A hybrid approach to the transient collapse analysis of thin walled frameworks II Original Research Article

A new improved compound beam element (CBE2) for the transient hybrid finite element analysis is presented. The element is a combination of an elastic beam and two non-linear rotary springs whose behaviour in the elastic/plastic and deep collapse range is controlled by inputted moment-rotation curves and a load interaction curve. The formulation is based on the rigid convected coordinate procedure similar to the one used by the Belytschko-Schwer (B-S) beam element. The element stiffness matrix has been derived and its dependency on the spring behaviour explained. Two series of experiments were performed on two simple structures providing the data for the element performance evaluation. The tests performed were designed so that structural components collapse under biaxial bending and torsion. The tests results have shown, not only that CBE2 is more accurate than CBE1 but also that it does not suffer from the stability problems present in the formulation of CBE1 [1].