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 presented yesterday to the fire group at Edinburgh about my PhD research. This was part of a series of presentations academics in the group are giving about their PhDs. It was also pretty much my last contribution at Edinburgh before I join Manchester University after Christmas. My slides are available here.
How is a circle defined? Something like
“A shape that is the set of all points on a plane equidistant from a given point (the centre).”
This effectively describes a circle as a shape having a constant radius. It is tempting to assume that a shape with constant diameter is therefore also a circle but this is not necessarily true. Continue reading
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