| 1. |
- Heistermann, Tim, et al.
(author)
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Initial stiffness evaluation of reverse channel connections in tension and compression
- 2015
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In: Journal of constructional steel research. - : Elsevier BV. - 0143-974X .- 1873-5983. ; 114, s. 119-128
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Journal article (peer-reviewed)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. |
- Iqbal, Naveed, et al.
(author)
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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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In: Advanced steel construction. - 1816-112X. ; 12:2, s. 174-193
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Journal article (peer-reviewed)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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| 3. |
- Iqbal, Naveed, et al.
(author)
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Axial force and deformation of a restrained steel beam in fire: Description and validation of a simplified analytical procedure
- 2016
-
In: Advanced steel construction. - : Hong Kong Institute of Steel Construction. - 1816-112X. ; 12:2, s. 174-193
-
Journal article (peer-reviewed)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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| 4. |
- Iqbal, Naveed, et al.
(author)
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Numerical Investigation of the Behaviour of Steel Beams in Steel-Concrete Composite Frames
- 2016
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In: Composite Construction in Steel and Concrete VII. - New York : American Society of Civil Engineers (ASCE). - 9780784479735 ; , s. 199-213
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Conference paper (peer-reviewed)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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| 5. |
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| 6. |
- Iqbal, Naveed, et al.
(author)
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Numerical Study of Steel Beams in Sub-frame Assembly Validation of Existing Hand Calculation Procedures
- 2015
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In: Journal of Structural Fire Engineering. - : Emerald. - 2040-2317 .- 2040-2325. ; 6:2, s. 123-140
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Journal article (peer-reviewed)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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| 7. |
- Lopes, Fernanda, et al.
(author)
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Sub-frames with reverse channel connections to cft composite columns –experimental evaluation
- 2015
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In: Advanced steel construction. - : Hong Kong Institute of Steel Construction. - 1816-112X. ; 11:1, s. 111-126
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Journal article (peer-reviewed)abstract
- This paper presents the experimental results of the investigation on the coupled joint-structure behaviour of the composite sub-frame, using the reverse channel connections between an I-beam and the concrete filled tube (CFT) columns. This experimental programme includes seven full-scale tests: three tests at ambient temperature and four tests under heating-cooling curves. The parametric study was dedicated to: temperature-time curve and channel wall thickness (8, 10 and 12 mm). The main objective of these tests is to provide experimental information on the behaviour of the reverse channel joints and its influence on the structure under a heating-cooling fire. The restraining effects from the unaffected part of surrounding structure induce highly variable loading histories on the joints during fire; therefore the investigation on coupled joint-structure behaviour should lead to a realistic prediction of progressive collapse of the structure.
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| 8. |
- Pires, Ana Elisabete, et al.
(author)
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The curious case of the Mesolithic Iberian dogs : An archaeogenetic study
- 2019
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In: Journal of Archaeological Science. - : Elsevier BV. - 0305-4403 .- 1095-9238. ; 105, s. 116-129
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Journal article (peer-reviewed)abstract
- We investigated the genetic composition of six Canis remains from western Iberia, directly radiocarbon dated to 7,903-7,570 years (cal BP). They were identified as dogs via their archaeological and depositional context, osteometry, and a high percentage of aquatic diet shared with humans. For comparison, genetic data were obtained from an additional 37 Iberian dog remains from the Neolithic to Late Antiquity, as well as two Palaeolithic and a Chalcolithic Canis identified as wolves. Previous data indicated that dog mtDNA haplogroup A (HgA) is prevalent in extant European dogs ( > 50%), in the Near East and Asia, but rare or absent ( < 10%) in European Canis older than 3,000 years (cal BP). We found a high frequency (83%) of dog HgA in Mesolithic Iberian dog remains. This is the first report of a high frequency of dog HgA in pre-Neolithic Europe. We show that, contrary to the current view, Canis with HgA did not necessarily arrive in Europe from East-Asia. This phylogeographical difference in HgA frequency demonstrates that genetic differentiation was high prior to, or as a consequence of, domestication which may be linked with pre-Neolithic local processes for Iberian wolf domestication. Our results emphasize that knowledge of both ancient wolves' and early dogs' genetic profiles from the European periphery should improve our understanding of the evolution of the European dog.
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