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Publications (10 of 14) Show all publications
Dogar, A. U., Rehman, H. M., Tafsirojjaman, T. & Iqbal, N. (2020). Experimental investigations on inelastic behaviour and modified Gerber joint for double-span steel trapezoidal sheeting. Structures, 24, 514-525
Open this publication in new window or tab >>Experimental investigations on inelastic behaviour and modified Gerber joint for double-span steel trapezoidal sheeting
2020 (English)In: Structures, ISSN 2352-0124, Vol. 24, p. 514-525Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Cold-formed steel, Trapezoidal sheeting, Inelastic behaviour, Post-elastic, Multi-span sheeting, Gerber joint, Direct strength method, Moment redistribution
National Category
Other Civil Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-77883 (URN)10.1016/j.istruc.2020.01.042 (DOI)000519625500040 ()2-s2.0-85079168642 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-04-02 (alebob)

Available from: 2020-02-26 Created: 2020-02-26 Last updated: 2020-04-02Bibliographically approved
Iqbal, N. (2016). Analysis of Catenary Effect in Steel Beams and Trusses Exposed to Fire (ed.). (Doctoral dissertation). Paper presented at . Luleå tekniska universitet
Open this publication in new window or tab >>Analysis of Catenary Effect in Steel Beams and Trusses Exposed to Fire
2016 (English)Doctoral 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.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016. p. 234
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-26191 (URN)d1905d06-543d-4be1-a5fd-ea79eeb232e8 (Local ID)978-91-7583-648-5 (ISBN)978-91-7583-649-2 (ISBN)d1905d06-543d-4be1-a5fd-ea79eeb232e8 (Archive number)d1905d06-543d-4be1-a5fd-ea79eeb232e8 (OAI)
Note

Godkänd; 2016; 20160808 (naviqb); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Naveed Iqbal Ämne: Stålbyggnad /Steel Structures Avhandling: Analysis of Catenary Effect in Steel Beams and Trusses Exposed to Fire Opponent: Professor Paulo Vila Real, Department of Civil Engineering, University of Aveiro, Aveiro, Portugal. Ordförande: Professor Milan Veljkovic, Avdelningen för byggkonstruktion och produktion, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet, Luleå. Tid: Tisdag 6 september 2016, kl 10.00 Plats: F531, Luleå tekniska universitet

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved
Iqbal, N., Heistermann, T., Veljkovic, M., Lopes, F., Santiago, A. & Silva, L. S. (2016). Axial Force And Deformation Of A Restrained Steel Beam In Fire: Description and validation of a simplified analytical procedure (ed.). Paper presented at . Advanced steel construction, 12(2), 174-193, Article ID 6.
Open this publication in new window or tab >>Axial Force And Deformation Of A Restrained Steel Beam In Fire: Description and validation of a simplified analytical procedure
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2016 (English)In: Advanced steel construction, ISSN 1816-112X, Vol. 12, no 2, p. 174-193, article id 6Article in journal (Refereed) Published
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.

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-2778 (URN)10.18057/IJASC.2016.12.2. (DOI)077788be-f28a-46f9-943e-cb9304d7eb37 (Local ID)077788be-f28a-46f9-943e-cb9304d7eb37 (Archive number)077788be-f28a-46f9-943e-cb9304d7eb37 (OAI)
Note
Validerad; 2016; Nivå 2; 20160615 (naviqb)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-08Bibliographically approved
Iqbal, N., Pavlovic, M., Veljkovic, M., Heistermann, T., Lopes, F., Santiago, A. & Silva, L. S. (2016). Numerical Investigation of the Behaviour of Steel Beams in Steel-Concrete Composite Frames (ed.). In: (Ed.), Mark Bradford; Brian Uy (Ed.), Composite Construction in Steel and Concrete VII: . Paper presented at International Conference on Composite Construction in Steel and Concrete : 28/07/2013 - 31/07/2013 (pp. 199-213). New York: American Society of Civil Engineers (ASCE)
Open this publication in new window or tab >>Numerical Investigation of the Behaviour of Steel Beams in Steel-Concrete Composite Frames
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2016 (English)In: 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, Published paper (Refereed)
Place, publisher, year, edition, pages
New York: American Society of Civil Engineers (ASCE), 2016
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-30890 (URN)10.1061/9780784479735.016 (DOI)000389435700016 ()4e099d07-6543-4706-8b25-ed77fd2518a3 (Local ID)978-0-7844-7973-5 (ISBN)4e099d07-6543-4706-8b25-ed77fd2518a3 (Archive number)4e099d07-6543-4706-8b25-ed77fd2518a3 (OAI)
Conference
International Conference on Composite Construction in Steel and Concrete : 28/07/2013 - 31/07/2013
Note

Godkänd; 2016; 20160223 (andbra)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-08Bibliographically approved
Iqbal, N., Heistermann, T., Veljkovic, M., Lopes, F., Santiago, A. & Silva, L. S. (2015). Numerical Study of Steel Beams in Sub-frame Assembly: Validation of Existing Hand Calculation Procedures (ed.). In: (Ed.), (Ed.), Proceedings of International Conference on Applications of Structural Fire Engineering: Prague, Czech Repiublic ., 19-20 April 2013. Paper presented at International Conference on Applications of Structural Fire Engineering : 19/04/2013 - 20/04/2013 (pp. 272-277). , 6
Open this publication in new window or tab >>Numerical Study of Steel Beams in Sub-frame Assembly: Validation of Existing Hand Calculation Procedures
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2015 (English)In: Proceedings of International Conference on Applications of Structural Fire Engineering: Prague, Czech Repiublic ., 19-20 April 2013, 2015, Vol. 6, p. 272-277Conference paper, Published paper (Refereed)
Series
Journal of Structural Fire Engineering, ISSN 2040-2317
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-39639 (URN)e7891e6c-24a8-4c72-b01a-4eb7f5f3050f (Local ID)e7891e6c-24a8-4c72-b01a-4eb7f5f3050f (Archive number)e7891e6c-24a8-4c72-b01a-4eb7f5f3050f (OAI)
Conference
International Conference on Applications of Structural Fire Engineering : 19/04/2013 - 20/04/2013
Note
Godkänd; 2015; 20151123 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-06-08Bibliographically approved
Iqbal, N., Heistermann, T., Veljkovic, M., Lopes, F., Santiago, A. & Silva, L. S. (2015). Numerical Study of Steel Beams in Sub-frame Assembly Validation of Existing Hand Calculation Procedures (ed.). Journal of Structural Fire Engineering, 6(2), 123-140, Article ID 4.
Open this publication in new window or tab >>Numerical Study of Steel Beams in Sub-frame Assembly Validation of Existing Hand Calculation Procedures
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2015 (English)In: 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) Published
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).

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-3501 (URN)10.1260/2040-2317.6.2.123 (DOI)1552a0ec-5224-46c9-aaa9-beacebd0125e (Local ID)1552a0ec-5224-46c9-aaa9-beacebd0125e (Archive number)1552a0ec-5224-46c9-aaa9-beacebd0125e (OAI)
Note

Validerad; 2015; Nivå 1; 20150524 (naviqb)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2020-03-05Bibliographically approved
Sandström, J., Wickström, U., Veljkovic, M., Iqbal, N., Sjöström, J. & Sundelin, J. (2015). Steel truss exposed to localized fires: Experimental report from a large scale experiment with a steel truss exposed to localized fires (ed.). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Steel truss exposed to localized fires: Experimental report from a large scale experiment with a steel truss exposed to localized fires
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2015 (English)Report (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2015. p. 53
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-22393 (URN)2b5d5d0b-2729-4ef2-93dc-f61f2cec67a1 (Local ID)2b5d5d0b-2729-4ef2-93dc-f61f2cec67a1 (Archive number)2b5d5d0b-2729-4ef2-93dc-f61f2cec67a1 (OAI)
Note
Godkänd; 2015; 20151001 (joasan)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-04-16Bibliographically approved
Lopes, F., Santiago, A., Silva, L. S., Iqbal, N., Veljkovic, M. & Silva, J. G. (2015). Sub-frames with reverse channel connectiolns to CFT composite columns: experimental evaluation (ed.). Advanced steel construction, 11(1), 111-126
Open this publication in new window or tab >>Sub-frames with reverse channel connectiolns to CFT composite columns: experimental evaluation
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2015 (English)In: Advanced steel construction, ISSN 1816-112X, Vol. 11, no 1, p. 111-126Article in journal (Refereed) Published
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.

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-13734 (URN)10.18057/IJASC.2015.11.1.7 (DOI)d031243e-f6cc-4005-9e10-d3965cde5122 (Local ID)d031243e-f6cc-4005-9e10-d3965cde5122 (Archive number)d031243e-f6cc-4005-9e10-d3965cde5122 (OAI)
Note

Validerad; 2015; Nivå 2; 20150320 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2020-03-06Bibliographically approved
Silva, L. S., Santiago, A., Lopes, F., Heistermann, T., Veljkovic, M., Iqbal, N., . . . Koutlas, G. (2014). Design of composite joints for improved fire robustness (Compfire): final report (ed.). Paper presented at . Luxembourg: Publications Office of the European Union
Open this publication in new window or tab >>Design of composite joints for improved fire robustness (Compfire): final report
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2014 (English)Report (Refereed)
Place, publisher, year, edition, pages
Luxembourg: Publications Office of the European Union, 2014. p. 184
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-23152 (URN)10.2777/76889 (DOI)5c6b4965-b799-4b25-9ed8-4d7c6f46a492 (Local ID)978-92-79-38568-1 (ISBN)5c6b4965-b799-4b25-9ed8-4d7c6f46a492 (Archive number)5c6b4965-b799-4b25-9ed8-4d7c6f46a492 (OAI)
Note
Godkänd; 2014; Bibliografisk uppgift: Grant Agreement RFSR-CT-2009-00021; 20151207 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-08Bibliographically approved
Iqbal, N., Heistermann, T., Veljkovic, M., Lopes, F., Santiago, A. & Silva, L. S. (2014). Steel beam behaviour in standard and natural fires: Comparison of FE modelling and hand calculation procedures (ed.). In: (Ed.), Raffaele Landolfo; Federico M. Mazzolani (Ed.), Eurosteel 2014: 7th European Conference on Steel and Composite Structures, September 10-12, 2014, Naples, Italy. Paper presented at European Conference on Steel and Composite Structures : 10/09/2014 - 12/09/2014. Brussels: European Convention for Constructional Steelwork, ECCS
Open this publication in new window or tab >>Steel beam behaviour in standard and natural fires: Comparison of FE modelling and hand calculation procedures
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2014 (English)In: 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, Published paper (Refereed)
Place, publisher, year, edition, pages
Brussels: European Convention for Constructional Steelwork, ECCS, 2014
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-27663 (URN)12dcf5b6-de4e-4a78-a4e5-a226f4a17248 (Local ID)9789291471218 (ISBN)12dcf5b6-de4e-4a78-a4e5-a226f4a17248 (Archive number)12dcf5b6-de4e-4a78-a4e5-a226f4a17248 (OAI)
Conference
European Conference on Steel and Composite Structures : 10/09/2014 - 12/09/2014
Note
Godkänd; 2014; 20150304 (timhei)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7286-5500

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