Optimal sandwich beam design for deployable bridge

Abstract

There is a need for lightweight, short span bridges for military and civilian applications which has high mobility and easiness of erecting them in time of need for the Singapore Armed Forces. Currently, they are using Short Trackway Bridge system which has maximum weight of 250kg which is capable of supporting Military Load Class 30 vehicles.

The 4m composite sandwich bridge system presented in this report was designed for an alternative to the current deployable bridging system used by the Singapore Armed Forces. The proposed bridge design analysis was based on both stiffness and strength constraints. Upon choosing the materials for the facesheet as high strength carbon/epoxy composite and polyvinylchloride foam for the core, the optimized thickness of the facesheet and the core is 2.8mm and 50.6cm respectively. With the improved design by placing composite materials at the front and the back of the core, in order to protect the core, the weight was calculated to be approximately 118kg.

A finite element model was developed to predict the deformation, normal stresses and shear stress of the sandwich bridge upon loading for both the original design and the improved design. Deformations were within expected maximum deflections and the stresses were within material failure strength. Recommendations and suggestions for future research and development of the structure are also provided based on this analysis.