Base geometry influence on impact load failure of a traffic signal pole

• Simulated bus impacting traffic signal pole in 3D finite element analysis.
• Simulations of varying thicknesses of pole or height of back-up ring.
• Failure occurs at high stress concentration at top height of inner back-up ring.
• Failure predicted to occur at point of impact with greater back-up ring height.

A galvanized tapered steel traffic signal pole impacted by a flat-front school bus was found not to break away at the base anchors bolts, but instead fail within the pole tube at a unique height associated with an inner back-up ring component. This failure was simulated with a 3D finite element model. The model was also used to investigate deformation and failure for various front bus shapes, pole thicknesses, and inner back-up ring heights. A higher back-up ring was found to delay failure at the point of impact, but in every case, the traffic signal pole always failed from the bus impact and associated impact load.