| 1. |
- Heistermann, Tim, et al.
(författare)
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Initial stiffness evaluation of reverse channel connections in tension and compression
- 2015
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Ingår i: Journal of constructional steel research. - : Elsevier BV. - 0143-974X .- 1873-5983. ; 114, s. 119-128
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Tidskriftsartikel (refereegranskat)abstract
- The so-called Reverse Channel connection has been conceived for the purpose of accommodating the thermal expansion of beams so that premature failure due to thermal buckling is avoided. The connection is made of a channel-shaped element, welded along the tips of its flanges onto the face of a hollow section column; an endplate welded on the beam is bolted onto the web of the channel. In a fire situation, the thermal expansion of a reverse-channel supported beam causes extensive bending deformation of the connection, therefore preventing the development of significant axial stress in the beam. Furthermore, this connection offers a high rotational capacity, if designed properly, which is beneficial in a fire situation where excessive deflections of beams can be expected. This paper aims to provide analytical stiffness assessment tools for reverse channel connections in compression and tension under uniform temperatures. The proposed analytical models are compared to results of Finite Element simulations, which in turn have been benchmarked with experiments. In addition, a comprehensive parametric study is conducted in order to identify all influencing factors on the initial stiffness response: reverse channel geometry and thickness, plate thickness, bolt position, and bolt diameter. Correction factors that account for 3D effects and bolt size are presented and discussed. The obtained expressions for the reverse channel stiffness are found to provide an accuracy that is acceptable for structural applications and can, therefore, be used as a design tool.
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| 2. |
- Heistermann, Tim, et al.
(författare)
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Initial Stiffness of Reverse Channel Connections
- 2014
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Ingår i: Eurosteel 2014. - Brussels : European Convention for Constructional Steelwork, ECCS. - 9789291471218
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Konferensbidrag (refereegranskat)abstract
- The robustness of a structure in a fire situation greatly depends on the rotational capacity of the connection region. High rotational capacity is required at elevated temperatures since the steel beams lose their bending stiffness and exhibit increasingly large deflections under constant load. Beam deflections result in increasing rotations at the supports and may lead to collapse due to connection failure. The reverse channel has been proposed as a practical alternative to assemble beams to tubular columns. In a simple implementation, the bending moment generated in the joint due to rotation of the beam may be neglected; however, research efforts are being attempted to quantify the level of constraint. The typical arrangement of the connection type consists of a reverse channel with its flanges welded onto the face of concrete-filled tubular columns and the web bolted to the endplate of a beam. Thicknesses and depths of the reverse channel determine the level of rotational restraint at high temperature. The reverse channel has the ability to undergo catenary deformation in the tensile zone due to the applied rotation at the support and similarly it is relatively ductile in the compression zone. Overall, the reverse channel connection response is rather ductile in terms of its ability to undergo large rotational deformation as long as bolt failure is avoided through proper design.Various tests have been performed to study the behaviour of this type of connection such as full scale buildings, sub-frames, isolated joints and individual sections. The aim of these tests was to capture the connection behaviour in relation to other structural components in fire. This paper, however, focuses on the derivation and verification of analytical models to assess the initial stiffness of reverse channel/partial-depth endplate connections. The results from finite element analyses have been utilized to validate analytical models that describe the behaviour of this type of connection at ambient and elevated temperature. Insight into the analytical models provides proper background to a structural designer to estimate the initial stiffness and understand the behaviour of the reverse channel in the connection.
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| 3. |
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| 4. |
- Iqbal, Naveed, et al.
(författare)
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Axial Force And Deformation Of A Restrained Steel Beam In Fire : Description and validation of a simplified analytical procedure
- 2016
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Ingår i: Advanced steel construction. - 1816-112X. ; 12:2, s. 174-193
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Tidskriftsartikel (refereegranskat)abstract
- Structural fire design is exceedingly adopting the performance based approach. There are evidentadvantages of this approach compared to the prescriptive methods from codes. An analytical procedure, based on thereal performance, must accurately predict the beam behaviour in fire. The study presented here proposes one suchsimplified analytical procedure aim to predict the real behaviour of a restrained steel beam. The proposed analyticalprocedure is validated through FE Analysis using FE models validated through test results. The study also attempts toestablish the importance of using semi-rigid connection strength with respect to accurately predicting the behaviorof the restrained beam at catenary stage.
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| 5. |
- Iqbal, Naveed, et al.
(författare)
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Axial force and deformation of a restrained steel beam in fire: Description and validation of a simplified analytical procedure
- 2016
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Ingår i: Advanced steel construction. - : Hong Kong Institute of Steel Construction. - 1816-112X. ; 12:2, s. 174-193
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Tidskriftsartikel (refereegranskat)abstract
- Structural fire design is exceedingly adopting the performance based approach. There are evident advantages of this approach compared to the prescriptive methods from codes. An analytical procedure, based on the real performance, must accurately predict the beam behaviour in fire. The study presented here proposes one such simplified analytical procedure aim to predict the real behaviour of a restrained steel beam. The proposed analytical procedure is validated through FE Analysis using FE models validated through test results. The study also attempts to establish the importance of using semi-rigid connection strength with respect to accurately predicting the behaviour of the restrained beam at catenary stage.
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| 6. |
- Iqbal, Naveed, et al.
(författare)
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Numerical Investigation of the Behaviour of Steel Beams in Steel-Concrete Composite Frames
- 2016
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Ingår i: Composite Construction in Steel and Concrete VII. - New York : American Society of Civil Engineers (ASCE). - 9780784479735 ; , s. 199-213
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Konferensbidrag (refereegranskat)abstract
- The methods proposed by the design codes for single member design in fire situation assume that these members are isolated in their response. The real response of structural members such as beams is, however, more complex due to thermal expansion and the presence of restraints against this expansion by the surrounding structure. It is therefore imperative to study the response of structure at high temperature in a way which includes its interaction with its surroundings such as in a full-scale fire test and in numerical analysis. This paper focuses on the numerical investigation of steel beams, with a concrete slab and connected to concrete filled tubular (CFT) columns through reverse channel connections. The finite element software ABAQUS has been used in this study. The aim of the investigation is to study the behaviour of the composite steel-concrete beam exposed to increasing temperature in fire.
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| 7. |
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| 8. |
- Iqbal, Naveed, et al.
(författare)
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Numerical Study of Steel Beams in Sub-frame Assembly Validation of Existing Hand Calculation Procedures
- 2015
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Ingår i: Journal of Structural Fire Engineering. - : Emerald. - 2040-2317 .- 2040-2325. ; 6:2, s. 123-140
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Tidskriftsartikel (refereegranskat)abstract
- The design methods currently proposed by the codes prescribe the strength assessment of structures to be based on their strength limit state. These design methods can be applied to isolated steel members to determine their design strengthin fire. The real response of a structural member is, however, more complex due to the thermal expansion and the presence of restraints against this expansion by the surrounding structure. It is therefore imperative to study the response of a structural member at high temperature in a way which includes its interaction with its surroundings. This paper focus on the numerical investigation of steel beams in structural frames connected to concrete filled tubular (CFT) columns through reverse channel connections and comparison to hand calculation procedures. Finite element models (FEM) of the sub-frames were validated against fire tests conducted on sub-frames and then their results were compared to the proposed simplified hand calculation procedures (HCM).
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| 9. |
- Iqbal, Naveed
(författare)
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Restrained behaviour of beams in steel frames exposed to fire
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The current design procedures prescribed by the codes for design of steel beams at elevated temperatures require that the ultimate flexural resistance of the beam should be checked against the applied loading. This approach does not take into account the redistribution of bending moment due to fire exposure that takes place in a redundant frame. The axial and rotational restraints at the beam to column connections in such a frame play an important role as to how the beam behaves in restrained conditions when exposed to fire. This is particularly important at relatively high temperatures when the beam has undergone significant deflections and as the catenary action in the beam gradually takes over as the resisting mechanism beyond the limiting temperature prescribed by the codes.Simplified design procedures that satisfactorily describe the restrained beam behaviour should be used to avoid the high cost and complexity of finite element analysis and fire tests. A proposed simplified design procedure has been used to analyse axially and rotationally restrained beams in sub-frames in this study and the results are compared to the results from their finite element models. The finite element models of the sub-frames were validated against fire tests conducted on sub-frames. The proposed method was shown to have satisfactorily predicted the restrained beam behaviour under different load levels and temperature distributions.The validated finite element models were also used to investigate the effect of changing different parameters of the sub-frame, such as temperature distribution, boundary conditions and fire protection on the connection region. The distribution of strains in the connection components were shown to have been significantly affected by changing these parameters.
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| 10. |
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