ProfessorTim Wilkinson

Project Opportunities

Title: Behaviour of LiteSteel Beams (Hollow Flange Channels)

Summary of opportunity:

This project involves the researching the structural behaviour of LiteSteel Beams.

Opportunity synopsis:

Smorgon Steel have developed a new range of cold-formed steel sections using a patented Dual Electric Resistance Weld technique. This allows the production of structural shapes similar to those of traditional hot-rolled steel sections but with hollow flanges - which increase the torsional stiffness of the section. The result is a hollow flange channel section, which has is being marketed as the LiteSteel Beam.

The Department of Civil Engineering and Smorgon Steel were awarded an Australian Research Council Linkage Grant to research the structural behaviour of these new sections. The main aim has been to identify the specific areas in which these sections would behave differently to normal cold-formed sections, and then investigate this behaviour. It was identified that the behaviour under bearing, bending moment and connections would require research. Other structural actions, such as compression, are being researched, in order to take advantage of the higher material strength in the weld.This research involves experimental investigations and finite element analysis. A team of researchers are examining the various aspects of the behaviour.

Bearing Capacity: Tests on different orientations of joists and girders are assessing the bearing strength of the sections. Complexity is involved in the interaction between flange crushing and web crippling modes. Assessment of some simple stiffening/strengthening menthods is also being carried out.

Connections: Research on the connection behaviour of LSBs has begun. The initial program is to research connection behaviour using traditional connection methods of bolting, with subsequent research to consider connectors such as screws and nails which can be used more easily on the construction site.

Compression: The unique shape of the LSB gives the hollow flange of the section a higher yield stress than the web. Research is being undertaken to capitalise and quantify the strength enhancement that this can provide.

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Project Opportunities

Title: Structural Steel Hollow Section Connections

Summary of opportunity:

This project has been performed in conjunction with Smorgon Steel Tube Mills over a number of years and carried out predominately by undergraduate thesis students. The aim has been to compare hollow section connection behaviour with current Australian design practice, and where possible devise new formulations.

Opportunity synopsis:

The shape of hollow sections with the ability to only access one side of the section easily make the design of connections more complex than that of traditional I-shaped sections. In addition, design recommendations for some hollow section connections have been based on models for I-shaped sections when it is difficult to determine if the same design methodology can be extrapolated to hollow sections.Some of the publications related to this research include:

*Wilkinson T., Daniels A, Wilton M, Wood (2005), “Uplift Tests On Column Base Plate Connections”, Advances in Steel Structures, Proceedings, 4th International Conference on Advances in Steel Structures, Shanghai, December 2005, (Elsevier, publ.).

*Wilkinson T., Petrovski T., Bechara E., and Rubal M., (2002), “Experimental Investigation of Slot Lengths in RHS Bracing Members”, Advances in Steel Structures, Proceedings, 3rd International Conference on Advances in Steel Structures, Hong Kong, December 2002, (Elsevier, publ.), (Chan, Teng and Chung eds.), pp 205 - 212.

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Project Opportunities

Title: Section Classification & b/t Limits for Hollow Sections

Summary of opportunity:

Most of the current b/t limitations in international steel design standards are based on investigations of hot-rolled I-sections. This project has been examining the behaviour of hollow sections, such as RHS and SHS to examine their classifications.To date, there have been bending only tests on SHS and RHS, as well as bending and compression tests on SHS and RHS in both the Class 1 and Class 2 range. Finite element simulation has also been performed.

Opportunity synopsis:

When a beam has suitable lateral bracing, its strength is usually governed by local buckling of the individual plate elements that make up the cross-section. A section is classified according to its moment capacity with respect to the fully plastic moment (Mp) and the yield moment (My) and the rotation capacity. A beam cross-section that can resist the plastic moment, and has a sufficiently large rotation capacity to be deemed suitable for plastic design is sometimes call a “Class 1” or “plastic” or “compact” section depending on the terminology of the relevant specification.

Local buckling is primarily a function of the slenderness of the individual plate elements, usually referred to as the b/t ratio. Design standards specify slenderness limits against which the b/t values are compared in order to classify a cross-section. These limits change according to the stress distribution and support conditions experienced by the element under consideration. Some of the publications related to this research include:

*Wilkinson T. and Hancock G. J., (2002), “Predicting the rotation capacity of cold-formed RHS beams using finite element analysis”, Journal of Constructional Steel Research, Elsevier, Vol 58, No 11, November 2002, pp 1455 - 1471.

*Wilkinson T. and Hancock G. J., (2000), “Tests to examine plastic behavior of knee joints in cold formed RHS”, Journal of Structural Engineering, American Society of Civil Engineers, Vol 126, No 3, March 2000, pp 297 305.

*Wilkinson T., (2003), “Recommendations for Cold-Formed RHS in Bending and Compression”, Tubular Structures X, Proceedings of the 10th International Symposium on Tubular Structures, Madrid Spain, (Balkema, publ.), (Jaurrieta, Alonso & Chica eds.), pp 293 300.

*Wood K. and Wilkinson T., (2003), “Measuring Imperfections in Hollow Sections”, Tubular Structures X, Proceedings of the 10th International Symposium on Tubular Structures, Madrid Spain, (Balkema, publ.), (Jaurrieta, Alonso & Chica eds.), pp 285-292

*Jouaux R & Wilkinson T, (2005), "Tests To Examine The Effect Of Axial Compression On The Rotation Capacity Of Square Hollow Sections", ICASS05, 5th International Conference on Advances in Steel Structures, Shanghai, China

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Project Opportunities

Title: Connections in high strength cold-formed rectangular hollow sections

Summary of opportunity:

A scholarship is available for a suitably qualified student with an Honours degree (or equivalent) in Engineering to undertake full time research leading to a PhD degree in the field of Connections in high strength cold-formed rectangular hollow sections. The scholarship is supported by an industry grant. This aim of this project is to determine design rules for the static strength of RHS truss connections in high strength (450 MPa) cold-formed steel.  This will be performed through laboratory experiments and finite element analysis.  This project may also establish joint design rules for higher strength hot-formed steels. Applicants must have a good degree in engineering and an interest in structural engineering. The scholarship stipend is $26.000 per annum in the first year, and may be held for three years subject to satisfactory progress. International students can apply but the scholarship does not cover any tuition fees. Separate tuition fee scholarships may be provided for international students from the School of Civil Engineering.  Further information can be obtained from Dr Tim Wilkinson, School of Civil Engineering, The University of Sydney, NSW 2006. (Phone: 0293515104, Email: t.wilkinson@usyd.edu.au). Applications including a full curriculum vitae, a copy of an academic transcript, and the names and contact details of at least two referees should be sent to Dr Wilkinson at the above address. Closing date: until the position is filled.Applications including a full curriculum vitae, a copy of an academic transcript, and the names and contact details of at least two referees should be sent to Dr Wilkinson at the above address.

Opportunity synopsis:

This project will investigate the strength limitation of fy = 355 MPa and fy/fu < 0.8 for static design of RHS truss connections (such as K, T, Y).  The current validity ranges of several CIDECT design models exclude the high strength Grade C450 (fy = 450 MPa) cold-formed steels.  The project therefore seeks to clarify or extend the current validity range of the present design models, or determine new design equations for the higher strength steels.  It is anticipated that the effect of the different material properties of higher strength steels and the investigation of different welding procedures will be integral parts of the project.

CIDECT design recommendations appear in various formats in different international documents (CIDECT design guide, Packer & Henderson, AISC (US) LRFD for SHSS, AISC (Australia), Eurocode 3) which contain a strength limitation of fy = 355 MPa and fy/fu &lt; 0.8 for several RHS truss connections (such as K, T, Y), and were generally based on tests on hot finished products.  More recent research projects, many sponsored by CIDECT, such as those at Sydney & Monash (Australia), Karlsruhe (Germany), Delft (Netherlands), Toronto (Canada), have begun to investigate higher strength and cold formed steels, but there is a definite gap in design knowledge for high strength cold-formed steels.CIDECT members Smorgon Steel Tube Mills, OneSteel & Rautaruukki almost exclusively produce cold-formed tubular sections, while other CIDECT members are producing increasing quantities of cold-formed steels.  The extension of validity ranges for connections will allow designers to take full benefit of the strength enhancement afforded by cold forming.  Developing design rules to permit them to be more effective will increase their use.  It may also be possible for the project extend the validity of the design rules for high strength hot-formed tubes.

----------Current Research Projects----------

• Structural Behaviour of Hollow Flange Channels
• Local Buckling of Structural Steel Hollow Sections
• Connections in Steel Structures