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  • 1.
    Cheng, Xudong
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Byström, Alexandra
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sandström, Joakim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Prediction of temperature variation in an experimental building2011In: Proceedings of International Conference Applications of Structural Fire Engineering: Prague, 29 April 2011, 2011, p. 387-392Conference paper (Refereed)
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  • 2. Dogar, Attiq Ur Rahman
    et al.
    Rehman, Hafiz Muhammad Ubaid Ur
    ISISE – Institute for Sustainability and Innovation in Structural Engineering, University of Coimbra.
    Tafsirojjaman, T.
    School of Civil Engineering and Built Environment, Faculty of Science and Engineering, Queensland University of Technology.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Experimental investigations on inelastic behaviour and modified Gerber joint for double-span steel trapezoidal sheeting2020In: Structures, ISSN 2352-0124, Vol. 24, p. 514-525Article in journal (Refereed)
    Abstract [en]

    Cold-formed steel trapezoidal profiles provide efficient solutions for roofing and often use the Gerber joint to effectively utilize capacities. The previous design of Gerber joint was sensitive to uneven distribution of loads and accidental loads, which imposed bending moments in the joint and lead to its failure. In this experimental program, the design of Gerber joint has been modified to work as a hinge under service loads and carry moments in accidental conditions. Also, the design of CFS is based on elastic methods that underestimate their capacity, especially for multi-span systems. Full-scale tests were conducted on highly stiffened double-span trapezoidal sheeting profiles with modified Gerber joint to investigate elastic capacity, inelastic behaviour, moment redistribution in the post-elastic phase, ultimate load capacity and feasibility of modified Gerber joint. Comparison of elastic load capacity with EWM and DSM predictions revealed that EWM design predictions were conservative by 30% while DSM predictions were accurate. For multi-span application, residual moment capacity ratios of 0.76 and 0.81 in the post-elastic phase allowed for moment redistribution and increased ultimate load capacity by 7.14% and 8.80% for 0.85 mm and 1 mm thick profiles respectively. Performance of modified Gerber joint to behave as a hinge under service loads and as continuous in the post-elastic phase was also found to be satisfactory. The study concluded that the economy in design and capacity utilization of multi-span CFS profiles can be improved by allowing for moment redistribution and using the modified Gerber joint.

  • 3.
    Heistermann, Tim
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    University of Coimbra, Department of Civil Engineering.
    Silva, Luís Simões da
    University of Coimbra, Department of Civil Engineering.
    Reverse channel connections at elevated temperature: finite element modelling2011In: Proceedings of the 6th European Conference on Steel and Composite Structures: Eurosteel 2011, August 31 - September 2, 2011, Budapest, Hungary, Budapest: European Convention for Constructional Steelwork, ECCS , 2011, p. 1587-1592Conference paper (Refereed)
  • 4.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Analysis of Catenary Effect in Steel Beams and Trusses Exposed to Fire2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The goals of structural design are fundamentally different when designing structures at normal temperature or when designing them in a fire situation. While structures are primarily designed for normal temperature situations considering the different design limit states, in the fire design situation, however, the already designed structure is assessed for its resistance in the fire design limit state. The assessment of the structure in the fire limit state may lead to either active or passive fire protection measures. The assessment of the structure in fire may be done in several different domains such as its structural resistance, integrity of structural components to prevent spread of fire and insulation properties of materials. The focus of the thesis presented here is on the structural resistance of steel structural members particularly steel beams and trusses in fire situations.The Eurocodes permit designers to use either a simple prescriptive design procedure or a more complex performance based procedure for design of structures in fire. The prescriptive design is a simple choice regarding design of steel structures in fire due to their use of simple analytical equations; but through several studies it has been established that this approach might be conservative and in some situations it might not reflect the complexity of interaction between the heated structural members and its surrounding colder parts of the structure. The performance based approach has therefore been increasingly adopted in structural fire design, which, although more complex than the prescriptive approach, is closer to the real structural behaviour.Through a performance based approach, this thesis aims to establish that steel structural members are able to offer structural resistance in fire situations that are much higher than would be expected from a prescriptive approach. Two different types of structural members such as steel beams in multi-storey buildings and trusses in single storey buildings were considered here. It has been shown through extensive finite element analysis in both cases that actual resistance of these structural members in fire situations can exceed their primary resistance mechanism through flexure. Alternative load transfer mechanism through catenary action offers the added resistance at much higher temperatures than the conventional critical temperatures from prescriptive design. The thesis also proposes simplified calculation procedures that can be used to reasonably predict the structural resistance at elevated temperatures considering the catenary action.

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  • 5.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restrained behaviour of beams in steel frames exposed to fire2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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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  • 6.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Fodor, Jovan
    Czech Technical University, Prague.
    Sandström, Joakim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Veljkovic, Milan
    Delft University of Technology.
    Catenary action in single storey industrial halls subjected to localized fires2017In: Proceedings of the 7th International Conference on Mechanics and Materials in Design (M2D) / [ed] Gomes, JFS; Meguid, SA, Porto: INEGI-FEUP , 2017, p. 1627-1628Conference paper (Refereed)
    Abstract [en]

    This paper reports on the results from extensive finite element study of single storey industrial halls subjected to the action of localized fires. The results show offer structural resistance in fire situations that are much higher than would be expected from a prescriptive approach. It has been shown that actual resistance of these structural members in fire situations can exceed their primary resistance mechanism through flexural action only. Alternative load transfer mechanism through catenary action offers the added resistance at much higher temperatures than the conventional critical temperatures from prescriptive design. The paper also presents simplified calculation procedures that can be used to reasonably predict the structural resistance at elevated temperatures considering the catenary action

  • 7.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Gervasio, H.
    Universidade de Coimbra.
    Eriksen, J.
    Luleå tekniska universitet.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Silva, L. Simoes da
    Universidade de Coimbra.
    Inflation adjusted LCCA of a comparative study of an Integral abutment bridge and a Concrete bridge with expansion joints2010In: Sustainable construction - a life cycle approach in engineering: Proceedings, International Symposium Malta, 23 - 25 July 2010. COST Action C25, 2010, p. 151-161Conference paper (Refereed)
    Abstract [en]

    Gervasio H. et al [1]in there comparative life cycle analysis of an integral abutment composite bridge and concrete bridge have established the advantages of integral bridge due to its limited initial construction cost and maintenance and repair costs during its life cycle. This paper is based on the same data with a modification to the life cycle cost analysis of the bridge by using an inflation adjusted discount rate. In standard bridge structures, expansion joints are one of the most expensive components to maintain. In this regard, joint less bridge have major advantages. Integral bridges are built without joints, they span from one abutment to the other abutment, possibly over intermediate piers, without any joints in the deck. The absence of joints and bearings results in savings in initial costs and reduce maintenance efforts. Apart from economic benefits, the reduction of maintenance leads to less disturbance of the traffic over the bridge and thus to smaller environmental and social impacts. In this paper a case study is presented with the purpose of making a comparative life cycle analysis between an integral composite bridge and a concrete bridge with expansion joints. The result of this life cycle analysis will enhance the advantages of the former solution in regards to the economic and environmental aspects.

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    FULLTEXT01
  • 8.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    ISISE, Department of Civil Engineering, University of Coimbra.
    Axial Force And Deformation Of A Restrained Steel Beam In Fire: Description and validation of a simplified analytical procedure2016In: Advanced steel construction, ISSN 1816-112X, Vol. 12, no 2, p. 174-193, article id 6Article in journal (Refereed)
    Abstract [en]

    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.

  • 9.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Numerical Study of Steel Beams in Sub-frame Assembly: Validation of Existing Hand Calculation Procedures2015In: Proceedings of International Conference on Applications of Structural Fire Engineering: Prague, Czech Repiublic ., 19-20 April 2013, 2015, Vol. 6, p. 272-277Conference paper (Refereed)
  • 10.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Numerical Study of Steel Beams in Sub-frame Assembly Validation of Existing Hand Calculation Procedures2015In: Journal of Structural Fire Engineering, ISSN 2040-2317, E-ISSN 2040-2325, Vol. 6, no 2, p. 123-140, article id 4Article in journal (Refereed)
    Abstract [en]

    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).

  • 11.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Steel beam behaviour in standard and natural fires: Comparison of FE modelling and hand calculation procedures2014In: Eurosteel 2014: 7th European Conference on Steel and Composite Structures, September 10-12, 2014, Naples, Italy / [ed] Raffaele Landolfo; Federico M. Mazzolani, Brussels: European Convention for Constructional Steelwork, ECCS , 2014Conference paper (Refereed)
  • 12.
    Iqbal, Naveed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Pavlovic, Marko
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Silva, Luís Simões da
    Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Numerical Investigation of the Behaviour of Steel Beams in Steel-Concrete Composite Frames2016In: Composite Construction in Steel and Concrete VII / [ed] Mark Bradford; Brian Uy, New York: American Society of Civil Engineers (ASCE), 2016, p. 199-213Conference paper (Refereed)
  • 13.
    Lopes, Fernanda
    et al.
    University of Coimbra, Department of Civil Engineering.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra, University of Coimbra, Department of Civil Engineering.
    Silva, Luís Simões da
    Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Silva, José Guilherme Santos da
    State University of Rio de Janeiro.
    Sub-frames with reverse channel connectiolns to CFT composite columns: experimental evaluation2015In: Advanced steel construction, ISSN 1816-112X, Vol. 11, no 1, p. 111-126Article in journal (Refereed)
    Abstract [en]

    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.

  • 14.
    Sandström, Joakim
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sjöström, Johan
    SP Sveriges Tekniska Forskningsinstitut, Brandteknik.
    Sundelin, Johan
    Fastec Sverige AB.
    Steel truss exposed to localized fires: Experimental report from a large scale experiment with a steel truss exposed to localized fires2015Report (Other academic)
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    FULLTEXT01
  • 15.
    Silva, Luís Simões da
    et al.
    Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
    Santiago, Aldina
    ISISE, Department of Civil Engineering, University of Coimbra.
    Lopes, Fernanda
    University of Coimbra, Department of Civil Engineering.
    Heistermann, Tim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Iqbal, Naveed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wald, František
    Czech Technical University in Prague.
    Jána, Tomáš
    Czech Technical University in Prague.
    Davisons, Buick
    University of Sheffield.
    Burgess, Ian
    University of Sheffield.
    Huang, Shan-Shan
    University of Sheffield.
    Dong, Gang
    University of Sheffield.
    Wang, Yong
    University of Manchester.
    Mandals, Parthasarathi
    University of Manchester.
    Jafarian, Mostafa
    University of Manchester.
    Skorepa, Martin
    Desmo a.s..
    Velda, Petr
    Desmo a.s..
    Koutlas, George
    Tata Steel, UK.
    Design of composite joints for improved fire robustness (Compfire): final report2014Report (Refereed)
1 - 15 of 15
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