Like most materials, when you heat a piece of concrete, it expands. Unlike most materials, when you heat a piece of concrete with a load on it, it expands less, or not at all, or it may even contract, depending on how big the load is – diagram below. This unusual behaviour goes by a number of names such transient thermal strain, transient thermal creep, or load-induced thermal strain (LITS). Here I will use LITS.
LITS – in simple terms. Concrete thermal expansion is stress dependent.
My interest in LITS began about eight years ago when then PhD student, Angus Law, started investigating its role in concrete-framed structures under fire. Angus implemented a LITS model in Abaqus and showed that LITS can affect the behaviour of certain types of structural element substantially. He also demonstrated the importance of correctly representing the multi-axial behaviour of LITS.
More recently two more PhD students working with me have started looking at LITS from very different angles: Continue reading
I recently set a piece of coursework for the Structures 1 course I run asking students to , “…identify study and research the behaviour and design of an existing structure. Present your findings on a maximum of two sides of A4 or equivalent (e.g. 1 side of A3, or a short video or any other means of communication)..” This resulted in many good submissions and analyses of structures ranging from park benches to cranes to bridges. One highly creative video submission looked at a structure similar to about 7 billion others. Me!! Among other things it appears I am about 1% shorter in the afternoon than in the evening. I think this is a great example of engineering communication – well done to Robert Cushworth, Hamish Mayall, Jordan Lowrey and Jake Wheeler
I normally only run one competition a year but since I have moved to Manchester and my Christmas competition wasn’t advertised here, this year there will be two. Here it is – my Easter Competition.
I have been working for several years now with Guillermo Rein, Angus Law, Jamie Stern-Gottfried and others on “travelling fires” for structural design – that is, design fires where it is not assumed that the temperature remains the same in all parts of a fire compartment. This research has been highly successful and resulted in prizes and journal publications. However, for me, there remains a problem – the temperature of the travelling design fire is too hot! Continue reading