Semi-analytical tools for the Single Perturbation Load Approach using the Ritz Method

Abstract

Many structural components or launcher structures can be modelled using a conical or cylindrical-like set of shell equations. The current guidelines used at the preliminary design phase are perceived as conservative and do not take into account properly the stacking sequence of laminated shells. New guidelines has been developed for example by the NASA project Shell Buckling Knock-Down Factor (SBKDF) and by the European consortium DESICOS. One of the approaches currently investigated is the Single Perturbation Load Approach (SPLA), originally proposed by Christian Hühne (2008) which is based on the phenomena that the axially compressed shell buckling load gets nearly constant after a threshold of geometric imperfection caused by a lateral load, obtaining a convenient design load. A disadvantage of this method is that it requires many non-linear computations in order to find this load threshold. This study presents the development of semi-analytical tools that allow a fast prediction of the design load using the SPLA, with the aim to overcome the computational disadvantage of this method.