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Publications (10 of 154) Show all publications
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
Pavlovic, M., Spremic, M., Markovic, Z. & Veljkovic, M. (2016). Headed Shear Studs versus High-Strength Bolts in Prefabricated Composite Decks (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. 687-702). New York: American Society of Civil Engineers (ASCE)
Open this publication in new window or tab >>Headed Shear Studs versus High-Strength Bolts in Prefabricated Composite Decks
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. 687-702Conference paper, Published paper (Refereed)
Abstract [en]

Prefabricated steel and concrete composite decks are an interesting option to improve competitiveness and sustainability of the composite structures. Longitudinal shear connection is usually established by grouped headed studs, but possible alternative solution is to use bolted shear connectors. Welded headed studs and bolts (grade 8.8) are experimentally examined in the push-out tests (four tests on each). The same arrangement and dimensions of shear connectors (16 mm diameter and 100 mm height above flange) are considered and their resistances and behaviour are compared. Experimental results showed that headed studs and bolted shear connectors have similar shear resistance, while headed studs are more ductile. FEA is performed by ABAQUS/Explicit solver with damage material models to get more insight into behaviour of the specimens. FEA shows rather good agreement with experimental results. Influence of the bolt to hole clearance on the behaviour of specimens with bolted shear connectors is analysed and discussed

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-28251 (URN)10.1061/9780784479735.052 (DOI)000389435700052 ()1fb9d78d-a58f-4587-a254-c5cdd0cffbe1 (Local ID)978-0-7844-7973-5 (ISBN)1fb9d78d-a58f-4587-a254-c5cdd0cffbe1 (Archive number)1fb9d78d-a58f-4587-a254-c5cdd0cffbe1 (OAI)
Conference
International Conference on Composite Construction in Steel and Concrete : 28/07/2013 - 31/07/2013
Note

Godkänd; 2016; 20160303 (andbra)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-08Bibliographically approved
Matos, R., Pinto, P. L., Rebelo, C., Gervásio, H. & Veljkovic, M. (2016). Improved design of tubular wind tower foundations using steel micropiles (ed.). Structure and Infrastructure Engineering, 12(9), 1038-1050
Open this publication in new window or tab >>Improved design of tubular wind tower foundations using steel micropiles
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2016 (English)In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 12, no 9, p. 1038-1050Article in journal (Refereed) Published
Abstract [en]

The constant increase in the wind power production leads to the need of higher wind towers, which brings up some questions regarding the effectiveness of tubular towers and respective foundations. This work focuses on the comparative structural design, life cycle behaviour and costs of onshore concrete shallow foundations for tubular wind towers (WT) when steel micropiles are used to improve resistance of the soil–structure interface (hybrid foundation). Typical wind loading for Turbine Class II and moderate seismicity (.25 g peak ground acceleration) is used to design and analyse 18 WT foundation case studies. This allows the comparison between shallow and hybrid foundations designed for three different hub heights and respective turbine rated power (80 m/2 MW, 100 m/3.6 MW and 150 m/5 MW) and for three different tubular tower solutions (steel, concrete and hybrid steel–concrete). The possible benefits of the solution using steel grouted micropiles are discussed in terms of potential environmental and economic impacts using life cycle analysis. The use of micropiles reveals to be an interesting solution to improve common shallow WT foundations since it allows the reduction of the dimensions of the foundation leading to significant environmental and cost benefits.

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-4055 (URN)10.1080/15732479.2015.1076853 (DOI)000379180200003 ()2-s2.0-84940543126 (Scopus ID)1eacdebb-a446-443c-b49a-d33e6dc12eaa (Local ID)1eacdebb-a446-443c-b49a-d33e6dc12eaa (Archive number)1eacdebb-a446-443c-b49a-d33e6dc12eaa (OAI)
Note

Validerad; 2016; Nivå 2; 20150902 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically 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
Tran, A. T., Veljkovic, M., Rebelo, C. & Silva, L. S. (2016). Resistance of cold-formed high strength steel circular and polygonal sections: Part 1: Experimental investigations (ed.). Paper presented at . Journal of constructional steel research, 120, 245-257
Open this publication in new window or tab >>Resistance of cold-formed high strength steel circular and polygonal sections: Part 1: Experimental investigations
2016 (English)In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 120, p. 245-257Article in journal (Refereed) Published
Abstract [en]

This paper presents results from experiments performed on cold-formed high strength steel circular and polygonal sections. The test specimens were conceived to provide necessary information for development of tubular towers for wind turbines. A total of 32 high strength steel specimens were tested under uniaxial compression. Various thicknesses, openings and geometric imperfections were studied. Sixteen specimens without opening and sixteen specimens with opening were tested under axial compression in order to investigate influences of opening on the resistances. Tensile tests of coupon specimens taken from flat part, circular part and corner part were used to investigate basic properties of high strength steel material S650 and to evaluate influence of corner on the material strength and ductility. Initial geometric imperfections of the specimens were determined by using a 3D laser scanning method. The coupon test results were used to calibrate the ductile damage material models for modelling of fracture. Results from the experiments are fully described in this paper

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-6940 (URN)10.1016/j.jcsr.2015.10.014 (DOI)000374603200022 ()2-s2.0-84961589286 (Scopus ID)54549d2a-844f-412f-8a47-886dfba0bd03 (Local ID)54549d2a-844f-412f-8a47-886dfba0bd03 (Archive number)54549d2a-844f-412f-8a47-886dfba0bd03 (OAI)
Note
Validerad; 2016; Nivå 2; 20151027 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Tran, A. T., Veljkovic, M., Rebelo, C. & Silva, L. S. (2016). Resistance of cold-formed high strength steel circular and polygonal sections: Part 2: Numerical investigations (ed.). Journal of constructional steel research, 125, 227-238
Open this publication in new window or tab >>Resistance of cold-formed high strength steel circular and polygonal sections: Part 2: Numerical investigations
2016 (English)In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 125, p. 227-238Article in journal (Refereed) Published
Abstract [en]

This paper is the second part of the study on the cold-formed high strength steel circular and polygonal sections intended to be used in tubular wind towers. Results from 32 numerical finite element analysis (FEA) models were compared with and calibrated against results of the tests on 32 corresponding specimens. The FEA results agreed well with the experimental results in terms of resistances and load-displacement curves. Further investigations on the numerical models were performed. Yield stress used in the FEA significantly affected the resistances of the numerical models. Using 0.2% proof stress leaded to higher resistance than the experimental results. Corners significantly influenced buckling behaviour in the polygonal section models. Analyses of an oval opening in the tubular specimens showed that peak stresses around the opening were considerably higher in the polygonal section models than in the circular section models. Finally, investigation of sensitivity to geometrical imperfections indicated that failure modes of numerical models with geometrical imperfections according to EC3 significantly differed from those of tested specimens and numerical models with geometrical imperfections obtained from the 3D scans.

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-7640 (URN)10.1016/j.jcsr.2016.06.014 (DOI)000381834200017 ()2-s2.0-84976871845 (Scopus ID)60a8f640-4371-4b15-a819-88e3073103a4 (Local ID)60a8f640-4371-4b15-a819-88e3073103a4 (Archive number)60a8f640-4371-4b15-a819-88e3073103a4 (OAI)
Note

Validerad; 2016; Nivå 2; 20160705 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Koltsakis, E., Noury, P. & Veljkovic, M. (2016). The Contact Problem of Roller Bearings: Investigation of Observed Failures. Structural Engineering International, 26(3), 207-215
Open this publication in new window or tab >>The Contact Problem of Roller Bearings: Investigation of Observed Failures
2016 (English)In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 26, no 3, p. 207-215Article in journal (Refereed) Published
Abstract [en]

The present paper addresses how the commonly used Hertz formulas for contact stresses underestimate the actual stresses seen in practice due to temperature differentials, misalignments and other contruction-related defects. First, two failure cases of Swedish bridge roller bearings are analyzed and discussed; then, a detailed finite element (FE) model is used to investigate the accuracy of the traditional roller bearing design rules in view of issues such as abutment and girder deformability, misalignment imperfections and material nonlinearity. The bearing capacity of the studied rollers as provided by the manufacturer is used as reference. A rigorous FE model that accurately models girder, roller assembly and abutment provides the necessary information for the assessment of the related contact stresses, which were traditionally calculated by means of the Hertz analytical formulas. Numerical results first establish that roller bearings develop contact stress concentrations at the outer edges of the cylindrical drums. Second, it is established that the contact stresses are very sensitive to misalignment imperfections between the bridge girder and the abutment. Last, it is shown that the roller bearings develop inelastic deformation at relatively low loads in relation to the design load. These reasons, combined with the unlikelihood for roller bearings to shake-down, constitute the basis of the observed roller bearing failures.

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-60309 (URN)10.2749/101686616X14555429843762 (DOI)000386695500003 ()2-s2.0-84997850241 (Scopus ID)
Note

Validerad; 2016; Nivå 2; 2016-11-21(andbra)

Available from: 2016-11-11 Created: 2016-11-11 Last updated: 2018-07-10Bibliographically approved
Tran, A. T., Veljkovic, M., Rebelo, C. & Silva, L. S. (2015). Buckling Observation of Door Openings for Wind Turbine Towers (ed.). In: (Ed.), (Ed.), Nordic Steel Construction Conference 2015: Tampere, Finland, 23-25 September 2015. Paper presented at Nordic Steel Construction Conference : 23/09/2015 - 25/09/2015.
Open this publication in new window or tab >>Buckling Observation of Door Openings for Wind Turbine Towers
2015 (English)In: Nordic Steel Construction Conference 2015: Tampere, Finland, 23-25 September 2015, 2015Conference paper, Published paper (Refereed)
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-29255 (URN)2ab52dd7-a670-4210-b598-6e099f637a05 (Local ID)978-952-15-3578-9 (ISBN)978-952-15-3579-6 (ISBN)2ab52dd7-a670-4210-b598-6e099f637a05 (Archive number)2ab52dd7-a670-4210-b598-6e099f637a05 (OAI)
Conference
Nordic Steel Construction Conference : 23/09/2015 - 25/09/2015
Note
Godkänd; 2015; 20150929 (anhtra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-08Bibliographically approved
Pavlović, M., Manoleas, P., Veljkovic, M. & Koltsakis, E. (2015). Calibration of the Ductile Damage Material Model Parameters for a High Strength Steel (ed.). In: (Ed.), Markku Heinisuo; Jari Mäkinen (Ed.), The 13th Nordic Steel Construction Conference: NSCC-2015. Paper presented at Nordic Steel Construction Conference : 23/09/2015 - 25/09/2015 (pp. 231-232). Tampere: Tampere University of Technology, Department of Civil Engineering
Open this publication in new window or tab >>Calibration of the Ductile Damage Material Model Parameters for a High Strength Steel
2015 (English)In: The 13th Nordic Steel Construction Conference: NSCC-2015 / [ed] Markku Heinisuo; Jari Mäkinen, Tampere: Tampere University of Technology, Department of Civil Engineering , 2015, p. 231-232Conference paper, Meeting abstract (Refereed)
Abstract [en]

The on-going RUOSTE project aims to improve understanding of HSS by means of tests and FEA, addressing issues of ductility and stability of structures made of HSS. Various material models used in FEA are verified by tests. This paper presents calibration and verifica-tion of ductile damage material model in Abaqus FE software package referring to series of tensile test experiments on coupons and plate specimens with a single circular hole. Nominal steel grade S700MC and S960Q are used. Damage initiation criterion and evolution law are derived analysing localization of plasticity by FEA. Quasi-static analysis using explicit dy-namic solver is chosen in order to create the most realistic FEA of the specimens.

Place, publisher, year, edition, pages
Tampere: Tampere University of Technology, Department of Civil Engineering, 2015
Keywords
High Strength Steel, Ductile Damage Material, Engineering mechanics - Construction engineering, Materials science - Construction materials, Teknisk mekanik - Konstruktionsteknik, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-37833 (URN)bfad9e48-b179-4c27-a574-f185cbaff20d (Local ID)978-952-15-3578-9 (ISBN)978-952-15-3579-6 (ISBN)bfad9e48-b179-4c27-a574-f185cbaff20d (Archive number)bfad9e48-b179-4c27-a574-f185cbaff20d (OAI)
Conference
Nordic Steel Construction Conference : 23/09/2015 - 25/09/2015
Note
Godkänd; 2015; 20151002 (manpan)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-06-08Bibliographically approved
Pavlovic, M., Heistermann, C., Veljkovic, M., Pak, D., Feldmann, M., Rebelo, C. & Silva, L. S. (2015). Connections in towers for wind converters: part I: Evaluation of down-scaled experiments (ed.). Paper presented at . Journal of constructional steel research, 115, 445-457
Open this publication in new window or tab >>Connections in towers for wind converters: part I: Evaluation of down-scaled experiments
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2015 (English)In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 115, p. 445-457Article in journal (Refereed) Published
Abstract [en]

The cost of a tubular steel tower supporting a wind converter becomes increasingly important in a competitive energy market. In-situ connection between tower segments is an important factor of the design. The tower segments are usually connected by welded ring flanges. An alternative solution based on a novel single lap friction connection is analysed. The purpose of the research presented in this paper is to thoroughly analyse the behaviour of both connections by an experimental testing programme and advanced finite element analysis (FEA). Down-scaled experiments of ring flange and friction connection in circular towers were performed using a 4-point bending test set-up. Altogether eight connections joining cylindrical shell, 1 m diameter, plate thickness 8 mm and total span of about 7 m were tested. A friction connection with long open slotted holes and two different cases of the ring flange connection are considered: with perfectly flat flanges and flanges with geometric imperfection. Results of advanced quasi-static FEA, using explicit dynamic solver and ductile damage material model for bolts, are compared to experiments. Failure modes, bolt forces and distribution of meridional membrane stresses in the shell in the vicinity of connections are analysed. Existing hand-calculation models, for the bolt force and normal stress distribution in the shell are validated by experiments and FEA.

National Category
Building Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-2614 (URN)10.1016/j.jcsr.2015.09.002 (DOI)000364617800035 ()2-s2.0-84944159014 (Scopus ID)04086828-6636-41e8-9ce9-6e0443483b5f (Local ID)04086828-6636-41e8-9ce9-6e0443483b5f (Archive number)04086828-6636-41e8-9ce9-6e0443483b5f (OAI)
Note
Validerad; 2015; Nivå 2; 20151001 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4791-2341

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