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RISS 인기검색어
- 검색키워드
- 저자 : Rezaifar, O. (검색결과 5 건)
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Analytical Study of Beam-to-HSS/CFT Column Connections by Trapezoidal External Stiffener
Omid Rezaifar,Adel Younesi 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2
Use of continuity plates in box columns is approved by design codes. To meet seismic parameters, considering performance problems and lack of confidence in the quality of the connections due to closed section, unsuitable vision and extreme welding and cutting at junction, continuity plates have been removed from the column and replaced by external stiffener. In this study, behavior of box beam-to-column connections with/without continuity plates, with external stiffener in two states with/without concrete (CFT/HSS) inside the column and finally reinforced connection by horizontal bar mats in CFT (Concrete Filled Tube) column have been studied by finite elements modeling and nonlinear analysis under monotonic and cyclic loadings. The results have shown that the use of external stiffener rather than continuity plate causes to increase 1% in rigidity and in turn 46.09% in strength. On the other hand, the use of filler concrete in column has caused to improve seismic behavior of the connection. When this connection containing the combination of external stiffeners and horizontal bar mats in CFT column is taken place, rigidity and strength parameters will be increased 3.01% and 108.8% respectively, compared to connections with no horizontal bar mats. In addition, the proposed connection has best performance in terms of both stress distribution and energy absorption and meets rigid connection criterion as well.
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Omid Rezaifar,Mohammad Nazari,Majid Gholhaki 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.5
Box sections are symmetrical sections and they have high moment of inertia in both directions, therefore they are good members in tall building structures. For the rigid connection in structures with box column continuity plates are used on level of beam flanges in column. Assembly of the continuity plates is a difficult and unreliable work due to lack of weld or high welding and cutting in the fourth side of column in panel zone, so the use of experimental stiffeners have been considered by researchers. This paper presented an experimental investigation on connection in box columns. The proposed connection has been investigated in four cases which contain connection without internal and external stiffeners(C-0-00), connection with continuity plates(C-I-CP), connection with external vase shape stiffener (C-E-VP) and connection with surrounding plates(C-ESP). The results show that the connections with vase plates and surrounding plates can respectively increase the ultimate strength of the connection up to 366% and 518% than the connection without stiffeners, in case connection with the continuity plates this parameter increases about 39%. In addition, the proposed C-E-VP and C-E-SP connection provide a rigid and safe connection to acquire rigidity of 95% and 98% respectively. But C-I-CP connection is classified as semi-rigid connections.
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Younesi, Adel,Rezaifar, Omid,Gholhaki, Majid,Esfandiari, Akbar Techno-Press 2021 Structural monitoring and maintenance Vol.8 No.1
In recent years, damage detection methods have been significantly increased in civil and mechanical structures. One of the most widely used and relatively new methods of signal processing is the method based on wavelet transform; with the help of this powerful tool, the damage in the structures can be detected in the early stages of damage formation, in order to prevent a larger damage event. In this paper, we have investigated the debonding damage of active surfaces in Concrete-Filled Tube (CFT) columns, which greatly reduces the effect of enclosure on concrete and decreases the bearing capacity of these tubes with the help of wavelet transformation (Discrete Wavelet Transform and Continuous Wavelet Transform). The debonding damage of the active surfaces was evaluated using wavelet types, and the occurrence and location of the damage were detected based on variations in frequency and mode shapes. The above studies have been done for the first six modes of the CFT column. The results of the analyzes indicate that the wavelet transform tool is very capable of detecting the occurrence and location of the damage and is able to detect high-level debonding damage in one side of the column that creates curvature and slight jump in the shape of the mode.
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Adel Younesi,Omid Rezaifar 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.1
The use of box columns has been increased due to the rigidity in rigid orthogonal moment resisting frames. On the other hand, the installation and welding of necessary horizontal continuity plates inside the columns are both labor-consuming and costly tasks. Accordingly, in this paper, a new beam-to-box column connection by trapezoidal external stiffeners and horizontal bar mats is presented to provide seismic parameters. The proposed connection consists of eight external stiffeners in the level of beam flanges and five horizontal bar mats in Concrete Filled Tube (CFT) columns. The new connection effectively alleviates the stress concentration and moves the plastic hinge away from the column face by horizontal external stiffeners. In addition, the result shows that proposed connection has provided the required strength and rigidity of connection, so that the increased strength, 8.08% and rigidity, 3.01% are compared to connection with internal continuity plates, also the results indicate that this connection can offer appropriate ductility and energy dissipation capacity for its potential application in moment resisting frames in seismic region. As a result, the proposed connection can be a good alternative for connection with continuity plates.
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Upgrading flexural performance of prefabricated sandwich panels under vertical loading
Kabir, M.Z.,Rezaifar, O.,Rahbar, M.R. Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.26 No.3
3-D wall panels are used in construction of exterior and interior bearing and non-load bearing walls and floors of building of all types of construction. Fast construction, thermal insulation, reduced labor expense and weight saving are the most well pronounced advantage of such precast system. When the structural performance is concerned, the main disadvantage of 3D panel, when used as floor slab, is their brittleness in flexure. The current study focuses on upgrading ductility and load carrying capacity of 3D slabs in two different ways; using additional tension reinforcement, and inserting a longitudinal concentrated beam. The research is carried on both experimentally and numerically. The structural performance in terms of load carrying capacity and flexural ductility are discussed in details. The obtained results could give better understanding and design consideration of such prefabricated system.
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