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RISS 인기검색어
- 검색키워드
- 저자 : Mostofinejad, Davood (검색결과 3 건)
- 무료
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Moosaie Iman,Mostofinejad Davood,Shojaee Saeed 한국물리학회 2022 Current Applied Physics Vol.36 No.-
Although the classical continuum theory is advantageous in finding solutions to a wide range of engineering problems, it cannot describe some phenomena such as dispersion of acoustic waves, effects of surfaces and interfaces on the mechanical behavior of small-scale structures, and microstructure contribution in special materials. Owing to this fact, several enhanced continuum theories have evolved in the literature. However, the difficulty in determination of the length scale parameters that appear in the governing equations of such theories hampers their widespread use in practice. To date, except for a very limited number of materials, there is no known experimental procedure for the identification of these parameters. In this research, the internal length scales for an augmented continuum theory, i.e., Mindlin’s strain gradient theory, have been theoretically determined for some crystalline materials with cubic structure that are of engineering interest, using ab initio DFT. According to the values obtained for these parameters, it can be perceived that the strain gradient theory is a valuable tool for capturing the size effects at even the smallest scales comparable to the dimensions of a unit cell of a crystal lattice.
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Experimental study on effect of EBRIG shear strengthening method on the behavior of RC beams
Shomali, Amir,Mostofinejad, Davood,Esfahani, Mohammad Reza Techno-Press 2019 Advances in concrete construction Vol.8 No.2
The present experimental study addresses the structural response of reinforced concrete (RC) beams strengthened in shear. Thirteen RC beams were divided into four different sets to investigate the effect of transverse and longitudinal steel reinforcement ratios, concrete compressive strength change and orientation for installing carbon fiber-reinforced polymer (CFRP) laminates. Then, we employed a shear strengthening solution through externally bonded reinforcement in grooves (EBRIG) and externally bonded reinforcement (EBR) techniques. In this regard, rectangular beams of $200{\times}300{\times}2000mm$ dimensions were subjected to the 4-point static loading condition and their load-displacement curves, load-carrying capacity and ductility changes were compared. The results revealed that using EBRIG method, the gain percentage augmented with the increase in the longitudinal reinforcement ratio. Also, in the RC beams with stirrups, the gain in shear strength decreased as transverse reinforcement ratio increased. The results also revealed that the shear resistance obtained by the experimental tests were in acceptable agreement with the design equations. Besides, the results of this research indicated that using the EBRIG system through vertical grooves in RC beams with and without stirrups caused the energy absorption to increase about 85% and 97%, respectively, relative to the control.
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FE analysis of RC structures using DSC model with yield surfaces for tension and compression
A.H. Akhaveissy,C.S. Desai,D. Mostofinejad,A. Vafai 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.2
The nonlinear finite element method with eight noded isoparametric quadrilateral element for concrete and two noded element for reinforcement is used for the prediction of the behavior of reinforcement concrete structures. The disturbed state concept (DSC) including the hierarchical single surface (HISS) plasticity model with associated flow rule with modifications is used to characterize the constitutive behavior of concrete both in compression and in tension which is named DSC/HISS-CT. The HISS model is applied to shows the plastic behavior of concrete, and DSC for microcracking, fracture and softening simulations of concrete. It should be noted that the DSC expresses the behavior of a material element as a mixture of two interacting components and can include both softening and stiffening, while the classical damage approach assumes that cracks (damage) induced in a material treated acts as a void, with no strength. The DSC/HISS-CT is a unified model with different mechanism, which expresses the observed behavior in terms of interacting behavior of components; thus the mechanism in the DSC is much different than that of the damage model, which is based on physical cracks which has no strength and interaction with the undamaged part. This is the first time the DSC/HISS-CT model, with the capacity to account for both compression and tension yields, is applied for concrete materials. The DSC model allows also for the characterization of non-associative behavior through the use of disturbance. Elastic perfectly plastic behavior is assumed for modeling of steel reinforcement. The DSC model is validated at two levels: (1) specimen and (2) practical boundary value problem. For the specimen level, the predictions are obtained by the integration of the incremental constitutive relations. The FE procedure with DSC/HISS-CT model is used to obtain predictions for practical boundary value problems. Based on the comparisons between DSC/HISS-CT predictions, test data and ANSYS software predictions, it is found that the model provides highly satisfactory predictions. The model allows computation of microcracking during deformation leading to the fracture and failure; in the model, the critical disturbance, Dc, identifies fracture and failure.
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