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.
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