PROPAGATING INSTABILITIES IN LONG SHALLOW PANELS

The paper addresses instabilities that can affect long panels with arc h cross sections. It is demonstrated that in addition to the classical limit load and bifurcation buckling instabilities, such panels can al so develop instabilities that propagate. Such instabilities can be ini tiated from local imperfections or as a result of localization of defo rmation that follows buckling into one of the classical modes. The low est pressure required to sustain such a buckle in propagation can be e valuated from a simple but exact energy balance argument. For arches w ith reasonable rise this pressure is significantly lower than that req uired to initiate an instability in a geometrically intact structure.