RMA are developing an engineering software tool called Equilibrium Finite Elements (EFE). We are currently concentrating on the lower-bound limit analysis of reinforced concrete slabs and ductile metallic plates.
Limit Analysis predicts the plastic collapse load of a structure. It utilises plasticity theory of which there are two forms known as the upper-bound and the lower-bound methods. A well known form of the upper-bound method is the yield-line technique where a collapse mechanism is postulated and the collapse load is then determined. Practitioners of this technique will know that collapse load thus calculated is strongly dependent on the postulated collapse mechanism and that it provides upper-bound or unsafe predictions. We are formulating the problem as a lower-bound method using the concept of strong equilibrium to provide predictions of the collapse load that are always less than (or equal) to the theoretical value, i.e. it is a safe method. Reinforced concrete slabs (or metallic plates) have been considered first as the calculation of ultimate strength is of interest to structural engineers designing bridge decks and floor slabs.
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