The influence of intermediate diaphragms in overhead travelling crane box-girders.

Intermediate diaphragms are invariably included in the design of overhead travelling crane box-girders. This study concerns the influence of these diaphragms and their spacing on the global characteristic behaviour of the girder. In particular the action of internal diaphragms in the control of stresses associated with distortional deformation is investigated. The details and results of experimental tests on scale models of two crane geometries are presented. A method of analysis is developed to describe the distortional deformation of crane box-girder geometries using discrete box section elements. This method is assessed by comparison with both the experimental results and finite element analysis conducted for a range of configurations. It is shown to produce adequate predictions for use in further investigations. The theory is applied (by means of computer analysis of different crane box arrangements) to perform a study of the influence of intermediate diaphragms on both transverse distortional bending and longitudinal distortional warping. The results of this study are then incorperated into a series of design recommendations for the selection of cross section geometry and the positioning of diaphragms with particular reference to the control of these distortional effects.