Important research on the design and performance of water-resistant reinforced concrete structures is helping the industry control crack widths, and hence water leakage, by studying the effects of different reinforcement arrangements and wall restraints.
The Laing O’Rourke Centre for Systems Engineering and Innovation at Imperial College London was established to provide a focus for world-class teaching and research. Its long-term aspiration, as the name suggests, is to transform the way the industry thinks about systems engineering.
As engineering projects become ever more complex, the need for systems thinking from their inception and throughout delivery has become a prerequisite for a successful outcome. The centre aims to develop engineers with proven skills in a specific field of engineering, but knowledge of the systems approaches across others. Someone who fits this description perfectly is Marianna Micallef.
Marianna graduated as an architect and civil engineer from the University of Malta in 2006, giving her a sound understanding of both disciplines. ‘I have a passion for structural engineering and a strong appreciation of architecture. My degree gave me an excellent grounding in both,’ she enthuses.
Following four years in the industry in Malta, working on a broad mix of building types, from medium-height mixed-use developments through to residential projects, Marianna came to the UK to study for an MSc in advanced structural engineering at Imperial College London, before embarking on her PhD studies at the Laing O’Rourke Centre. Her research focuses on the design and performance of water-resistant reinforced concrete (RC) structures, such as underground tunnels and water tanks.
In particular, she studies concrete cracking in RC walls with edge restraints. The goal is to control crack widths, and hence water leakage, by studying the effects of different reinforcement arrangements and wall restraints.
When restrained, concrete cracks during setting and cooling because of its low-tensile strength. Steel reinforcement is used to control the width and spacing of cracks, in order to improve durability and prevent leakage. This is especially important in the design of water-resistant and underground RC structures.
Previous research has focused on predicting crack spacings and widths in RC designs. From an engineering perspective, the design assumptions and principles in Eurocode 2 (EC2) differ from those used in BS 8007, which was the previous UK building code. ‘The PhD research was motivated by the observation that EC2 can require significantly more reinforcement than BS 8007 to control crack widths, with commercial and practical implications. For some designs, so much reinforcement is needed that it is difficult to get concrete around it,’ explains Micallef.
The objective of the research is to increase the confidence with which engineers can predict crack widths and, ultimately, to improve the EC2 method for designing reinforcement to control crack widths. ‘It is envisaged that the research will lead to less onerous reinforcement requirements for crack control in edge-restrained RC sections, which in turn will lead to more cost-effective and buildable structures,’ she says.
As Marianna points out, there is considerable benefit in working alongside construction companies such as Laing O’Rourke in her research. ‘These are issues that Laing O’Rourke and others are encountering on site, so I hope that my studies will be of practical use. Insight from industry is extremely important, otherwise research can just be theoretical.’
As her four-year PhD draws to a close, Marianna is looking forward to the future – and the various opportunities ahead of her. ‘I wouldn’t rule out the idea of more research. I’ve really enjoyed my PhD. I think my studies have given me a broad set of skills which I can use in industry or academia. I certainly plan to stay in the sector and am open to all possibilities.’
For Marianna the built environment is a constant source of stimulation, reinforcing her passion for her work. ‘I draw a lot of inspiration from structures that have been built in the capital. The final product from the construction sector is a building that is used – often by many thousands of people. It’s amazing working in a place like London, to see so many beautiful buildings. And that’s down to the engineering companies that actually build them.’
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