http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Mohammad Amir Najafgholipour (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
-
A numerical study on the plastic rotation capacity of CFRP-confined rectangular RC columns
Mohammad Amir Najafgholipour,Seyed Mohammad Javad Zahabi 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.6
To perform a nonlinear analysis of building frames in their seismic performance evaluation program, appropriate force-deformation curves of the structural members in linear and nonlinear phases which represent their actual behavior are required. Although these curves have been provided for common existing RC elements prior to retrofitting in available instructions, the codes are silent about appropriate practical models for strengthened elements. In this regard, a comprehensive numerical study is conducted in the Finite Element (FE) software VecTor2 to investigate the effects of various influential parameters on the moment-rotation behavior of CFRP-confined rectangular RC columns. The investigated parameters are cross-sectional dimensions, longitudinal and transverse reinforcement ratios, the level of column axial load, concrete compressive strength, and the effective confinement provided by external CFRP wraps. Then, through the idealization of the obtained moment-rotation curves, the influence of the aforementioned parameters on the plastic rotation capacity of the columns as one of the main required parameters to define the nonlinear behavior of the retrofitted columns is investigated. Accordingly, column axial load intensity, shear force, effective confinement, and column depth are found to be the major effective parameters on the plastic rotation capacity of the columns. Finally, a practical method consistent with ASCE 41-13 is presented to estimate the plastic rotation capacity of CFRP-confined columns.
-
Amir Tabebordbar,Seyed Mehdi Dehghan,Farshid Fathi,Mohammad Amir Najafgholipour 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.5
Built-up Double-I (BD-I) columns have been commonly used for mid-rise steel-frame structures in Iran. These columns consist of two hot rolled IPE sections which are connected by two cover plates and fillet welds. Until 2017, BD-I columns were employed in intermediate moment resisting frames (MRF) using welded flange plate (WFP) connections. To evaluate the seismic behavior of the connections, four samples were made and tested based on cyclic loading according to AISC 341-16. It was concluded that typical samples cannot satisfy the seismic provisions related to intermediate MRFs. In contrast, the proposed connections retrofitted with two-part external diaphragms were able to satisfy not only the seismic requirements related to intermediate MRFs but also those related to special MRFs according to AISC. The numerical modeling of these samples was performed using ABAQUS finite element software. This study compared the hysteresis moment-rotation curves, plastic strains, and behavior modes in both experimental samples and numerical models.
-
Seyed Mehdi Dehghan,Mohammad Amir Najafgholipour,Seyed Mohsen Ziarati,Mohammad Reza Mehrpour 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3
Built-up Double-I (BD-I) columns consist of two hot rolled IPE sections and two cover plates which are welded by fillet welds. In Iran, this type of column is commonly used in braced frames with simple connections and sometimes in low-rise Moment Resisting Frames (MRF) with Welded Flange Plate (WFP) beam-column detailing. To evaluate the seismic performance of WFP connection of I-beam to BD-I column, traditional and modified exterior MRF connections were tested subjected to cyclic prescribed loading of AISC. Test results indicate that the traditional connection does not achieve the intended behavior while the modified connection can moderately meet the requirements of MRF connection. The numerical models of the connections were developed in ABAQUS finite element software and validated with the test results. For this purpose, moment-rotation curves and failure modes of the tested connections were compared with the simulation results. Moreover to avoid improper failure modes, some improvements of the connections were evaluated through a numerical study.
-
Majid Khayat,Abdolhossein Baghlani,Seyed Mehdi Dehghan,Mohammad Amir Najafgholipour 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.1
This work addresses the free vibration analysis of Functionally Graded Porous (FGP) nanocomposite truncated conical shells with Graphene PLatelet (GPL) reinforcement. In this study, three different distributions for porosity and three different dispersions for graphene platelets have been considered in the direction of the shell thickness. The Halpin–Tsai equations are used to find the effective material properties of the graphene platelet reinforced materials. The equations of motion are derived based on the higher-order shear deformation theory and Sanders’s theory. The Fourier Differential Quadrature (FDQ) technique is implemented to solve the governing equations of the problem and to obtain the natural frequencies of the truncated conical shell. The combination of FDQ with higher-order shear deformation theory allows a very accurate prediction of the natural frequencies. The precision and reliability of the proposed method are verified by the results of literature. Moreover, a wide parametric study concerning the effect of some influential parameters, such as the geometrical parameters, porosity distribution, circumferential wave numbers, GPLs dispersion as well as boundary restraint conditions on free vibration response of FGP-GPL truncated conical shell is also carried out and investigated in detail.
-
Majid Khayat,Seyed Mehdi Dehghan,Mohammad Amir Najafgholipour,Abdolhossein Baghlani 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.6
In this study, the semi-analytical finite strip method is adopted to examine the free vibration of cylindrical shells made up of functionally graded material. The properties of functionally graded shells are assumed to be temperature-dependent and vary continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of ceramic and metal. The material properties of the shells and stiffeners are assumed to be continuously graded in the thickness direction. Theoretical formulations based on the smeared stiffeners technique and the classical shell theory with first-order shear deformation theory which accounts for through thickness shear flexibility are employed. The finite strip method is applied to five different shell theories, namely, Donnell, Reissner, Sanders, Novozhilov, and Teng. The approximate procedure is compared favorably with three-dimensional finite elements. Finally, a detailed numerical study is carried out to bring out the effects of power-law index of the functional graded material, stiffeners, and geometry of the shells on the difference between various shell theories. Finally, the importance of choosing the shell theory in simulating the functionally graded cylindrical shells is addressed.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
