of ap-propriate Lyapunov-Krasovskii functionals. The methodology is based on the sum of squares decom-position of multivariate polynomials and the algorithmic construction is achieved through the use of semidefinite programming. The reduction techniques provide numerical solution of large-scale in-stances; otherwise they will be computationally infeasible to solve. The introduced method can be used for hybrid systems with linear or nonlinear vector fields. Finally simulation results show the correct-ness and validity of the designed method.
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Mohammadreza Khanmohammadi,Amir Bagheri Garmarudi,Hamideh Elmizadeh,Mohammad Babaei Roochi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4
Photocatalytic capabilities of sol–gel synthesized Fe2O3–TiO2 nano hybrid was investigated in degradation of formaldehyde in presence of ultra violet and visible irradiation. The reaction stream was evaluated by UV–vis spectrophotometry at 330–500 nm spectral region, using Fluoral-P (4-amino-3-penten-2-one) as a complexing agent. Obtained results confirmed the effective role of Fe2O3 phase in nano hybrid for degradation of formaldehyde according to Baeyer–Villiger reaction. On the other hand TiO2 would play the role of photocatalyst in presence of UV ray. Nano hybrid assisted process was monitored by spectrophotometry, utilizing multivariate curve resolution chemometric technique.
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Novel plastic hinge modification factors for damaged RC shear walls with bending performance
Komarizadehasl, Seyedmilad,Khanmohammadi, Mohammad Techno-Press 2021 Advances in concrete construction Vol.12 No.4
This paper introduces several new damage states for shear walls with flexural behavior damaged in an earthquake. These damage states are deducted by carefully interpretation of reported available test results of shear walls in the literature. Moreover, two methods for obtaining the plastic hinge modification factors of strength, stiffness and ductility capacity of the damaged shear walls with the flexural behavior are presented. A method based on secant stiffness at maximum displacement of each cycle of observed damage and the second method uses the reloading stiffness of the hysteresis curves consistent with damage levels. The later method introduced in this research is more reasonable for obtaining modification factors among the introduced methods. Using these factors, a reliable residual capacity for damaged structures can be assessed and the proper seismic retrofitting method can be followed. In this research, the effects of damages caused by various experimental tests have been studied on 43 reinforced concrete shear walls with flexural behavior. By introducing and describing the bending performance's damage levels, given the shear wall's observable condition such as cracks' width, concrete spalling and crushing, conditions of longitudinal and transvers rebars, 10 damage levels are introduced. The factors of modification of stiffness, strength, and the acceptable range of ductility of the member (𝜆k, 𝜆Q, and 𝜆D) were proposed for each level of damage. The results show that almost across all damage levels, the damage grew with increased drift. Nonetheless, stiffness and ductility modification factors are constant during the first damage states; they decrease dramatically after the third damage state (DS4). However, the reduction of the strength decreased gradually as of the fourth damage state. the results presented in current research are more reliable estimation of reduction factors in comparison with current approaches.
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A Hierarchical Fuzzy System for Modeling Driver’s Behavior
Sehraneh Ghaemi,Sohrab Khanmohammadi,Mohammad Ali Tinati,Mohammad Ali Badamchizadeh 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.3
The study of human behavior during driving is of primary importance for improving the driver’s security. In this study, we propose a hierarchical driver_vehicle_environment fuzzy system to analyze driver’s behavior under stress conditions on a road. We include climate, road and car conditions in fuzzy modeling. For obtaining fuzzy rules, experts’ opinions are benefited by means of questionnaires on effects of parameters such as climate, road and car conditions on driving capabilities. The number of fuzzy rules is optimized by Particle Swarm Optimization (PSO) algorithm. Also the frequency of pressing on brake and gas pedals and the number of car’s direction changes are used to determine the driver’s behavior under different conditions. Three different positions are considered for driving and decision making; one position in driving lane and two positions in opposite lane. A fuzzy model called Model 1 is presented for modeling the change of steering angle and speed control by considering time distances with existing cars in these three positions, the information about the speed and direction of car, and the steering angle of car. The behaviors of different drivers under two stress conditions are investigated. Also we obtained two other models based on fuzzy rules called Model 2 and Model 3 by using Sugeno fuzzy inference. Model 2 has two linguistic terms and Model 3 has four linguistic terms for estimating the time distances with other cars. The results of three models are compared. The com-parative studies have shown that simulation results are in good agreement with the real world situa-tions.
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