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- 저자 : Fakhraddini (검색결과 3 건)
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A lateral load pattern based on energy evaluation for eccentrically braced frames
Ali Fakhraddini,Mohammad Javad Fadaee,Hamed Saffari 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.5
Performance-Based Plastic Design (PBPD) method has been recently developed to evaluate the behavior of structures in different performance levels. The PBPD method utilizes a base shear force and a lateral load pattern that are estimated based on energy and yielding mechanism concepts. Using of current lateral force pattern results in weak structural members in upper stories of a structure so that the values of the story drift in these stories are larger than the target drift, particularly in high-rise buildings. Therefore, such distribution requires modifications to overcome this drawback. This paper proposes a modified lateral load pattern for steel Eccentrically Braced Frames (EBFs) based on parametric study. In order toachieve the modified load pattern, a group of 26 EBFs has been analyzed under a set of 20 earthquake ground motions. Additionally, results of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to derive the new load pattern. To prove the efficiency of present study, three EBFs as examples were designed by modified pattern and current PBPD distribution. Inelastic dynamic analyses results showed that the story drifts using modified lateral load pattern were well within the target values in comparison with current pattern in PBPD, particularly where the effect of the height is significant. The modified load pattern reduces the possibility of underdesigning in upper levels and overdesigning in lower levels of the frames.
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A mathematical steel panel zone model for flanged cruciform columns
Hamed Saffari,Sina Sarfarazi,Ali Fakhraddini 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.4
Cruciform sections are an appropriate option for columns of orthogonal moment resisting frames for equal bending strength and stiffness about two main axes and the implementation is easier for continuity plates. These columns consist of two I-shaped sections, so that one of them is cut out in middle and two generated T-shaped sections be welded into I-shaped profile. Furthermore, in steel moment frames, unbalance moment at the beamcolumn connection leads to shear deformation in panel zone. Most of the obtained relations for panel zone strength derived from experimental and analytical results are on I-shaped columns with almost thin flanges. In this paper, a parametric study has been carried out using Finite Element Method (FEM) with effective parameters at the panel zone behavior. These parameters consist of column flange thickness, column web thickness, and thickness of continuity plates. Additionally, a mathematical model has been suggested to determine strength of cruciform column panel zone and has been shown its accuracy and efficiency.
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Local Flange Bending and Continuity Plate Requirements in Double-Web H-Shaped Columns
Reza Amani,Hamed Saffari,Ali Fakhraddini 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.1
In steel moment frames, columns are subjected to unbalance moment that is transmitted into the joint through a couple of concentrated forces at the centroid of the beam’s flanges. If the flexural capacity of the column flange is less than produced moment by these tensile or compressive forces, use of continuity plates in the panel zone is necessary. Since in box-shaped column, welding the forth edge of a continuity plate to the column flange may not be easily done and is usually accompanied by remarkable difficulties, double-web H-shaped columns as an appropriate alternative, which often do not require continuity plates, can be used. Numerous studies are carried out on local flange bending in H–shaped columns and are referred in the valid guidelines. The behavior of double-web column’s flange is between box shaped and H-shaped column’s flange. This paper presents analytical and numerical modeling of double web column to estimate local flange bending. The numerical modeling is derived from the results of finite element analyses. Based on these two approaches, some equations are presented to estimate local flange bending of double web columns, and are shown their efficiency and accuracy.
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