Advances in Structural Engineering Research
340986 - Pole Breakaway Joints – Feasibility Analysis
Saturday, April 21
10:00 AM - 11:30 AM
This paper will present a feasibility study to show applicability of High-fidelity, Physics-based (HFPB) simulations to screen performance of breakaway joints for highway light poles. Light poles are structures designed to support varying luminaire configurations as well as other attachments such as signs and traffic cameras. A light pole is an engineered structure sufficiently strong to withstand physical forces and capable of providing a long and relatively maintenance-free service life. Their primary function is, however, to resist the combinations of luminaire weight and ice and wind forces which poles may encounter over their expected life.
On the other hand, rigidly connected posts near traffic lanes are potential hazards for vehicles leaving the roadway unintendedly and colliding with the pole. The AASHTO Manual for Assessing Safety Hardware (MASH) discusses safety devices for light poles that need to be installed in most circumstances. For light poles, a breakaway device needs to be installed that provides a controlled failure mechanism that is activated when a vehicle collides with the pole. Such a breakaway device usually consists of a lower and upper part connected by bolts and a thin, metal plate that serves as the “fuse” providing the required controlled failure.
New systems are continually emerging to address safety problems and performance of existing devices needs to be reevaluated in the context of a changing vehicle fleet, the emergence of new materials and other factors. New systems are crash tested for compliance with safety criteria but recent advances in dynamic finite element analysis have allowed considerable modeling and simulation of vehicle impacts with roadside hardware. Although full scale crashworthiness testing will continue to be the most common method of evaluating impact performance of safety hardware, such testing is expensive and does not lend itself to investigation of multiple design alternatives. The advantage of simulation is its ability to isolate the effects of individual parameters from the multitude of possible conditions and to develop guidelines for roadside safety features representing the ‘state-of-the-possible’.
This paper will present a feasibility study to show applicability of High-fidelity, Physics-based (HFPB) simulations to screen performance of breakaway joints for highway light poles. The performance of light poles will be analyzed when impacted by two vehicle types: a full size passenger car and a full size pickup truck. Judicious use of computational modeling and simulation results in shorter design cycles and only requires physical testing for confirmation of compliance. Lessons learned from the study presented in this paper can be applied to other devices that rely on controlled ductile failure for performance such as being used in protective structures.