Façades: Regular pattern (Dezeen.com) and random pattern (Homedit.com); random perforations in bridge deck (greisch.com); perforated stairs (uztextil.info)
Steel is a very strong and ductile essential material that has been used in structures, through the ages, all over the globe. In 1913, in Sheffield, a ‘rustless’ material containing at least 11% of Chromium in mass, today commonly called stainless steel, was invented by Harry Brearley. It has mechanical characteristics (in terms of strength and ductility) reasonably similar to traditional carbon steel equivalents. It was mostly used in architectural ‘signature’ buildings skins. However, its inherent resistance to corrosion also makes it ideal for structures in corrosive environments such as in civil structures (bridges or building façades) facing the sea or in industries where structural components are in contact with chemicals. In addition, stainless steel is indefinitely recyclable (cradle-to-cradle material) and can convert to anything conceivable, and, while it is recycled, it doesn’t lose its performance. This benefits the environment by reducing the depletion of non-renewable resources, reducing the energy consumption in manufacturing, and avoiding end-of-life disposal impacts.
Depending on the Chromium content, one can cite three different families of stainless steel that are used in structures: ferritic, austenitic and duplex grades. Not only do these grades have different mechanical behaviours (mostly in terms of strength) but their stress-strain curves also differ substantially from that of traditional carbon steel (elastic-perfectly plastic). That is the reason why most design rules developed for carbon steel equivalents are not appropriate to stainless steel and that leads to inefficient design and un-rational use of material capacity. Realizing weight reduction is a very important driver for civil constructions and offshore installations to reduce material consumption, fabrication, transportation and erection costs, as well as environmental impacts. The introduction of new metals characterized by very high strengths and ductility range as well as re-sistance to corrosion allows reducing the weight of structures, provided that the structural behaviour can be well predicted in advance.
Over the past two decades, numerous experiments have been conducted on stainless steel components, made of different grades, looking at compression (buckling), bending (lateral-torsional buckling) or the combination of both as well as shear (shear buckling) or concentrated loading (web crippling). The results of those experiments are thoroughly described in the literature. Two main methods, well accepted by the scientific community, have also been developed to accurately design stainless steel structures: the Direct Strength Method (focusing on thin-walled sections and currently in the American code for steel components) and the Continuous Strength Method, extensively developed by the Imperial College London. There however remain today a number of issues that need solving in order to be able to efficiently design and rationally use stainless steel material’s capacity in structures.
One of these important problems is the behaviour of perforated architectural plated structures used in façades.
The most important problem is undeniably the buckling of such plates and how to accurately predict their critical failure load, depending on the pattern of perforations (regular or random) and their locations. The study will include experiments on perforated stainless steel plates in compression where deformations will be recorded using Digital Image Correlation. The results of these experiments will then be used to validate a geometrically nonlinear finite element model allowing to then study more configurations and patterns of perforations under different kind of loading encountered in reality. The research therefore involves both experimental and numerical works.
This studentship is funded through the UK Engineering and Physical Sciences Research Council (EPSRC) Doctoral Training Partnership and is open to both UK students (full award – fees plus stipend) and EU students (partial award – fees only). View full details of the EPSRC eligibility requirements.
Course fees are covered at the level set for UK/EU students (c. £7970 p.a.). The stipend (tax-free maintenance grant) is c. £15009 p.a. for the first year, and at least this amount for a further two and a half years.
Prospective candidates will be judged according to how well they meet the following criteria:
The following skills are desirable but not essential:
Informal enquiries are encouraged and should be addressed to Professor Rossi.
Candidates must submit a graduate application form and are expected to meet the graduate admissions criteria. Details are available on the course page of the University website.
Please quote 20ENGCI_BR in all correspondence and in your graduate applica-tion.
Noon on 24 January