Publications


Scholar profiles:

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RG           RI           SC


Journal publications:

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Joao Pedro Martins, Ashkan Shahbazian, Luís Simões da Silva, Carlos Rebelo, Rui Simões (2016) Structural behaviour of prestressed stayed columns with single and double cross-arms using normal and high strength steel, Archives of Civil and Mechanical Engineering, Volume 16, Issue 4, September 2016, Pages 618–633.
Link to paper

Abstract:

One solution to improve load carrying capacity of slender columns is to add prestressed cables and cross-arms as they provide additional restraints along the length. Such columns are called prestressed stayed columns (PSSC). This solution is very effective, but there are no experimental results on long columns which is a practical case for such columns. This paper presents the results of an experimental study on 18 m PSSC with single and double cross-arms along the length and using normal and high strength steel. In total, 77 tests were carried out to investigate the structural behaviour of such systems and improvements made by using high strength steel and stay systems. The results in this paper provide detailed data on the behaviour of realistic PSSC which was not available before and highlight the advantages of the using high strength steel in such systems.

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Miguel Serra, Ashkan Shahbazian, Luís Simões da Silva, Liliana Marques, Carlos Rebelo, Pedro Colmar Gonçalves da Silva Vellasco (2015) A full scale experimental study of prestressed stayed columns, Engineering Structures, Volume 100, Pages 490-510.
Link to paper

Abstract:

This paper presents the results of an experimental study on 12 m prestressed stayed columns. In total, 44 tests were carried out to investigate the compressive strength and behaviour of such systems by varying column cross-section geometry, diameter of cables, initial pretension level of stays and steel grade. The details of material testing for both steel and cable, and the compressive strength of each specimen including a detailed analysis of results for further numerical and analytical investigations are presented. The applicability of available analytical and design methods for determining the elastic buckling load and the load carrying capacity of stayed columns was assessed. The results provide detailed data on the behaviour of realistic PSSC and highlight the importance of the imperfections and the benefits of such systems.

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Shahbazian A. and Wang, Y. C. (2014) A fire resistance design method for thin-walled steel studs in wall panel constructions exposed to parametric fires, Thin-Walled Structures, 77, pp.67-76.
Link to paper

Abstract:

This paper investigates the applicability of a simple fire resistance design method for axially loaded thin-walled steel studs in wall panel assemblies when exposed to parametric fires from one side. The simple method includes calculations of cross-section temperatures and ultimate load carrying capacities at elevated temperatures. The simplified calculation method for heat transfer in the cross-section is based on dividing the cross-section into a number of segments. The thermal properties of these layers are based on weighted averages of the thermal properties of the components contained within. The structural capacity calculation method is based on the Direct Strength Method. Results from the design method are compared with the results from Finite Element simulations for heat transfer and structural analysis (236 models). The calculation results are in good agreement with the simulation results and the proposed method may be used in performance-based fire engineering design of such construction.

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Shahbazian A. and Wang, Y. C. (2014) Performance-based fire resistance design method for wall panel assemblies using thin-walled steel sections, The Structural Engineer, 92, pp.51-56.
Link to paper

Abstract:

The advantages of cold-formed thin-walled steel studs are many and their application in building construction continues to grow. They are used as load-bearing members. An example is lightweight wall panel assemblies which consist of channel steel studs with gypsum plasterboard layers attached to the two flanges, often with interior insulation. At present, expensive fi re tests or advanced numerical modelling methods are necessary in order to obtain the fi re resistance of such wall assemblies. For common practice this is not effective and a simplifi ed method, suitable for use in daily design, is necessary. This paper explains a new approach for calculating key temperatures on the steel studs and describes the Direct Strength Method (DSM) for calculating the load-bearing capacity of cold-formed thin-walled steel studs with non-uniform temperature distributions in the cross-section, instead of using the traditional effective width method. Combining these two aspects gives a performance-based fi re resistant design method that can be used in the design or development of products.

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Shahbazian A. and Wang, Y. C. (2013) A simplified approach for calculating temperatures in axially loaded cold-formed thin-walled steel studs in wall panel assemblies exposed to fire from one side, Thin-Walled Structures,64, pp.60-72.
Link to paper

Abstract:

Cold-formed thin-walled steel sections are usually used as the load-bearing elements of wall panels in building construction. Such panels consist of channel steel sections with gypsum plasterboard layers attached to the flanges on the outside and interior insulation. This paper proposes a simple method to calculate temperature distributions in the steel section when the panel is exposed to fire from one side. This method calculates the average temperatures in the flanges of the steel section and assumes that the temperature in the web is linear. The proposed method is based on simple heat balance analysis for a few nodes representing the key components of the panel. The thermal resistance of these nodes is obtained from the weighted average of thermal resistances in an effective width of the panel within which heat transfer in the panel width direction is assumed to occur. The effective width of the panel for calculating the weighted average of thermal resistances can be taken as the steel section flange width plus 15% of the difference between 300 mm and the flange width of the steel section. Validity of the proposed method has been checked by comparison of the temperature results between the proposed 1-D modelling and 2-D ABAQUS Finite Element modelling for an extensive set of parametric and sensitivity studies covering different steel section dimensions (width, depth, thickness and lips), different spacing between steel section, number of gypsum layers (1 or 2) and different interior insulation properties. Further assessment of accuracy of the proposed temperature calculation method has been provided by comparing compressive resistance of the steel studs between using temperature profiles produced by 2-D ABAQUS Finite Element simulation and by using the proposed simplified method. Although the simplified method still requires a numerical procedure, it is extremely easy to implement to give designers of this structural system a much more efficient tool than using Finite Element simulations to calculate its fire resistance.

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Shahbazian A. and Wang, Y. C. (2012) Direct Strength Method for calculating distortional buckling capacity of cold-formed thin-walled steel columns with uniform and non-uniform elevated temperatures, Thin-Walled Structures,53, pp.188-199.
Link to paper

Abstract:

This paper assesses the applicability of the Direct Strength Method (DSM) to calculating the distortional buckling strength of cold-formed thin-walled (CF-TW) steel members with uniform and non-uniform elevated temperature distributions in the cross-section. The assessment was carried out by checking the DSM calculation results with numerical simulation results using the general finite element software ABAQUS which was further validated against ambient and uniform elevated temperature tests on short lipped channel sections, in addition to the author’s previous validation studies for thin-walled steel columns with non-uniform temperature distributions. The validated numerical model has been used to generate an extensive database (453) of numerical results of load carrying capacity of CF-TW members with different uniform and non-uniform temperature distributions in the cross-sections, under different boundary and loading conditions and with different dimensions and lengths. It is concluded that the existing DSM distortional buckling curve for ambient temperature application is also applicable for columns with uniform temperature distributions in the cross-section, but is un-conservative for columns with non-uniform temperature distributions in the cross-section. This paper proposes a modification to the distortional buckling curve to enable DSM to deal with distortional buckling in columns with non-uniform temperature distributions.

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Shahbazian A. and Wang, Y. C. (2011) Application of the Direct Strength Method to local buckling resistance of thin-walled steel members with non-uniform elevated temperatures under axial compression, Thin-Walled Structures,49(12), pp.1573-1583.
Link to paper

Abstract:

This paper assesses the applicability of the Direct Strength Method (DSM) to calculating the local buckling ultimate strength of cold-formed thin-walled (CF-TW) steel members with non-uniform elevated temperature distributions in the cross-section. The assessment was carried out by checking the DSM calculation results with numerical simulation results using the general finite element software ABAQUS which was validated against ambient and uniform elevated temperature tests on short lipped channel sections. The validated numerical model was used to generate an extensive database (372 models) of numerical results of load carry capacity of CF-TW members with different uniform and non-uniform temperature distributions in the cross-sections, under different boundary and loading conditions and with different dimensions and lengths. It was concluded that the DSM local buckling curve was directly applicable for columns with uniform temperature distributions in the cross-section. For columns with non-uniform temperature distributions, a modification to the local buckling curve was necessary and this paper has proposed a new curve.

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Shahbazian A. and Wang, Y. C. (2011) Calculating the global buckling resistance of thin-walled steel members with uniform and non-uniform elevated temperatures under axial compression, Thin-Walled Structures,49(11), pp.1415-1428.
Link to paper

Abstract:

This paper develops a method, based on the Direct Strength Method (DSM) global buckling curve, to calculate the global buckling ultimate strength of cold-formed thin-walled (CF-TW) steel members under uniform and non-uniform elevated temperatures. The assessment is carried out by checking the DSM curve-based results with numerical simulation results using the general finite element software ABAQUS. The numerical model has been validated against a series of ambient temperature and fire tests on panels made of two different lipped channel sections tested to their ultimate load carrying capacities at ambient temperature or to their fire resistance at different load levels. The validated numerical model has been used to generate a database of numerical results of load carry capacity of CF-TW members with different uniform and non-uniform temperature distributions in the cross-sections under different boundary and loading conditions and with different dimensions. It is concluded that the DSM global buckling column curve is directly applicable for uniform temperature but a simple modification is required for non-uniform temperature distributions.

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Shahbazian A. and Wang, Y. C. (2011) Fire resistance design method for cold-formed thin-walled steel structures, The Structural Engineer, 89(21), pp.10-12.
Link to paper


Conferences:

  • Poster Presentation, Young Members Conference 2011, the Institute of Structural Engineers, London, UK
    1st prize winner
  • Young Members’ Papers, Lancashire and Cheshire Regional Group, the Institute of Strucutural Engineers, Salford, UK
    Young Members’ Award (Jan 2012)
  • Shahbazian A. and Wang, Y. C. (2011) Fire resistance design method for cold-formed thin-walled steel columns, MACE Postgraduate Research Conference, Manchester, UK, The University of Manchester, pp.17-19. (Oral presentation)
  • Structures in Fire Forum, April 2012, London, UK
  • ASHKAN SHAHBAZIAN, FILIPPO GENTILI, RICARDO COSTA, CARLOS REBELO, LUIS S. SILVA, (2015), ADVANCED TOOLS FOR SIMULATING MONOTONIC AND CYCLIC RESPONSE OF BEAM TO COLUMN STEEL JOINTS, PROCEEDINGS OF X CONGRESSO DE CONSTRUÇÃO METÁLICA E MISTA, P. II-153 – II-160, COIMBRA. (ORAL PRESENTATION)
  • Filippo Gentili, Ashkan Shahbazian, Carlos Rebelo, Luis S. Silva, (2015), Influence of the joint modelling strategies on the seismic response of dual concetrically braced steel frames, Proceedings of X Congresso de Construção Metálica e Mista, p. II-603 – II-612, Coimbra, ISBN: 978-989-9922617. (oral presentation)
  • Ricardo Breda, João Pedro Martins, Ashkan Shahbazian, Luís Simões da Silva, (2015), Estudo experimental do comportamento de colunas pré-esforçadas de elevada esbelteza. Atas do X Congresso de Construção Metálica e Mista, pp. II-565 II-574, Coimbra. (oral presentation)